Displaying publications 1 - 20 of 108 in total

  1. Okuda S, Prince JP, Davis RE, Dally EL, Lee IM, Mogen B, et al.
    Plant Dis, 1997 Mar;81(3):301-305.
    PMID: 30861775 DOI: 10.1094/PDIS.1997.81.3.301
    Phytoplasmas (mycoplasmalike organisms, MLOs) associated with mitsuba (Japanese hone-wort) witches'-broom (JHW), garland chrysanthemum witches'-broom (GCW), eggplant dwarf (ED), tomato yellows (TY), marguerite yellows (MY), gentian witches'-broom (GW), and tsu-wabuki witches'-broom (TW) in Japan were investigated by polymerase chain reaction (PCR) amplification of DNA and restriction enzyme analysis of PCR products. The phytoplasmas could be separated into two groups, one containing strains JHW, GCW, ED, TY, and MY, and the other containing strains GW and TW, corresponding to two groups previously recognized on the basis of transmission by Macrosteles striifrons and Scleroracus flavopictus, respectively. The strains transmitted by M. striifrons were classified in 16S rRNA gene group 16SrI, which contains aster yellows and related phytoplasma strains. Strains GW and TW were classified in group 16SrIII, which contains phytoplasmas associated with peach X-disease, clover yellow edge, and related phytoplasmas. Digestion of amplified 16S rDNA with HpaII indicated that strains GW and TW were affiliated with subgroup 16SrIII-B, which contains clover yellow edge phytoplasma. All seven strains were distinguished from other phytoplasmas, including those associated with clover proliferation, ash yellows, elm yellows, and beet leafhopper-transmitted virescence in North America, and Malaysian periwinkle yellows and sweet potato witches'-broom in Asia.
  2. Ray JD, Subandiyah S, Prakoso AB, Rincon-Florez VA, Carvalhais LC, Drenth A
    Plant Dis, 2022 Jan 25.
    PMID: 35077223 DOI: 10.1094/PDIS-10-21-2373-RE
    Banana Blood disease is a bacterial wilt caused by Ralstonia syzygii subsp. celebesensis and is an economically important disease in Indonesia and Malaysia. Transmission of this pathogen is hypothesized to occur through insects mechanically transferring bacteria from diseased to healthy banana inflorescences, and other pathways involving pruning tools, water movement and root-to-root contact. This study demonstrates that the ooze from the infected male bell and the sap from various symptomatic plant parts are infective and the cut surfaces of a bunch peduncle, petiole, corm, and the rachis act as infection courts for R. syzygii subsp. celebesensis. In addition, evidence is provided that R. syzygii subsp. celebesensis is highly tool transmissible, that the bacterium can be transferred from the roots of a diseased plant to the roots of a healthy plant and transferred from the mother plant to the sucker. We provide evidence that local dispersal of Blood disease is predominantly through mechanical transmission by insects, birds, bats or human activities from diseased to healthy banana plants and that long-distance dispersal is through the movement of contaminated planting material. Disease management strategies to prevent crop losses associated with this emerging disease are discussed based on our findings.
  3. Liao TZ, Chen YH, Tsai JN, Chao C, Huang TP, Hong CF, et al.
    Plant Dis, 2023 Jul;107(7):2039-2053.
    PMID: 36428260 DOI: 10.1094/PDIS-06-22-1285-RE
    Brown root rot disease (BRRD), caused by Phellinus noxius, is an important tree disease in tropical and subtropical areas. To improve chemical control of BRRD and deter emergence of fungicide resistance in P. noxius, this study investigated control efficacies and systemic activities of fungicides with different modes of action. Fourteen fungicides with 11 different modes of action were tested for inhibitory effects in vitro on 39 P. noxius isolates from Taiwan, Hong Kong, Malaysia, Australia, and Pacific Islands. Cyproconazole, epoxiconazole, and tebuconazole (Fungicide Resistance Action Committee [FRAC] 3, target-site G1) inhibited colony growth of P. noxius by 99.9 to 100% at 10 ppm and 97.7 to 99.8% at 1 ppm. The other effective fungicide was cyprodinil + fludioxonil (FRAC 9 + 12, target-site D1 + E2), which showed growth inhibition of 96.9% at 10 ppm and 88.6% at 1 ppm. Acropetal translocation of six selected fungicides was evaluated in bishop wood (Bischofia javanica) seedlings by immersion of the root tips in each fungicide at 100 ppm, followed by liquid or gas chromatography tandem mass spectrometry analyses of consecutive segments of root, stem, and leaf tissues at 7 and 21 days posttreatment. Bidirectional translocation of the fungicides was also evaluated by stem injection of fungicide stock solutions. Cyproconazole and tebuconazole were the most readily absorbed by roots and efficiently transported acropetally. Greenhouse experiments suggested that cyproconazole, tebuconazole, and epoxiconazole have a slightly higher potential for controlling BRRD than mepronil, prochloraz, and cyprodinil + fludioxonil. Because all tested fungicides lacked basipetal translocation, soil drenching should be considered instead of trunk injection for their use in BRRD control.
  4. Damayanti TA, Alabi OJ, Rauf A, Naidu RA
    Plant Dis, 2010 Apr;94(4):478.
    PMID: 30754487 DOI: 10.1094/PDIS-94-4-0478B
    Yardlong bean (Vigna unguiculata subsp. sesquipedalis) is extensively cultivated in Indonesia for consumption as a green vegetable. During the 2008 season, a severe outbreak of a virus-like disease occurred in yardlong beans grown in farmers' fields in Bogor, Bekasi, Subang, Indramayu, and Cirebon of West Java, Tanggerang of Banten, and Pekalongan and Muntilan of Central Java. Leaves of infected plants showed severe mosaic to bright yellow mosaic and vein-clearing symptoms, and pods were deformed and also showed mosaic symptoms on the surface. In cv. 777, vein-clearing was observed, resulting in a netting pattern on symptomatic leaves followed by death of the plants as the season advanced. Disease incidence in the Bogor region was approximately 80%, resulting in 100% yield loss. Symptomatic leaf samples from five representative plants tested positive in antigen-coated plate-ELISA with potyvirus group-specific antibodies (AS-573/1; DSMZ, German Resource Center for Biological Material, Braunschweig, Germany) and antibodies to Cucumber mosaic virus (CMV; AS-0929). To confirm these results, viral nucleic acids eluted from FTA classic cards (FTA Classic Card, Whatman International Ltd., Maidstone, UK) were subjected to reverse transcription (RT)-PCR using potyvirus degenerate primers (CIFor: 5'-GGIVVIGTIGGIWSIGGIAARTCIAC-3' and CIRev: 5'-ACICCRTTYTCDATDATRTTIGTIGC-3') (3) and degenerate primers (CMV-1F: 5'-ACCGCGGGTCTTATTATGGT-3' and CMV-1R: 5' ACGGATTCAAACTGGGAGCA-3') specific for CMV subgroup I (1). A single DNA product of approximately 683 base pairs (bp) with the potyvirus-specific primers and a 382-bp fragment with the CMV-specific primers were amplified from ELISA-positive samples. These results indicated the presence of a potyvirus and CMV as mixed infections in all five samples. The amplified fragments specific to potyvirus (four samples) and CMV (three samples) were cloned separately into pCR2.1 (Invitrogen Corp., Carlsbad, CA). Two independent clones per amplicon were sequenced from both orientations. Pairwise comparison of these sequences showed 93 to 100% identity among the cloned amplicons produced using the potyvirus-specific primers (GenBank Accessions Nos. FJ653916, FJ653917, FJ653918, FJ653919, FJ653920, FJ653921, FJ653922, FJ653923, FJ653924, FJ653925, and FJ653926) and 92 to 97% with a corresponding nucleotide sequence of Bean common mosaic virus (BCMV) from Taiwan (No. AY575773) and 88 to 90% with BCMV sequences from China (No. AJ312438) and the United States (No. AY863025). The sequence analysis indicated that BCMV isolates from yardlong bean are more closely related to an isolate from Taiwan than with isolates from China and the United States. The CMV isolates (GenBank No. FJ687054) each were 100% identical and 96% identical with corresponding sequences of CMV subgroup I isolates from Thailand (No. AJ810264) and Malaysia (No. DQ195082). Both BCMV and CMV have been documented in soybean, mungbean, and peanut in East Java of Indonesia (2). Previously, BCMV, but not CMV, was documented on yardlong beans in Guam (4). To our knowledge, this study represents the first confirmed report of CMV in yardlong bean in Indonesia and is further evidence that BCMV is becoming established in Indonesia. References: (1) J. Aramburu et al. J. Phytopathol. 155:513, 2007. (2) S. K. Green et al. Plant Dis. 72:994, 1988. (3) C. Ha et al. Arch. Virol. 153:25, 2008. (4) G. C. Wall et al. Micronesica 29:101, 1996.
  5. Rosli H, Batzer JC, Hernández E, Beruski G, Dixon PM, Gleason ML
    Plant Dis, 2020 Sep;104(9):2398-2405.
    PMID: 32689919 DOI: 10.1094/PDIS-11-19-2340-RE
    The spatial dissemination of three prevalent taxa of sooty blotch and flyspeck (SBFS) fungi under several levels of precipitation was compared during 2015 and 2016 in an Iowa apple orchard. Overhead irrigation was used to supplement ambient precipitation in order to insure SBFS spore dissemination and colony development. There were five irrigation levels, involving 1-min-long periods of irrigation that were imposed either once or twice per hour at intervals of 3, 6, or 12 h, as well as a nonirrigated control. Preselected apple fruit were inoculated with one of the three SBFS taxa to serve as sources of inoculum. Dissemination from these inoculated apple fruit was assessed at harvest by counting SBFS colonies on water-sprayed and nontreated fruit. As a further control, additional fruit were enclosed in fruit bags throughout the fruit development period. In both 2015 and 2016, the number of colonies of the SBFS fungus Peltaster gemmifer per apple increased sharply as the duration of irrigation increased, whereas the number of colonies of Microcyclosporella mali increased to a lesser extent and Stomiopeltis sp. RS1 showed no increase. In 2015, the linear relationship between the duration of irrigation-imposed precipitation levels and the number of colonies on the water-sprayed apple fruit was similar for P. gemmifer (slope = 0.09), Stomiopeltis sp. RS1 (slope = 0.07), and Microcyclosporella mali (slope = 0.13); whereas, in 2016, the slope was higher for P. gemmifer (0.28) than for Stomiopeltis sp. RS1 (-0.09) or M. mali (0.06). The results indicated that dissemination of P. gemmifer increased sharply in response to increased irrigation-imposed precipitation, and that dissemination patterns differed considerably among the three SBFS taxa. The apparent advantage of P. gemmifer in precipitation-triggered dissemination may stem from its ability to produce spores rapidly by budding. To our knowledge, this is the first article to assess splash dispersal by SBFS fungi in the field and the first to document taxon-specific patterns of dissemination in this pathogen complex.
  6. Ismail SI, Batzer JC, Harrington TC, Gleason ML
    Plant Dis, 2016 Feb;100(2):352-359.
    PMID: 30694131 DOI: 10.1094/PDIS-02-15-0137-RE
    Sooty blotch and flyspeck (SBFS) is a fungal disease complex that can cause significant economic losses to apple growers by blemishing the fruit surface with dark-colored colonies. Little is known about the phenology of host infection for this diverse group of epiphytes. In 2009 and 2010, we investigated the timing of infection of apple fruit by SBFS species in six commercial apple orchards in Iowa. Five trees in each orchard received no fungicide sprays after fruit set. Within 3 weeks after fruit set, 60 apples per tree were covered with Japanese fruit bags to minimize inoculum deposition. Subsequently, a subsample of bagged apples was exposed for a single 2-week-long period and then rebagged for the remainder of the growing season. Experimental treatments included seven consecutive 2-week-long exposure periods; control treatments were apples that were either bagged or exposed for the entire season. After apples had been stored at 2°C for 6 weeks following harvest, all SBFS colonies on the apples were identified to species using a PCR-RFLP protocol. A total of 15 species were identified. For the seven most prevalent species, the number of infections per cm2 of fruit surface was greatest on apples that had been exposed early in the season. Two SBFS species, Peltaster fructicola and Colletogloeopsis-like FG2, differed significantly from each other in time required to attain 50% of the total number of colonies per apple, and analysis of variance indicated a significant interaction of SBFS taxon with exposure period. Our findings are the first evidence of species-specific patterns in timing of SBFS inoculum deposition and infection on apple fruit, and strengthen previous observations that most SBFS infections resulting in visible colonies at harvest develop from infections that occur early in the fruit development period. By defining taxon-specific phenological patterns of fruit infection, our findings, when combined with knowledge of region-specific patterns of taxon prevalence, provide a foundation for development of more efficient and cost-effective SBFS management tactics.
  7. Mahmodi F, Kadir JB, Nasehi A, Puteh A, Soleimani N
    Plant Dis, 2013 Nov;97(11):1507.
    PMID: 30708462 DOI: 10.1094/PDIS-03-13-0231-PDN
    At least nine Colletotrichum species, particularly Colletotrichum truncatum, have been recorded on legumes worldwide (1). In June 2010, samples of chickpea leaflets showing leaf spot disease symptoms were collected from experimental farms in Ladang Dua, Selangor state of Malaysia. Tan lesions with darker brown borders were observed on leaflets and were associated with premature leaf drop. Stem lesions initially appeared on the lower parts of stems and later progressed higher in the plant. Lesions often girdled the stem and caused severe dieback. Abundant acervuli developed in the lesions visible as black dots. Foliar lesions were removed, surface sterilized in 1% sodium hypochlorite for 2 min, rinsed twice with distilled water, dried on sterilized tissue paper, plated on PDA plates, and incubated at 25°C (3). Three isolates of the fungus were obtained and identified as C. truncatum on the basis of morphological characteristics (2). The isolates were deposited in the University Putra of Malaysia Culture Collection (UPMCC). Colony characteristics on PDA varied from greyish white to dark in color and exhibited mycelial growth with sparse acervuli. The isolates produced both sclerotia and setae in culture. Conidia (mean ± SD = 22 ± 0.83 × 3.6 ± 0.08 μm, L/W ratio = 6.1) produced in acervuli were falcate, hyaline, and aseptate, with tapering towards the acute and greatly curved apex. The conidial mass color varied from pale buff to saffron. Isolates produced simple to slightly lobed, mainly short clavate appressoria (mean ± SD = 9.60 ± 0.36 × 6.67 ± 0.29 μm, L/W ratio = 1.45). Amplification and sequence analysis of coding and none-coding regions of the ITS-rDNA (GenBank Accession JX971160), actin (JX975392), β-tubulin (KC109495), histone (KC109535), chitin synthase (KC109575), and glyceraldehyde-3-phosphate dehydrogenase (KC109615) obtained from the representative isolate, CTM37, aligned with deposited sequences from GenBank and revealed 99 to 100% sequence identity with C. truncatum strains (AJ301945, KC110827, GQ849442, GU228081, GU228359, and HM131501 from GenBank). Isolate CTM37 was used to test pathogenicity in the greenhouse. Five chickpea seeds of cultivar ILC-1929 were sown per pot in four replications. Ten days after seedling emergence, plants were inoculated with a spore suspension (concentration = 106 conidia ml-1) and check pots were sprayed with distilled water. After inoculation, the plants were covered with plastic bags for 48 h and kept at 28 to 33°C and >90% RH. After incubation, the plastic bags were removed and the plants were placed on greenhouse benches and monitored daily for symptom development (3). One week after inoculation, typical anthracnose symptoms developed on the leaves and stems of inoculated plants including acervuli formation, but not on the checks. A fungus with the same colony and conidial morphology as CTM37 was recovered from the lesions on the inoculated plants. The experiment was repeated twice. The ability to accurately diagnose Colletotrichum species is vital for the implementation of effective disease control and quarantine measures. We believe this is the first report of C. truncatum causing anthracnose on chickpea in Malaysia. References: (1) B. D. Gossen et al. Can. J. Plant Pathol. 31:65, 2009. (2) B. C. Sutton. The Genus Glomerella and its anamorph Colletotrichum. CAB International, Wallingford. UK. 1992. (3) P. P. Than et al. Plant Pathol. 57:562, 2008. ERRATUM: A correction was made to this Disease Note on May 19, 2014. The author N. Soleimani was added.
  8. Tsai WS, Shih SL, Green SK, Jan FJ
    Plant Dis, 2007 Jul;91(7):907.
    PMID: 30780410 DOI: 10.1094/PDIS-91-7-0907A
    Whitefly-transmitted, cucurbit-infecting begomoviruses (genus Begomovirus, family Geminiviridae) have been detected on cucurbit crops in Bangladesh, China, Egypt, Israel, Malaysia, Mexico, the Philippines, Thailand, United States, and Vietnam. Pumpkin plants showing leaf curling, blistering, and yellowing symptoms were observed in the AVRDC fields (Tainan, Taiwan) during 2001 and in nearby farmers' fields during 2005. Two samples from symptomatic plants were collected in 2001 and six collected in 2005. Viral DNAs were extracted (2), and the PCR, with previously described primers, was used to detect the presence of begomoviral DNA-A (4), DNA-B (3), and associated satellite DNA (1). Begomoviral DNA-A was detected in one of the 2001 samples and in all 2005 samples. The PCR-amplified 1.5 kb viral DNA-A from one positive sample each from the 2001 and 2005 collections was cloned and sequenced. On the basis of the 1.5-kb DNA-A sequences, specific primers were designed to completely sequence the DNA-A component. The overlap between fragments obtained using primer walking ranged from 43 to 119 bp with 100% nt identities. The complete DNA-A sequences were determined for the two isolates as 2,734 bp (2001) (GenBank Accession No. DQ866135) and 2,733 bp (2005) (GenBank Accession No. EF199774). Sequence comparisons and analyses were performed using the DNAMAN Sequence Analysis Software (Lynnon Corporation, Vaudreuil, Quebec, Canada). The DNA-A of the begomovirus isolates each contained the conserved nanosequence-TAATATTAC and six open reading frames, including two in the virus sense and four in the complementary sense. On the basis of a 99% shared nucleotide sequence identity, they are considered isolates of the same species. BLASTn analysis and a comparison of the sequence with others available in the GenBank database ( http://www.ncbi.nlm.nih.gov ) indicated that the Taiwan virus shared its highest nt identity (more than 95%) with the Squash leaf curl Philippines virus (GenBank Accession No. AB085793). Virus-associated satellite DNA was not found in any of the samples. DNA-B was found in both samples, providing further evidence that the virus was the same as the bipartite Squash leaf curl Philippines virus. To our knowledge, this is the first report of Squash leaf curl Philippines virus in Taiwan. References: (1) R. W. Briddon et al. Virology 312:106, 2003. (2) R. L. Gilbertson et al. J. Gen. Virol. 72:2843, 1991. (3) S. K. Green et al. Plant Dis. 85:1286, 2001. (4) M. R. Rojas et al. Plant Dis. 77:340, 1993.
  9. Márquez-Licona G, García-León E, Flores-Moctezuma HE, Solano-Báez AR
    Plant Dis, 2023 Sep 27.
    PMID: 37755414 DOI: 10.1094/PDIS-04-23-0797-PDN
    Frangipani (Plumeria rubra L.; Apocynaceae.) is a deciduous ornamental shrub, native to tropical America and widely distributed in tropical and subtropical regions. In Mexico, P. rubra is also used in traditional medicine and religious ceremonies. In November 2018-2022, rust-diseased leaves of P. rubra were found in Yautepec (18°49'29"N; 99°05'46"W), Morelos, Mexico. Symptoms of the disease included small chlorotic spots on the adaxial surface of the infected leaves, which as the disease progressed turned into necrotic areas surrounded by a chlorotic halo. The chlorotic spots observed on the adaxial leaf surface coincided with numerous erumpent uredinia of bright orange color on the abaxial leaf surface. As a result of the infection, foliar necrosis and leaves abscission was observed. Of the 40 sampled trees, 95% showed symptoms of the disease. On microscopic examination of the fungus, bright orange, subepidermal uredinia were observed, which subsequently faded to white. Urediniospores were bright yellow-orange color. They were ellipsoid or globose, sometimes angular, echinulate, (21.5) 26.5 (33.0) × (16.0) 19.0 (23.0) μm in size. Morphological features of the fungus correspond with previous descriptions of Coleosporium plumeriae by Holcomb and Aime (2010) and Soares et al., (2019). A voucher specimen was deposited in the Herbarium of the Departmet of Plant-Insect Interactions at the Biotic Products Development Center of the National Polytechnic Institute under accession no. IPN 10.0113. Species identity was confirmed by amplifying the 5.8S subunit, the ITS 2 region, and part of the 28S region with rust-specific primer Rust2inv (Aime, 2006) and LR6 (Vilgalys and Hester 1990). The sequence was deposited in GenBank (OQ518406) and showed 100% sequence homology (1435/1477bp) with a reference sequence (MG907225) of C. plumeriae from Plumeria spp. (Aime et al. 2018). Pathogenicity was confirmed by spraying a urediniospores suspension of 2×104 spores ml-1 onto ten plants of P. rubra. Six plants were inoculated and sealed in plastic bags, while four noninoculated plants were applied with sterile distilled water. Plants were inoculated at 25°C and held for 48 h in a dew chamber, after this, the plants were transferred to greenhouse conditions (33/span>2°C). The experiment was performed twice. All inoculated plants developed rust symptoms after 14 days, whereas the non-inoculated plants remained symptomless. The recovered fungus was morphologically identical to that observed in the original diseased plants, thus fulfilling Koch's postulates. According to international databases (Crous 2004; Farr and Rossman 2023), C. plumeriae has not been officially reported in Mexico, despite being a prevalent disease. Diseased plants have been collected and deposited in herbaria, unfortunately, these reports lack important information such as geographic location of sampling, pathogenicity tests, or molecular evidence, which are essential for a comprehensive study of the disease in Mexico. To our knowledge, this is the molecular confirmation of Coleosporium plumeriae causing rust of Plumeria rubra in Mexico. Rust of P. rubra caused by C. plumeriae has been previously identified in India, Taiwan, Malaysia, and Indonesia by Baiswar et al. (2008), Chung et al. (2006), Holcomb and Aime (2010) and Soares et al., (2019). This disease causes important economic losses in nurseries, due to the defoliation of infected plants.
  10. Green SK, Tsai WS, Shih SL, Black LL, Rezaian A, Rashid MH, et al.
    Plant Dis, 2001 Dec;85(12):1286.
    PMID: 30831796 DOI: 10.1094/PDIS.2001.85.12.1286A
    Production of tomato (Lycopersicon esculentum) in Bangladesh, Malaysia, Myanmar, Vietnam, and Laos has been severely affected by yellow leaf curl disease. Tomato leaf samples were collected from symptomatic tomato plants from farmers' fields in the five countries from 1997 to 1999. DNA was extracted from all samples, four from Vietnam, two each from Malaysia, Laos, and Myanmar, and seven from Bangladesh. Virus DNA was amplified by polymerase chain reaction (PCR) using the begomovirus-specific degenerate primer pair PAL1v 1978/PAR1c 715(1), which amplifies the top part of DNA A. All samples gave the expected 1.4-kb PCR product. The PCR product of one sample per country was cloned and sequenced. Based on the sequences of the 1.4-kb DNA products amplified by the first primer pair, specific primers were designed to complete each of the DNA A sequences. Computer-assisted sequence comparisons were performed with begomovirus sequences available in the laboratory at the Asian Vegetable Research and Development Center, Shanhua, Tainan, and in the GenBank sequence database. The five DNA species resembled DNA A of begomoviruses. For the detection of DNA B two degenerate primer pairs were used, DNABLC1/DNABLV2 and DNABLC2/DNABLV2 (DNABLC1: 5'-GTVAATGGRGTDCACTTCTG-3', DNABLC2: 5'-RGTDCACTT CTGYARGATGC-3', DNABLV2: 5'-GAGTAGTAGTGBAKGTTGCA-3'), which were specifically designed to amplify DNA B of Asian tomato geminiviruses. Only the virus associated with yellow leaf curl of tomato in Bangladesh was found to contain a DNA B component, which was detected with the DNABLC1/DNABLV2 primer pair. The DNA A sequence derived from the virus associated with tomato yellow leaf curl from Myanmar (GenBank Accession No. AF206674) showed highest sequence identity (94%) with tomato yellow leaf curl virus from Thailand (GenBank Accession No. X63015), suggesting that it is a closely related strain of this virus. The other four viruses were distinct begomoviruses, because their sequences shared less than 90% identity with known begomoviruses of tomato or other crops. The sequence derived from the virus associated with tomato yellow leaf curl from Vietnam (GenBank Accession No. AF264063) showed highest sequence identity (82%) with the virus associated with chili leaf curl from Malaysia (GenBank Accession No. AF414287), whereas the virus associated with yellow leaf curl symptoms in tomato in Bangladesh (GenBank Accession No. AF188481) had the highest sequence identity (88%) with a tobacco geminivirus from Yunnan, China (GenBank Accession No. AF240675). The sequence derived from the virus associated with tomato yellow leaf curl from Laos (GenBank Accession No. AF195782) had the highest sequence identity (88%) with the tomato begomovirus from Malaysia (GenBank Accession No. AF327436). This report provides further evidence of the great genetic diversity of tomato-infecting begomoviruses in Asia. Reference: M. R. Rojas et al. Plant Dis. 77:340, 1993.
  11. Nasehi A, Kadir JB, Esfahani MN, Mahmodi F, Ghadirian H, Ashtiani FA, et al.
    Plant Dis, 2013 May;97(5):689.
    PMID: 30722190 DOI: 10.1094/PDIS-10-12-0902-PDN
    In June 2011, lettuce (Lactuca sativa) plants cultivated in major lettuce growing areas in Malaysia, including the Pahang and Johor states, had extensive leaf spots. In severe cases, disease incidence was recorded more than 80%. Symptoms on 50 observed plants initially were as water soaked spots (1 to 2 mm in diameter) on leaves, and then became circular spots spreading over much of the leaves. In this research, main lettuce growing areas infected by the pathogen in the mentioned states were investigated and the pathogen was isolated onto potato dextrose agar (PDA). Colonies observed were greyish green to light brown. Single conidia were formed at the terminal end of conidiophores that were 28.8 to 40.8 μm long and 11.0 to 19.2 μm wide, and 2 to 7 transverse and 1 to 4 longitudinal septa. To produce conidia, the fungus was grown on potato carrot agar (PCA) and V8 juice agar media under 8-h/16-h light/dark photoperiod. Fourteen isolates were identified Stemphylium solani based on morphological criteria described by Kim et al. (1). To confirm morphological characterization, DNA of the fungus was extracted from mycelium and PCR was done using universal primers ITS5 (5'-GGAAGTAAAAGTCGTAACAAGG-3') and ITS4 (5'-TCCTCCGCTTATTGATATGC-3'), which amplified the internal transcribed spacer (ITS) region of rDNA (2). The sequencing result was subjected to BLAST analysis which was 99% identical to the other published sequences in the GenBank database (GenBank Accession Nos. AF203451 and HQ840713). The nucleotide sequence was deposited in GenBank under Accession No. JQ736022. Pathogenicity testing of representative isolate was done using 20 μl of conidial suspension with a concentration of 1 × 105/ml in droplets (three drops on each leaf) on four detached 45-day-old lettuce leaves cv. BBS012 (3). Fully expended leaves were placed on moist filter paper in petri dishes and were incubated in humid chambers at 25°C. The leaves inoculated with sterile water served as control. After 7 days, disease symptoms were observed, which were similar to those symptoms collected in infected fields and the fungus was reisolated and confirmed as S. solani based on morphological criteria (1) and molecular characterization (2). Control leaves remained healthy. Pathogenicity testing was completed twice. To our knowledge, this is the first report of S. solani on lettuce in Malaysia and it may become a serious problem because of its broad host range, variability in pathogenic isolates, and prolonged active phase of the disease cycle. Previous research has shown that S. solani is a causal agent of gray leaf spot on lettuce in China (4). References: (1) B. S. Kim et al. Plant Pathol. J. 20:85, 2004. (2) Y. R. Mehta et al. Current Microbiol. 44:323, 2002. (3) B. M. Pryor and T. J. Michailides. Phytopathology 92:406, 2002. (4) F. L. Tai. Sylloge Fungorum Sinicorum, Sci. Press, Acad. Sin., Peking, 1979.
  12. Ray JD, Subandiyah S, Rincon-Florez VA, Prakoso AB, Mudita IW, Carvalhais LC, et al.
    Plant Dis, 2021 Oct;105(10):2792-2800.
    PMID: 33973808 DOI: 10.1094/PDIS-01-21-0149-RE
    Blood disease in bananas caused by Ralstonia syzygii subsp. celebesensis is a bacterial wilt causing significant crop losses in Indonesia and Malaysia. Disease symptoms include wilting of the plant and red-brown vascular staining, internal rot, and discoloration of green banana fruit. There is no known varietal resistance to this disease in the Musa genus, although variation in susceptibility has been observed, with the popular Indonesian cooking banana variety Kepok being highly susceptible. This study established the current geographic distribution of Blood disease in Indonesia and confirmed the pathogenicity of isolates by Koch's postulates. The long-distance distribution of the disease followed an arbitrary pattern indicative of human-assisted movement of infected banana materials. In contrast, local or short-distance spread radiated from a single infection source, indicative of dispersal by insects and possibly contaminated tools, water, or soil. The rapid expansion of its geographical range makes Blood disease an emerging threat to banana production in Southeast Asia and beyond.
  13. Balmas V, Corda P, Marcello A, Bottalico A
    Plant Dis, 2000 Jul;84(7):807.
    PMID: 30832117 DOI: 10.1094/PDIS.2000.84.7.807B
    Fusarium nygamai Burgess & Trimboli was first described in 1986 in Australia (1) and subsequently reported in Africa, China, Malaysia, Thailand, Puerto Rico, and the United States. F. nygamai has been reported on sorghum, millet, bean, cotton, and in soil where it exists as a colonizer of living plants or plant debris. F. nygamai was also reported as a pathogen of the witch-weed Striga hermonthica (Del.) Benth. To our knowledge, no reports are available on its pathogenicity on crops of economic importance. In a survey of species of Fusarium causing seedling blight and foot rot of rice (Oryza sativa L.) carried out in Sardinia (Oristano, S. Lucia), F. nygamai was isolated in association with other Fusarium species-F. moniliforme, F. proliferatum, F. oxysporum, F. solani, F. compactum, and F. equiseti. Infected seedlings exhibited a reddish brown cortical discoloration, which was more intense in older plants. The identification of F. nygamai was based on monoconidial cultures grown on carnation leaf-piece agar (CLA) (2). The shape of macroconidia, the formation of microconidia in short chains and false heads, and the presence of chlamydospores were used as the criteria for identification. Two pathogenicity tests comparing one isolate of F. nygamai with one isolate of F. moniliforme were conducted on rice cv. Arborio sown in artificially infested soil in a greenhouse at 22 to 25°C. The inoculum was prepared by growing both Fusarium species in cornmeal sand (1:30 wt/wt) at 25°C for 3 weeks. This inoculum was added to soil at 20 g per 500 ml of soil. Pre- and post-emergence damping-off was assessed. Both F. nygamai and F. moniliforme reduced the emergence of seedlings (33 to 59% and 25 to 50%, respectively, compared to uninoculated control). After 25 days, the seedlings in infested soil exhibited a browning of the basal leaf sheaths, which progressed to a leaf and stem necrosis. Foot rot symptoms caused by F. nygamai and F. moniliforme were similar, but seedlings infected by F. nygamai exhibited a more intense browning on the stem base and a significant reduction of plant height at the end of the experiment. Either F. nygamai or F. moniliforme were consistently isolated from symptomatic tissue from the respective treatments. References: (1) L. W. Burgess and D. Trimboli. Mycologia 78:223,1986. (2) N. L. Fisher et al. Phytopathology 72:151,1982.
  14. Qin R, Li Q, Huang S, Chen X, Mo J, Guo T, et al.
    Plant Dis, 2023 Mar 27.
    PMID: 36973906 DOI: 10.1094/PDIS-05-22-1168-PDN
    Persimmon (Diospyros kaki Thunb.) is widely cultivated in China. On October 15, 2019, about 10% of persimmon fruits showed fruit rot in the orchards of Guilin, Guangxi, China (24°45' N, 110°24' E), which could cause more than 15% of yield losses. The initial symptoms of fruit rot exhibited irregular brown to black spots (range from 2 to 4 cm in diameter), the areas surrounding the blackened spots would be soft and rotten, and three diseased fruit samples were collected from three orchards, respectively. Tissues (5×5 mm) were cut from infected margins, surface-disinfected in 75% ethanol for 10 s, 2% NaClO for 2 min, rinsed three times in sterilized distilled water, and incubated on potato dextrose agar (PDA) at 25°C under 12/12 h light/darkness for a week. Forty-one tissues yielded morphologically similar cultures, and three representative isolates LPG1-1, LPG1-2, and YSG-1 were selected from three samples for further study, respectively. Their colonies showed wavy edges, white surfaces, and dense aerial hyphae on PDA after two weeks. Conidia were fusiform, straight to slightly curved, and 4-septate; basal cells were conical, hyaline, thin, and verruculose with two or three long and hyaline apical appendages and one short apical appendage; three median cells of LPG1-1 with length 14.06 to 17.69 μm (n=100), and LPG1-2 with length 14.03 to 17.61 μm (n=100) were dark brown to olivaceous, while three median cells of YSG-1 with length 12.54 to 15.58 μm (n=100) were dark brown. The conidial sizes of LPG1-1, LPG1-2, and YSG-1 were 17.41 to 27.68 × 4.63 to 8.55 μm (n=100), 18.06 to 27.41 × 4.33 to 8.21 μm (n=100), and 16.58 to 27.73 × 4.99 to 8.39 μm (n=100), respectively. The morphological characteristics were consistent with Neopestalotiopsis spp. (Maharachchikumbura et al. 2012; Maharachchikumbura et al. 2014). Primer pairs ITS4/ITS5, BT2a/BT2b, and EF1-526F/EF-1567R were used to amplify internal transcribed spacer (ITS), beta-tubulin (TUB2), and translation elongation factor 1 alpha (TEF1-α), respectively (Shu et al., 2020). All DNA fragments were sequenced by Sangon Biotech Co., Ltd. (Shanghai, China). Sequences have been deposited in GenBank (ITS: OM349120 to OM349122, TUB2: OM688188 to OM688190, TEF1-α: OM688191 to OM688193). Based on BLASTn analysis of ITS, TUB2, and TEF1-α sequences, the LPG1-1 and LPG1-2 showed over 99% similarity to N. saprophytica, and YSG-1 showed over 99% similarity to N. ellipsospora. Phylogenetic analysis of the three isolates was performed with MEGA10 (version 10.0) based on sequences of ITS, TUB2, and TEF1-α using maximum parsimony analysis. The results revealed that LPG1-1 and LPG1-2 were clustered with N. saprophytica, and YSG-1 was clustered with N. ellipsospora. Pathogenicity tests of three isolates were conducted on 72 healthy persimmon fruits with and without wounds, and 9 fruits are for each treatment. The wound was made by a sterilized needle. Fruits were pre-processed with 75% ethanol for 10 s, 1% NaClO for 2 min and rinsed three times in sterile water. Conidial suspensions (10 µL, 106 conidia/mL in 0.1% sterile Tween 20) were inoculated on each site (4 sites/fruit). Control group was treated with 0.1% sterile Tween 20. All inoculated sites were covered with wet cotton. The inoculated fruits were placed in a plastic box to maintain humidity at 28℃. After 5 days, all wounded fruits showed fruit rot, whereas unwounded and control fruits remained asymptomatic, there were significant differences (P<0.05) in aggressiveness between N. saprophytica (average lesion diameter 13.1 mm) and N. ellipsospora (average lesion diameter 14.9 mm). Koch's postulates were fulfilled by re-isolating the causal agents from inoculated fruits. N. ellipsospora was previously reported as an endophyte in D. montana in southern India (Reddy et al. 2016). N. saprophytica could cause leaf spot of Erythropalum scandens and Magnolia sp., and fruit rot of Litsea rotundifolia in China and leaf spot of Elaeis guineensis in Malaysia (Yang et al. 2021, Ismail et al. 2017). To our knowledge, this is the first report of N. ellipsospora and N. saprophytica causing fruit rot on persimmon in the world. The results will provide a foundation for controlling fruit rot caused by pestalotioid fungi on persimmon.
  15. Inokuti EM, Saraiva JLR, Silva DEMD, Corrêa MCM, Lima CS
    Plant Dis, 2023 Oct 26.
    PMID: 37884480 DOI: 10.1094/PDIS-09-23-1985-PDN
    In November 2021, stem gray blight symptoms were seen on two dragon fruit (pitaya) species (Hylocereus megalanthus and H. polyrhizus) in an orchard with 100% disease incidence in Fortaleza, Ceará, Brazil (3°44'24.5"S 38°34'30.8"W). The symptoms were initially yellowish to dark brown lesions, and as the symptoms progressed, the lesions turned grayish with small black pycnidia in the center. Isolation was carried out by disinfecting small pieces of the symptomatic stems in 70% ethanol for 1 min, followed by 1% NaOCl for 1 min, and then rinsed three times with sterile distilled water. Excess water was removed using sterile filter paper. Then the stem fragments were placed on PDA media. Colonies produced small black pycnidia with conidia and some were sterile after 68 days of incubation. Two monosporic isolates were obtained from the colonies: UFCM 0708 from H. megalanthus and the UFCM 0710 from H. polyrhizus, which were used for pathogenicity test, morphological and molecular identification. The colony on PDA was smoke gray with aerial mycelium and the reverse was smoke grey to dark grey. The α-conidia from UFCM 0708 and UFCM 0710 were hyaline, aseptate and fusiform and measured 6.4 to 9.7 (8.0) x 1.2 to 2.4 (1.7) µm and 6 to 13.1 (8.2) x 1.7 to 2.4 (2.0) µm, respectively. The β-conidia from UFCM 0708 and UFCM 0710 were hyaline, aseptate and filiform and measured 15 to 22.5 (18.8) x 0.6 to 1.7 (1.0) µm, and 17.2 to 27.5 (22.3) x 0.5 to 1.0 (0.8) µm (n=30), respectively. This morphology placed the isolates as Diaporthe sp. (Udayanga et al. 2012). For further confirmation, genomic DNA was extracted from the isolates (UFCM 0708 and UFCM 0710), and beta-tubulin (TUB2) and translation elongation factor 1-alpha (TEF1) gene fragments were amplified. BLASTn search results with isolates TEF1 and TUB2 sequences varied from 98.58% to 99.52% identity to the ex-type sequence of Diaporthe arecae (CBS 161.64). Phylogenetic analysis of concatenated sequences alignment carried out using the Maxinum-likelihood and Bayesian Inference analysis placed the isolates within D. arecae clade with 86% bootstrap and 0.99 posterior probabilities support. The sequences obtained in this study were deposited in GenBank (TEF1: OP534720 and OP534722; TUB2: OP534717 and OP534719). The isolates were confirmed as D. arecae based on molecular analysis and morphological characteristics (Gomes et al. 2013). Koch's postulates were completed as described by Karim et al. (2019) through the inoculation of six stems of each dragon fruit (pitaya) species. The stems were wounded by removing a 5 mm diameter disc and after that they were inoculated with a 5 mm diameter mycelial plug from 5 days old PDA plates. PDA plugs were used as control. Each stem was covered with a plastic bag and sterilized water was added into the sterilized filter paper to maintain humidity. The bags were kept in a room at day and night temperature of 25 ± 2 °C. The same symptoms seen in the field appeared on the stems 21 days after inoculation. The control stems remained symptomless. Diaporthe arecae have been reported on H. polyrhizus in Malaysia (Huda-Shakirah et al. 2021). To our knowledge, this is the first report of D. arecae on H. megalanthus and H. polyrhizus in Brazil.
  16. Kuruppu M, Siddiqui Y, Ahmad K, Ali A
    Plant Dis, 2020 Dec 29.
    PMID: 33373283 DOI: 10.1094/PDIS-10-20-2318-PDN
    Repeated sampling conducted from December 2019 to March 2020, and fruit of pineapple (Ananas comosus) var MD2 showing early stem end rot symptoms including brown and rotten fruit skin near the stem end region (Fig.1Aa) or darker skin with black discoloration (Fig.1Ab) indicated a consistent fungal infection. The samples (30 fruits from each location) were collected from store houses in three farmer fields with 60% disease incidence in Serdang, (3.0220oN,101.7055oE), Selangor, West Malaysia. The pulp of infected fruits appeared watery with characteristic spoilage odour. Symptomatic necrotic tissues from stem end region and skin were cut in to pieces (1x1cm), surface sterilized and plated onto potato dextrose agar amended aseptically with 0.5 g L-1 streptomycin sulphate. The plates were incubated at room temperature (28±2oC) in natural light conditions. Five days old cultures were light grey in colour and gradually turned dark brown to black with dense deeply tufted, mycelium as the culture aged (Fig.1B, C). Conidial morphology was observed using compound microscope (Olympus model BX-50F4, Tokyo, Japan) equipped with Dino-Eye. Branched mycelia with 0-1 septate arthospores were evident in 14 days old cultures (Fig.1D). Measured arthroconidia (5 to10x3 to 4.5µm) were ellipsoid to ovoid or round shaped, hyaline with an acutely rounded apex, truncate base, initially aseptate (Fig.1E) and arranged as chain at maturity (Fig.1F). The pathogen was identified through PCR amplification of the internal transcribed spacer (ITS) region using ITS1 and ITS4 primers (White et al., 1990) and BLASTn homology search as Neoscytalidium dimidiatum based on 100% similarity to a reference sequence (accession number KJ648577) that was previously deposited (Mohd et al.,2013). The sequence was deposited in Gen Bank ( accession number MW082810). Pathogenicity test was performed using the mycelial plug inoculation method and repeated twice with five replicates. Healthy MD2 pineapple fruits were surface sterilized with 1% NaOCl solution for15 min. followed by washing with sterilized distilled water. One centimeter diameter PDA plug at the margin of actively growing seven days old cultures were inserted in each of two inoculation wounds made on the skin and stem end of each fruit then the wounds were wrapped with moist cotton wool. Non-colonized PDA plugs were used to inoculate the control fruits. Fruits were incubated under 85% RH at room temperature. Five days after inoculation, the fruits showed similar dark necrotic discoloration and confirmed as N.dimidiatum by PCR (Fig.1G). The Koch postulates were fulfilled by inoculation and re-isolation of the fungal pathogen. This pathogen has also been reported previously to cause economic losses on a number of other hosts, such as pitayah fruits in Israel and Malaysia (Erza et al., 2013; Mohd et al., 2013)) and almond in California (Mohomed et al., 2018). To our knowledge this is the first report of N. dimidiatum causing postharvest stem end rot on MD2 pineapple in Malaysia. It may have the possibility to develop postharvest economic losses to pineapple industry, if severely affected fruits with high population of the pathogen left unattended in store houses.
  17. Wang YC, Liu JH, Huang CC, Hong CF
    Plant Dis, 2021 Nov 09.
    PMID: 34752123 DOI: 10.1094/PDIS-09-21-1902-PDN
    Dragon fruit (Hylocereus polyrhizus & H. undatus) is a rapidly growing commodity in Taiwan. The production acreage has been tripled since 2011, with an estimation of over 2,800 ha in 2019. From disease survey conducted in July 2020, reddish orange to blackish brown lesions similar to stem canker caused by Neoscytalidium dimidiatum on dragon fruit cladodes (Supplementary Fig. S1, Q) were observed from two orchards in Central Taiwan. Diseased cladodes were brought back to the lab, surface disinfested with 70% ethanol for 15 to 30 sec, and then blotted dried with a paper towel. Small pieces (about 3x3 mm) of necrotic spots were excised, placed on 2% water agar (WA) plates, and incubated with 12 h photoperiod at 28 ± 2 ℃ for 3 days. Among the necrotic spots that were used for fungal isolation, some were detected to have N. dimidiatum accounting for 21 isolates, while three isolates detected in other spots were unknown. Single hyphal tips of the three unknown fungal colonies with similar morphology were transferred on potato dextrose agar (PDA). Brownish- to grayish-white colonies with fluffy aerial mycelium were observed on PDA (Supplementary Fig. S1, A, B, E, F, I and J) after 8 days of incubation. To induce the sporulation, all the fungal isolates were cultivated on autoclaved cowpea pods on 2% WA plates with 12 h photoperiod at 25 ± 2 ℃ for 3 weeks. Black pycnidia embedded in cowpea tissues and creamy yellowish exudates with pycnidiospores extruding from the ostiole were observed (Supplementary Fig. S1, C, G and K). Alpha-conidia were characterized as aseptate, hyaline, smooth, ellipsoidal or fusiform, often bi-guttulate and measured about 6.0 to 6.5 μm × 2.0 to 2.3 μm (n = 50 for each isolate) (Supplementary Fig. S1, D, H and L). Beta-conidia were not observed. Morphological characteristics of these isolates were similar to Diaporthe spp. described by Udayanga et al. (2015). To further identify the fungal isolates, the internal transcribed spacer (ITS), β-tubulin (TUB) and translation elongation factor 1-α (EF1-α) regions were amplified using primer pairs ITS1/ITS4 (White et al. 1990), Bt2a/Bt2b (Glass & Donaldson 1995) and EF1-728F/EF1-986R (Carbone & Kohn 1999), respectively. BLAST analysis of isolates CH0720-010 (ITS: OK067377; TUB: OK149767; EF1-α: OK149764), CH0720-013 (ITS: OK067378; TUB: OK149768; EF1-α: OK149765) and TC0720-016 (ITS: OK067379; TUB: OK149769; EF1-α: OK149766) showed 99.78 to 100% of ITS identity, 98.8 to 99.2% of TUB identity, and 100% of EF1-α identity with Diaporthe ueckerae (ITS: KY565426; TUB: KY569384; EF1-α: KY569388). Phylogenetic trees were constructed using concatenated ITS, TUB, and EF1-α sequences based on maximum likelihood with HKY+G model, maximum parsimony, and Bayesian inference method in MEGA X and Geneious Prime 2020.2.4. All isolates were clustered in D. ueckerae with similar topology based on aforementioned methods, hence the phylogram of maximum likelihood was presented (Supplementary Fig. S2). To confirm the pathogenicity, detached dragon fruit (H. polyrhizus and H. undatus) cladodes (20 to 30 cm in length) were surface disinfested, wounded with sterilized syringe (about 2 mm in depth), and inoculated with mycelial plugs (6 mm in diam.) from 5-day-old colonies on PDA. Each isolate had three mycelial plugs and the PDA plugs without mycelium were inoculated as negative control. Inoculated cladodes were placed in a moisture chamber and incubated at 30 ± 2 ℃ with 12 h photoperiod. Two days after inoculation (DAI), the agar plugs were removed and symptom development on the cladodes was photo recorded every other day. The inoculation experiment was repeated twice. At 6 DAI, round to irregular, dark-brown, and water-soaking lesions were observed on the cladodes of both species inoculated with the three D. ueckerae isolates whereas all negative controls remained asymptomatic (Supplementary Fig. S1, M-P). Morphologically identical fungi were re-isolated from inoculated cladodes, fulfilling Koch's postulates. Several Diaporthe species have been reported infecting dragon fruit in the southeastern Asian countries such as Thailand, Bangladesh and Malaysia (Udayanga et al. 2012; Karim et al. 2019; Huda-Shakirah et al. 2021). To our knowledge, this is the first report of stem rot caused by D. ueckerae in Taiwan. Since the field symptoms may be easily confused with those caused by N. dimidiatum, the potential threat of Diaporthe species complex on dragon fruit should be aware and may warrant further study.
  18. Luo Z, Liu P, Qi H, Chen X, Zhang J, Sun C, et al.
    Plant Dis, 2023 Nov 30.
    PMID: 38035784 DOI: 10.1094/PDIS-03-23-0580-PDN
    Styphnolobium japonicum (L.) Schott (family Fabaceae Juss.) also called pagoda tree, is widely planted in northern China in landscape plantings, for erosion control and forestry. In recent years, symptoms of branch dieback were observed on S. japonicum in the southern part of Xinjiang province, China. From 2019 to 2022, in total ca. 1000 ha area was surveyed in Korla (41.68°N, 86.06°E), Bohu (41.95°N, 86.53°E) and Alaer (41.15°N, 80.29°E). Typical symptoms were observed in 70% of the surveyed branches. To identify the cause, we collected 50 symptomatic branches. Symptoms were initially observed on green current-year twigs, which turned grayish white in color. In the later stages of disease development, a large number of nacked black conidia formed under epidermis of perennial branches, causing visible black protrusions (pycnidia) on branch surface. The disease occurred throughout the entire growing season of S. japonicum. Symptoms also occurred on the inflorescence, fruit, and twigs. In some cases, infection resulted in tree mortality. Isolations were made from the margin between healthy and diseased tissues. Small pieces were excised, surface disinfested (75% ethanol 30 s, 1% NaClO solution 5 mins), cut into pieces (5 to 10 mm2), and incubated on PDA medium at 28℃ for 3 days. A total of 16 isolates (GH01-GH16) with similar colony morphology were obtained. The colonies were initially white, gradually turning to olive-green on the surface and black on the underside after 7 days. Microscopically, the conidia were aseptate, 1-septate, two-septate, and muriform, 2.6-4.5 × 2.9-27.6 μm (n=50). Pycnidia ranged in size from 120.2 to 135.5 × 112.4 to 118.6 µm (n=20). Those morphological characters matched the descriptions of Neoscytalidium dimidiatum (previously N. novaehollandiae) (Alizadeh et al. 2022; Pavlic et al. 2008). For molecular identification, genomic DNA of GH01-GH16 were extracted from fresh mycelia. The internal transcribed spacer (ITS), large subunit ribosomal RNA gene (LSU), and translation elongation factor 1-alpha (EF1-α) gene were amplified using the primer sets ITS1/ITS4 (White 1990), LRoR/LR5 (Vilgalys and Hester 1990) and EF1-728F/EF1-986R (Carbone and Kohn 1999). The sequences were deposited in GenBank (accession No. OP379832, OQ096643-OQ096657 for ITS, OP389048, OQ127403-OQ127417 for LSU, and OQ136617, OQ586044-OQ586058 for EF1-α). The ITS sequence had 100% identity (505/505 bp) to MT362600. Similarly, the LSU and EF1-α sequences were found to be identical to MW883823 (100%, 821/821 bp) and KX464763(99%, 256/258 bp), respectively. Pathogenicity was tested on one-year-old healthy S. japonicum seedlings. Spores of representative isolate GH01 were produced on PDA by incubating for 7-days at 28℃. Conidia were washed with sterile water. Five trees were inoculated with 1 × 106 conidia/ml conidial suspensions and five trees were sprayed with sterile water. All trees were covered with plastic bags for 24 h and kept at 25°C in a greenhouse. Signs and symptoms were similar to those observed in field collections one month after inoculation, while no symptoms occurred on the controls. The original fungus was successfully reisolated from the inoculated trees and was identified as N. dimidiatum following the methods described above. N. dimidiatum has been reported in many Asian country such as Malaysia, India, Turkey, and Iran(Akgül et al. 2019; Alizadeh et al. 2022; Khoo et al. 2023; Salunkhe et al. 2023). To our knowledge, this is the first report of N. dimidiatum associated with branch dieback of S. japonicum in China. Our findings have expanded the host range of N. dimidiatum in China and provides a theoretical basis for the diagnosis and treatment of the disease.
  19. Mahmud NU, Chakraborty M, Paul SK, Gupta DR, Surovy MZ, Rahman M, et al.
    Plant Dis, 2020 Aug 04.
    PMID: 32748716 DOI: 10.1094/PDIS-01-20-0005-PDN
    Dragon fruit (Hylocereus polyrhizus) is a high value newly introduced fruit crop in Bangladesh. It has drawn considerable public attention due to its appealing flesh color, sweet taste and fruit qualities. Recently, basal rot of dragon fruit plants was observed in several farmer's fields, nurseries and in the research field of Bangabandhu Sheikh Mujibur Rahman Agricultural University (BSMRAU) where about 10-15% of plants were infected in each location. Initially, the symptoms appeared in the basal part near the soil as brown lesions which gradually extended to the upper stem and finally becoming soft and watery (Figure 1a). Infected plants were collected from Kapasia of Gazipur district (Latitude 24.266 and Longitude 90.633) to isolate the causal organism. Isolations were carried out following the procedure reported by Briste et al. (2019). Briefly, infected plant parts were surface sterilized in 2% NaOCl for 1 min followed by 70% ethanol for 5 min and rinsed 3 times with sterile double distilled water. A large piece of a surface sterilized plant was cut into small pieces (2 mm × 2 mm) from the margin of the necrotic lesion and placed on half strength potato dextrose agar (PDA) and incubated for 7 days at 25 °C. The BTFD1 and BTFD4 isolates were purified from single spores resulting in white colonies with a growth rate of 1cm/day on PDA (Figure 1b). Colonies produced single celled microconidia from unbranched, short monophialidic conidiophores and septate macroconidia as well as chlamydospores in PDA which is consistent with Fusarium oxysporum (Figure 1c). To confirm the identity of the isolates, the internal transcribed spacer (ITS1, 5.8S rRNA and ITS2) and translation elongation factor-1alpha (EF-1α) were amplified using primers ITS-1/ ITS-4 and EF1-728F/ EF1-986R, respectively (Surovy et al. 2018). The ITS sequences of the isolates BTFD1 and BTFD4 (GenBank accession # MN727096 and MN727095, respectively) showed 100% similarity with the sequence from F. oxysporum strain JJF2 (MN626452). Sequence identity for EF-1α (GenBank accession # MN752123 and MN752124, respectively) was 100% with the sequence from F. oxysporum strain CAV041_EO (MK783088). The isolates (BTFD1 and BTFD4) were identified as F. oxysporum based on the aligned sequences of ITS and EF-1α, molecular phylogenetic analyses by maximum likelihood tree (Figure 2a) and maximum parsimony tree methods (Figure 2b). The isolates were stored at 4°C on dried filter paper as well as in an ultra-low temperature freezer (-80°C) at IBGE, BSMRAU, Bangladesh and are available on request. To ensure pathogenicity, isolate BTFD1 was grown on PDA, incubated at 25°C for 7 days and 250 ml conidial suspension (with 1 × 105 conidia/ml) was prepared. Twelve,three-month-old healthy dragon fruit plants were inoculated. Pathogenicity tests were carried out in two sets using three replications in each set. In one set, only the basal part of the plants was dipped into the conidial suspension and in another set the whole plant was dipped into the conidial suspension for two hours. Sterile distilled water was also used in another set of plants as a control. The inoculated plants were placed on wet tissue in a plastic box (31cm × 24cm × 8cm) covered and incubated at 25°C. After 10 days, all inoculated plants in both sets developed rot symptoms similar to those observed in the field, while the control plants remained healthy (Figure 1d). The pathogen was successfully re-isolated from the inoculated symptomatic parts on half strength PDA medium and had morphology as characterized before, thus fulfilling Koch's postulates. This disease has been reported in Argentina and Malaysia (Wright et al. 2007; Hafifi et al. 2019). To the bet of our knowledge, this is the first report of Fusarium basal rot of dragon fruit in Bangladesh caused by F. oxysporum.
  20. Yang X, Colburn C, Roach K, Zee T, Long S
    Plant Dis, 2023 May 23.
    PMID: 37221241 DOI: 10.1094/PDIS-04-23-0701-PDN
    In February 2023, two Monstera deliciosa Liebm. (Araceae) plants with typical symptoms of leaf rust disease were detected at a grocery store in Oconee Co., South Carolina. Symptoms included chlorotic leaf spots and abundant brownish uredinia, mainly on the adaxial surface of more than 50% of leaves. The same disease was detected on 11 out of 481 M. deliciosa plants in a greenhouse at a plant nursery located in York Co., South Carolina, in March 2023. The first plant sample detected in February was used for morphological characterization, molecular identification, and pathogenicity confirmation of the rust fungus. Urediniospores were densely aggregated, globose, golden to golden brown in color, and measured 22.9 to 27.9 µm (aver. 26.0 ± 1.1 µm; n=50) in diameter with wall thickness at 1.3 to 2.6 µm (aver. 1.8 ± 0.3 µm; n=50). Telia were not observed. These morphological traits aligned with those of Pseudocerradoa paullula (basionym: Puccinia paullula; Ebinghaus et al. 2022; Sakamoto et al. 2023; Sydow and Sydow 1913; Urbina et al. 2023). Genomic DNA was extracted from urediniospores collected from the naturally infected plant sample and used for PCR amplification and DNA sequencing of the large subunit (LSU) genetic marker with primers LRust1R and LR3 (Vilgalys and Hester 1990; Beenken et al. 2012). The LSU sequence of the rust fungus in South Carolina (GenBank accession: OQ746460) is 99.9% identical to that of Ps. paullula voucher BPI 893085 (763/764 nt.; KY764151), 99.4% identical to that of voucher PIGH 17154 in Florida, USA (760/765 nt.; OQ275201), and 99% identical to that of voucher TNS-F-82075 in Japan (715/722 nt.; OK509071). Based on its morphological and molecular characteristics, the causal agent was identified as Ps. paullula. This pathogen identification was also corroborated by the U.S. Department of Agriculture, Animal and Plant Health Inspection Service, Plant Pathogen Confirmatory Diagnostics Laboratory in Laurel, Maryland. To confirm the fungus's pathogenicity on M. deliciosa and M. adansonii Schott (Sakamoto et al. 2023), three plants of each Monstera species were inoculated by spraying with a suspension of urediniospores collected from the original plant sample (1 × 106 spores per ml; approx. 40 ml per plant). Three non-inoculated control plants of each host species were treated with deionized water in the same manner. Plants were placed in a plastic tray with wet paper towels to maintain moisture. The tray was placed at 22C for an 8-h photoperiod and covered for five days to facilitate infection. On 25 days after inoculation, abundant spots bearing urediniospores were produced on all leaves of inoculated M. deliciosa plants. A few uredinia were observed on two of the three inoculated M. adansonii plants. All non-inoculated control plants remained asymptomatic. Morphological features of urediniospores collected from inoculated plants matched those of Ps. paullula used as the inoculum. Aroid leaf rust on Monstera plants was officially reported in Australia, China, Japan, Malaysia, Philippines, and Florida, USA (Shaw 1991; Sakamoto et al. 2023; Urbina et al. 2023). This is the first report of Ps. paullula causing this disease on M. deliciosa in South Carolina, USA. Monstera species are popular indoor and landscape plants. Potential impact and regulatory responses regarding Ps. paullula, a newly introduced and rapidly spreading pathogen in the USA, warrant further evaluation and discussion.
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