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Marker-assisted introgression of broad-spectrum blast resistance genes into the cultivated MR219 rice variety

Miah G, Rafii MY, Ismail MR, Puteh AB, Rahim HA, Latif MA

J Sci Food Agric, 2017 Jul;97(9):2810-2818.
PMID: 27778337 DOI: 10.1002/jsfa.8109

BACKGROUND: The rice cultivar MR219 is famous for its better yield and long and fine grain quality; however, it is susceptible to blast disease. The main objective of this study was to introgress blast resistance genes into MR219 through marker-assisted selection (MAS). The rice cultivar MR219 was used as the recurrent parent, and Pongsu Seribu 1 was used as the donor.
RESULTS: Marker-assisted foreground selection was performed using RM6836 and RM8225 to identify plants possessing blast resistance genes. Seventy microsatellite markers were used to estimate recurrent parent genome (RPG) recovery. Our analysis led to the development of 13 improved blast resistant lines with Piz, Pi2 and Pi9 broad-spectrum blast resistance genes and an MR219 genetic background. The RPG recovery of the selected improved lines was up to 97.70% with an average value of 95.98%. Selected improved lines showed a resistance response against the most virulent blast pathogen pathotype, P7.2. The selected improved lines did not express any negative effect on agronomic traits in comparison with MR219.
CONCLUSION: The research findings of this study will be a conducive approach for the application of different molecular techniques that may result in accelerating the development of new disease-resistant rice varieties, which in turn will match rising demand and food security worldwide. © 2016 Society of Chemical Industry.

Matched MeSH terms: Disease Resistance
Fulltext A new insight to biomarkers related to resistance in survived-white spot syndrome virus challenged giant tiger shrimp, Penaeus monodon

Mohd Ghani F, Bhassu S

PeerJ, 2019;7:e8107.
PMID: 31875142 DOI: 10.7717/peerj.8107

The emergence of diseases such as white spot disease has become a threat to Penaeus monodon cultivation. Although there have been a few studies utilizing RNA-Seq, the cellular processes of host-virus interaction in this species remain mostly anonymous. In the present study, P. monodon was challenged with WSSV by intramuscular injection and survived for 12 days. The effect of the host gene expression by WSSV infection in the haemocytes, hepatopancreas and muscle of P. monodon was studied using Illumina HiSeq 2000. The RNA-Seq of cDNA libraries was developed from surviving WSSV-challenged shrimp as well as from normal healthy shrimp as control. A comparison of the transcriptome data of the two groups showed 2,644 host genes to be significantly up-regulated and 2,194 genes significantly down-regulated as a result of the infection with WSSV. Among the differentially expressed genes, our study discovered HMGB, TNFSF and c-Jun in P. monodon as new potential candidate genes for further investigation for the development of potential disease resistance markers. Our study also provided significant data on the differential expression of genes in the survived WSSV infected P. monodon that will help to improve understanding of host-virus interactions in this species.

Matched MeSH terms: Disease Resistance
Effect of dietary prebiotics and probiotics on snakehead (Channa striata) health: Haematology and disease resistance parameters against Aeromonas hydrophila

Munir MB, Hashim R, Nor SAM, Marsh TL

Fish Shellfish Immunol, 2018 Apr;75:99-108.
PMID: 29407616 DOI: 10.1016/j.fsi.2018.02.005

This study examined the effect of dietary prebiotics and probiotics after 16 weeks, followed by 8 weeks of post feeding trial with the control unsupplemented diet on haematological and immune response against Aeromonas hydrophila infection in Channa striata fingerlings. Fish were raised on a 40% protein and 12% lipid feed containing three commercial prebiotics (β-glucan, GOS or galacto-oligosaccharide, MOS or mannan-oligosaccharide); and two probiotics- (Saccharomyces cerevisiae, Lactobacillus acidophilus), respectively and a control. Throughout the study, supplementation with dietary prebiotics and probiotics led to significant (P 

Matched MeSH terms: Disease Resistance/drug effects*
Fulltext Characterization of antiviral T cell responses during primary and secondary challenge of laboratory cats with feline infectious peritonitis virus (FIPV)

Mustaffa-Kamal F, Liu H, Pedersen NC, Sparger EE

BMC Vet Res, 2019 May 22;15(1):165.
PMID: 31118053 DOI: 10.1186/s12917-019-1909-6

BACKGROUND: Feline infectious peritonitis (FIP) is considered highly fatal in its naturally occurring form, although up to 36% of cats resist disease after experimental infection, suggesting that cats in nature may also resist development of FIP in the face of infection with FIP virus (FIPV). Previous experimental FIPV infection studies suggested a role for cell-mediated immunity in resistance to development of FIP. This experimental FIPV infection study in specific pathogen free (SPF) kittens describes longitudinal antiviral T cell responses and clinical outcomes ranging from rapid progression, slow progression, and resistance to disease.
RESULTS: Differences in disease outcome provided an opportunity to investigate the role of T cell immunity to FIP determined by T cell subset proliferation after stimulation with different viral antigens. Reduced total white blood cell (WBC), lymphocyte and T cell counts in blood were observed during primary acute infection for all experimental groups including cats that survived without clinical FIP. Antiviral T cell responses during early primary infection were also similar between cats that developed FIP and cats remaining healthy. Recovery of antiviral T cell responses during the later phase of acute infection was observed in a subset of cats that survived longer or resisted disease compared to cats showing rapid disease progression. More robust T cell responses at terminal time points were observed in lymph nodes compared to blood in cats that developed FIP. Cats that survived primary infection were challenged a second time to pathogenic FIPV and tested for antiviral T cell responses over a four week period. Nine of ten rechallenged cats did not develop FIP or T cell depletion and all cats demonstrated antiviral T cell responses at multiple time points after rechallenge.
CONCLUSIONS: In summary, definitive adaptive T cell responses predictive of disease outcome were not detected during the early phase of primary FIPV infection. However emergence of antiviral T cell responses after a second exposure to FIPV, implicated cellular immunity in the control of FIPV infection and disease progression. Virus host interactions during very early stages of FIPV infection warrant further investigation to elucidate host resistance to FIP.

Matched MeSH terms: Disease Resistance/immunology
Fulltext Molecular characterization and screening for sheath blight resistance using Malaysian isolates of Rhizoctonia solani

Nadarajah K, Omar NS, Rosli MM, Shin Tze O

Biomed Res Int, 2014;2014:434257.
PMID: 25258710 DOI: 10.1155/2014/434257

Two field isolates of Rhizoctonia solani were isolated from infected paddy plants in Malaysia. These isolates were verified via ITS-rDNA analysis that yielded ~720 bp products of the ITS1-5.8S-ITS4 region, respectively. The sequenced products showed insertion and substitution incidences which may result in strain diversity and possible variation in disease severity. These strains showed some regional and host-specific relatedness via Maximum Likelihood and further phylogenetic analysis via Maximum Parsimony showed that these strains were closely related to R. solani AG1-1A (with 99-100% identity). Subsequent to strain verification and analysis, these isolates were used in the screening of twenty rice varieties for tolerance or resistance to sheath blight via mycelial plug method where both isolates (1801 and 1802) showed resistance or moderate resistance to Teqing, TETEP, and Jasmine 85. Isolate 1802 was more virulent based on the disease severity index values. This study also showed that the mycelial plug techniques were efficient in providing uniform inoculum and humidity for screening. In addition this study shows that the disease severity index is a better mode of scoring for resistance compared to lesion length. These findings will provide a solid basis for our future breeding and screening activities at the institution.

Matched MeSH terms: Disease Resistance/genetics*; Disease Resistance/immunology
Fulltext Expression patterns of genes involved in the defense and stress response of Spiroplasma citri infected Madagascar Periwinkle Catharanthus roseus

Nejat N, Vadamalai G, Dickinson M

Int J Mol Sci, 2012;13(2):2301-2313.
PMID: 22408455 DOI: 10.3390/ijms13022301

Madagascar periwinkle is an ornamental and a medicinal plant, and is also an indicator plant that is highly susceptible to phytoplasma and spiroplasma infections from different crops. Periwinkle lethal yellows, caused by Spiroplasma citri, is one of the most devastating diseases of periwinkle. The response of plants to S. citri infection is very little known at the transcriptome level. In this study, quantitative real-time PCR (RT-qPCR) was used to investigate the expression levels of four selected genes involved in defense and stress responses in naturally and experimentally Spiroplasma citri infected periwinkles. Strictosidine β-glucosidase involved in terpenoid indole alkaloids (TIAs) biosynthesis pathway showed significant upregulation in experimentally and naturally infected periwinkles. The transcript level of extensin increased in leaves of periwinkles experimentally infected by S. citri in comparison to healthy ones. A similar level of heat shock protein 90 and metallothionein expression was observed in healthy, naturally and experimentally spiroplasma-diseased periwinkles. Overexpression of Strictosidine β-glucosidase demonstrates the potential utility of this gene as a host biomarker to increase the fidelity of S. citri detection and can also be used in breeding programs to develop stable disease-resistance varieties.

Matched MeSH terms: Disease Resistance/genetics*
Fulltext Development of a New Molecular Marker for the Resistance to Tomato Yellow Leaf Curl Virus

Nevame AYM, Xia L, Nchongboh CG, Hasan MM, Alam MA, Yongbo L, et al.

Biomed Res Int, 2018;2018:8120281.
PMID: 30105248 DOI: 10.1155/2018/8120281

Tomato yellow leaf curl virus (TYLCV) responsible for tomato yellow leaf curl disease (TYLCD) causes a substantial decrease in tomato (Solanum lycopersicum L.) yield worldwide. The use of resistant variety as a sustainable management strategy has been advocated. Tremendous progress has been made in genetically characterizing the resistance genes (R gene) in tomato. Breeding tomato for TYLCV resistance has been based mostly on Ty-3 as a race-specific resistance gene by introgression originating from wild tomato species relatives. Improvement or development of a cultivar is achievable through the use of marker-assisted selection (MAS). Therefore, precise and easy use of gene-targeted markers would be of significant importance for selection in breeding programs. The present study was undertaken to develop a new marker based on Ty-3 gene sequence that can be used for MAS in TYLCV resistant tomato breeding program. The new developed marker was named ACY. The reliability and accuracy of ACY were evaluated against those of Ty-3 linked marker P6-25 through screening of commercial resistant and susceptible tomato hybrids, and genetic segregation using F2 population derived from a commercial resistant hybrid AG208. With the use of bioinformatics and DNA sequencing analysis tools, deletion of 10 nucleotides was observed in Ty-3 gene sequence for susceptible tomato variety. ACY is a co-dominant indel-based marker that produced clear and strong polymorphic band patterns for resistant plant distinguishing it from its susceptible counterpart. The obtained result correlates with 3:1 segregation ratio of single resistant dominant gene inheritance, which depicted ACY as gene-tag functional marker. This marker is currently in use for screening 968 hybrids varieties and one thousand breeding lines of tomato varieties stocked in Jiangsu Green Port Modern Agriculture Development Company (Green Port). So far, ACY has been used to identify 56 hybrids and 51 breeding lines. These newly detected breeding lines were regarded as potential source of resistance for tomato breeding. This work exploited the sequence of Ty-3 and subsequently contributed to the development of molecular marker ACY to aid phenotypic selection. We thus recommend this marker to breeders, which is suitable for marker-assisted selection in tomato.

Matched MeSH terms: Disease Resistance/genetics*
Involvement of metabolites in early defense mechanism of oil palm (Elaeis guineensis Jacq.) against Ganoderma disease

Nusaibah SA, Siti Nor Akmar A, Idris AS, Sariah M, Mohamad Pauzi Z

Plant Physiol Biochem, 2016 Dec;109:156-165.
PMID: 27694009 DOI: 10.1016/j.plaphy.2016.09.014

Understanding the mechanism of interaction between the oil palm and its key pathogen, Ganoderma spp. is crucial as the disease caused by this fungal pathogen leads to a major loss of revenue in leading palm oil producing countries in Southeast Asia. Here in this study, we assess the morphological and biochemical changes in Ganoderma disease infected oil palm seedling roots in both resistant and susceptible progenies. Rubber woodblocks fully colonized by G. boninense were applied as a source of inoculum to artificially infect the roots of resistant and susceptible oil palm progenies. Gas chromatography-mass spectrometry was used to measure an array of plant metabolites in 100 resistant and susceptible oil palm seedling roots treated with pathogenic Ganoderma boninense fungus. Statistical effects, univariate and multivariate analyses were used to identify key-Ganoderma disease associated metabolic agitations in both resistant and susceptible oil palm root tissues. Ganoderma disease related defense shifts were characterized based on (i) increased antifungal activity in crude extracts, (ii) increased lipid levels, beta- and gamma-sitosterol particularly in the resistant progeny, (iii) detection of heterocyclic aromatic organic compounds, benzo [h] quinoline, pyridine, pyrimidine (iv) elevation in antioxidants, alpha- and beta-tocopherol (iv) degraded cortical cell wall layers, possibly resulting from fungal hydrolytic enzyme activity needed for initial penetration. The present study suggested that plant metabolites mainly lipids and heterocyclic aromatic organic metabolites could be potentially involved in early oil palm defense mechanism against G. boninense infection, which may also highlight biomarkers for disease detection, treatment, development of resistant variety and monitoring.

Matched MeSH terms: Disease Resistance*
Fulltext Identification of quantitative trait loci for blast resistance in BC₂F₃ and BC₂F5 advanced backcross families of rice

Rahim HA, Bhuiyan MA, Lim LS, Sabu KK, Saad A, Azhar M, et al.

Genet. Mol. Res., 2012;11(3):3277-89.
PMID: 23079822 DOI: 10.4238/2012.September.12.11

Advanced backcross families derived from Oryza sativa cv MR219/O. rufipogon IRGC105491 were utilized for identification of quantitative trait loci (QTL) for blast resistance using simple sequence repeat markers. Two hundred and sixty-one BC(2)F(3) families were used to construct a linkage map, using 87 markers, which covered 2375.2 cM of 12 rice chromosomes, with a mean density of 27.3 cM. The families were evaluated in a greenhouse for resistance to blast disease caused by pathotypes P7.2 and P5.0 of Magnaporthe oryzae. Five QTLs (qBL5.1, qBL5.2, qBL6.1, qBL8.1, and qBL10.1) for pathotype P5.0 and four QTLs (qBL5.3, qBL5.4, qBL7.1, and qBL8.2) for pathotype P7.2 were identified using the BC(2)F(3) families. Another linkage map was also constructed based on 31 BC(2)F(5) families, using 63 SSR markers, which covered 474.9 cM of 9 rice chromosomes, with a mean density of 8.01 cM. Five suggestive QTLs (qBL11.2, qBL11.3, qBL12.1, qBL12.2, qBL12.3) and one putative QTL (qBL2.1) were identified for pathotype P7.2. Also, seven suggestive QTLs (qBL1.1, qBL2.2, qBL4.1, qBL4.2, qBL5.3, qBL8.3, and qBL11.1) were detected for pathotype P5.0. We conclude that there is a non-race-specific resistance spectrum of O. rufipogon against M. oryzae pathotypes.

Matched MeSH terms: Disease Resistance/genetics*
Fulltext Draft genome sequence of the rubber tree Hevea brasiliensis

Rahman AY, Usharraj AO, Misra BB, Thottathil GP, Jayasekaran K, Feng Y, et al.

BMC Genomics, 2013;14:75.
PMID: 23375136 DOI: 10.1186/1471-2164-14-75

Hevea brasiliensis, a member of the Euphorbiaceae family, is the major commercial source of natural rubber (NR). NR is a latex polymer with high elasticity, flexibility, and resilience that has played a critical role in the world economy since 1876.

Matched MeSH terms: Disease Resistance/genetics
Fulltext GanoCare® Improves Oil Palm Growth and Resistance against Ganoderma Basal Stem Rot Disease in Nursery and Field Trials

Rebitanim NA, Hanafi MM, Idris AS, Abdullah SNA, Mohidin H, Rebitanim NZ

Biomed Res Int, 2020;2020:3063710.
PMID: 32420335 DOI: 10.1155/2020/3063710

Basal stem rot (BSR) caused by Ganoderma boninense is a major threat to sustainable oil palm production especially in Southeast Asia and has brought economic losses to the oil palm industry around the world. With no definitive cure at present, this study introduces a new fertilizer technology called GanoCare®, as an effort to suppress BSR incidence in oil palm. Experiments were carried out to evaluate the effect of GanoCare® on growth, physiology, and BSR disease suppression using sitting technique in the oil palm nursery stage. A follow-up using similar treatments was carried out in the field to test on severity of Ganoderma using baiting technique under natural condition. Treatments tested were 10 g/month and 30 g/three months given as pretreatment only or continuous treatment. Results showed that GanoCare® increased the height, bulb diameter, leaf area, chlorophyll content, photosynthesis rate, and fresh and dry weight of the leaf, bole, and root of oil palm seedlings in the nursery trial. Seedlings treated with GanoCare® exhibited reduced percentage of disease severity, incidence, and dead seedlings, compared to the control. In nursery and field, lowest percentage of dead seedlings due to Ganoderma was found in seedlings given combination of pretreatment and continuous treatment of 30 g/three months (T4) with 5.56 and 6.67%, while control seedlings significantly marked the maximum percentage of 94.45 and 93.33%. The most successful treatment in both nursery and field was T4 with disease reductions of 77.78 and 82.36%, respectively, proving that nutrients contained in GanoCare® are essential in allowing better development of a strong defense system in the seedlings.

Matched MeSH terms: Disease Resistance/drug effects*
Fulltext Breeding for Anthracnose Disease Resistance in Chili: Progress and Prospects

Ridzuan R, Rafii MY, Ismail SI, Mohammad Yusoff M, Miah G, Usman M

Int J Mol Sci, 2018 Oct 11;19(10).
PMID: 30314374 DOI: 10.3390/ijms19103122

Chili anthracnose is one of the most devastating fungal diseases affecting the quality and yield production of chili. The aim of this review is to summarize the current knowledge concerning the chili anthracnose disease, as well as to explore the use of marker-assisted breeding programs aimed at improving anthracnose disease resistance in this species. This disease is caused by the Colletotrichum species complex, and there have been ongoing screening methods of chili pepper genotypes with resistance to anthracnose in the field, as well as in laboratories. Conventional breeding involves phenotypic selection in the field, and it is more time-consuming compared to molecular breeding. The use of marker-assisted selection (MAS) on the basis of inheritance, the segregation ratio of resistance to susceptibility, and the gene-controlling resistance may contribute to the development of an improved chili variety and speed up the selection process, while also reducing genetic drag in the segregating population. More importantly, by using molecular markers, the linkage groups are determined dominantly and co-dominantly, meaning that the implementation of a reliable method to produce resistant varieties is crucial in future breeding programs. This updated information will offer a supportive direction for chili breeders to develop an anthracnose-resistant chili variety.

Matched MeSH terms: Disease Resistance/genetics*
Fulltext Comparative genomic and transcriptomic analysis of selected fatty acid biosynthesis genes and CNL disease resistance genes in oil palm

Rosli R, Amiruddin N, Ab Halim MA, Chan PL, Chan KL, Azizi N, et al.

PLoS One, 2018;13(4):e0194792.
PMID: 29672525 DOI: 10.1371/journal.pone.0194792

Comparative genomics and transcriptomic analyses were performed on two agronomically important groups of genes from oil palm versus other major crop species and the model organism, Arabidopsis thaliana. The first analysis was of two gene families with key roles in regulation of oil quality and in particular the accumulation of oleic acid, namely stearoyl ACP desaturases (SAD) and acyl-acyl carrier protein (ACP) thioesterases (FAT). In both cases, these were found to be large gene families with complex expression profiles across a wide range of tissue types and developmental stages. The detailed classification of the oil palm SAD and FAT genes has enabled the updating of the latest version of the oil palm gene model. The second analysis focused on disease resistance (R) genes in order to elucidate possible candidates for breeding of pathogen tolerance/resistance. Ortholog analysis showed that 141 out of the 210 putative oil palm R genes had homologs in banana and rice. These genes formed 37 clusters with 634 orthologous genes. Classification of the 141 oil palm R genes showed that the genes belong to the Kinase (7), CNL (95), MLO-like (8), RLK (3) and Others (28) categories. The CNL R genes formed eight clusters. Expression data for selected R genes also identified potential candidates for breeding of disease resistance traits. Furthermore, these findings can provide information about the species evolution as well as the identification of agronomically important genes in oil palm and other major crops.

Matched MeSH terms: Disease Resistance/genetics*
Fulltext Enhancement of Live Food Nutritional Status with Essential Nutrients for Improving Aquatic Animal Health: A Review

Samat NA, Yusoff FM, Rasdi NW, Karim M

Animals (Basel), 2020 Dec 21;10(12).
PMID: 33371528 DOI: 10.3390/ani10122457

At the present time, no artificial larval diet is capable of entirely fulfilling the dietary requirements of several larval fish and crustacean species. Zooplankton live food is the basic foundation of fish larviculture, and successful rearing of fish larvae still heavily depends on an adequate supply of nutritious live food. Despite being important, the production protocols of copepods and cladocerans (Moina) are still underdeveloped in hatcheries. Rotifers and Artemia are the most commonly used live foods. However, these live foods are evidently lacking in crucial nutrient constituents. Hence, through nutrient enrichment, live food with the nutritional profile that meets the requirements of fish larvae can be produced. With the aim to maximize the effectiveness of production to optimize profitability, it is important to evaluate and improve culture techniques for the delivery of micro- and macro-nutrients as feed supplements to larvae in aquaculture systems. Bioencapsulation and enrichment are the evolving techniques in aquaculture that are commonly employed to enhance the nutritional quality of live food by integrating nutrients into them, which subsequently improves the growth, survival, and disease resistance of the consuming hosts. This review aims to highlight some of the approaches and methods used to improve the nutritional quality of live food by modifying their nutrient composition, which could have immense promise in the enhancement of aquatic animal health.

Matched MeSH terms: Disease Resistance
Dietary Euphorbia hirta Extract Improved the Resistance of Sharptooth Catfish Clarias gariepinus to Aeromonas hydrophila

Sheikhlar A, Meng GY, Alimon R, Romano N, Ebrahimi M

J Aquat Anim Health, 2017 Dec;29(4):225-235.
PMID: 28937913 DOI: 10.1080/08997659.2017.1374310

Aqueous and methanol extracts of lemon Citrus limon peel, Euphorbia hirta (aerial parts), and fenugreek Trigonella foenum-graecum seeds were tested for their in vitro antimicrobial activities against the bacterium Aeromonas hydrophila. A swab paper disk method showed that the methanol extract of E. hirta (EHE) had the largest inhibition zone and the lowest minimal inhibitory concentration compared to all other herbal extracts. Based on these results, EHE was included in the diets of Sharptooth Catfish Clarias gariepinus at 0 (control), 2, 5, or 7 g/kg of diet (experiment 1). Each treatment was conducted in triplicate, with 30 fish (mean weight ± SE = 9.4 ± 0.4 g) in each replicate. After 30 d, the growth, feed intake, hepatosomatic index (HSI), and plasma biochemical parameters were measured. With a separate batch of Sharptooth Catfish, the efficacy of the EHE diets in conferring fish resistance to A. hydrophila over 30 d was compared to that of a diet containing oxytetracycline (OTC; experiment 2). Six treatments were conducted in triplicate groups of 30 fish (mean weight ± SE = 9.0 ± 0.3 g); the Control fish were fed the control diet and were not injected with A. hydrophila, while the Control-AH and OTC-AH groups were infected with A. hydrophila and were fed either the control diet or the diet containing OTC at 1 g/199 g. The other three treatments included fish that were injected with A. hydrophila but fed diets with increasing EHE at 2, 5, or 7 g/kg. Experiment 1 showed no change to growth, feeding efficiency, HSI, or plasma biochemical parameters. In experiment 2, however, fish that were fed dietary EHE at 5 g/kg had significantly lower mortality than the Control-AH group, with further resistance observed for fish fed EHE at 7 g/kg. Dietary OTC was more effective than EHE as a prophylactic to A. hydrophila infection in Sharptooth Catfish. Nevertheless, EHE can potentially be a valuable dietary supplement to improve the resistance of Sharptooth Catfish to A. hydrophila infection. Received May 3, 2017; accepted August 24, 2017.

Matched MeSH terms: Disease Resistance*
Fulltext Pathotype Identification of Rice Blast Pathogen, Pyricularia oryzae Using Differential Varieties in Peninsular Malaysia

Siti Norsuha Misman, Latiffah Zakaria

Trop Life Sci Res, 2019;30(2):181-190.
MyJurnal

Seven pathotypes of Pyricularia oryzae were differentiated from blast disease samples collected from 2014–2016, using eight Malaysian differential rice varieties. Pathotype P7.0 is the dominant pathotype identified (33.9%) followed by P0.0, P1.0 and P9.0 which are currently become more abundant in the field with frequency of 20.0% for P0.0, and 15.4% for both P1.0 and P9. Pathotype P7.0 was mostly isolated from MR220CL2, MR263 and MR219 rice varieties which are popular variety planted by farmers in Peninsular Malaysia. Interestingly, new emergence of pathotype P0.2 has been identified, which was isolated from a new released variety, MR284 as well as blast isogenic line IRBL 20 carrying Pi5(t) blast resistance gene. Prolong planting of more than 20 planting seasons and large scale planting of MR219 and MR220 with current varietal coverage areas of more than 90% in Peninsular Malaysia are suspected as possible reason for P7.0 become dominant. Varietal coverage of MR220CL2 and MR263 has reached about 50% might be the cause of changes in blast pathogen pathotype dominancy to P0.0, P1.0 and P9.0.

Matched MeSH terms: Disease Resistance
Identification of the amino acids in the Major Histocompatibility Complex class II region of Scottish Blackface sheep that are associated with resistance to nematode infection

Stear A, Ali AOA, Brujeni GN, Buitkamp J, Donskow-Łysoniewska K, Fairlie-Clarke K, et al.

Int J Parasitol, 2019 09;49(10):797-804.
PMID: 31306661 DOI: 10.1016/j.ijpara.2019.05.003

Lambs with the Major Histocompatibility Complex DRB1*1101 allele have been shown to produce fewer nematode eggs following natural and deliberate infection. These sheep also possess fewer adult Teladorsagia circumcincta than sheep with alternative alleles at the DRB1 locus. However, it is unclear if this allele is responsible for the reduced egg counts or merely acts as a marker for a linked gene. This study defined the MHC haplotypes in a population of naturally infected Scottish Blackface sheep by PCR amplification and sequencing, and examined the associations between MHC haplotypes and faecal egg counts by generalised linear mixed modelling. The DRB1*1101 allele occurred predominately on one haplotype and a comparison of haplotypes indicated that the causal mutation or mutations occurred in or around this locus. Additional comparisons with another resistant haplotype indicated that mutations in or around the DQB2*GU191460 allele were also responsible for resistance to nematode infections. Further analyses identified six amino acid substitutions in the antigen binding site of DRB1*1101 that were significantly associated with reductions in the numbers of adult T. circumcincta.

Matched MeSH terms: Disease Resistance/genetics; Disease Resistance/immunology
Rapid cloning of disease-resistance genes in plants using mutagenesis and sequence capture

Steuernagel B, Periyannan SK, Hernández-Pinzón I, Witek K, Rouse MN, Yu G, et al.

Nat Biotechnol, 2016 Jun;34(6):652-5.
PMID: 27111722 DOI: 10.1038/nbt.3543

Wild relatives of domesticated crop species harbor multiple, diverse, disease resistance (R) genes that could be used to engineer sustainable disease control. However, breeding R genes into crop lines often requires long breeding timelines of 5-15 years to break linkage between R genes and deleterious alleles (linkage drag). Further, when R genes are bred one at a time into crop lines, the protection that they confer is often overcome within a few seasons by pathogen evolution. If several cloned R genes were available, it would be possible to pyramid R genes in a crop, which might provide more durable resistance. We describe a three-step method (MutRenSeq)-that combines chemical mutagenesis with exome capture and sequencing for rapid R gene cloning. We applied MutRenSeq to clone stem rust resistance genes Sr22 and Sr45 from hexaploid bread wheat. MutRenSeq can be applied to other commercially relevant crops and their relatives, including, for example, pea, bean, barley, oat, rye, rice and maize.

Matched MeSH terms: Disease Resistance/genetics*
Genetic analyses of resistance against Leptopilina victoriae in Drosophila bipectinata

Takigahira T, Kohyama TI, Suwito A, Kimura MT

Genetica, 2015 Jun;143(3):279-85.
PMID: 25663497 DOI: 10.1007/s10709-015-9824-7

Drosophila bipectinata from Iriomote-jima (IR) is susceptible to the endoparasitoid Leptopilina victoriae from Kota Kinabalu (L. victoriae KK), but D. bipectinata from Kota Kinabalu (KK) and Bogor (BG) is resistant. The cross experiments between the resistant (KK) and susceptible (IR) populations of D. bipectinata suggested that the resistance to this parasitoid is a dominant trait and controlled by a single locus or few linked loci on an autosome. In the AFLP analysis using the IR, KK and BG populations of D. bipectinata and the resistant and susceptible populations derived from a mixed population of these three geographic populations, a DNA fragment almost specific to susceptible flies was detected. It also revealed that genes from the IR population were more frequently maintained in the mixed population compared with those from the KK and BG populations, suggesting that at least a number of genes from the IR population are more advantageous under the laboratory conditions. This explains our previous results that the resistance was lowered in the mixed population although the resistance itself is suggested to incur only low costs; i.e., the resistance gene(s) from the KK and BG populations would have been linked with some genes that are disadvantageous under the laboratory conditions.

Matched MeSH terms: Disease Resistance/genetics*
Current advance methods for the identification of blast resistance genes in rice

Tanweer FA, Rafii MY, Sijam K, Rahim HA, Ahmed F, Latif MA

C. R. Biol., 2015 May;338(5):321-34.
PMID: 25843222 DOI: 10.1016/j.crvi.2015.03.001

Rice blast caused by Magnaporthe oryzae is one of the most devastating diseases of rice around the world and crop losses due to blast are considerably high. Many blast resistant rice varieties have been developed by classical plant breeding and adopted by farmers in various rice-growing countries. However, the variability in the pathogenicity of the blast fungus according to environment made blast disease a major concern for farmers, which remains a threat to the rice industry. With the utilization of molecular techniques, plant breeders have improved rice production systems and minimized yield losses. In this article, we have summarized the current advanced molecular techniques used for controlling blast disease. With the advent of new technologies like marker-assisted selection, molecular mapping, map-based cloning, marker-assisted backcrossing and allele mining, breeders have identified more than 100 Pi loci and 350 QTL in rice genome responsible for blast disease. These Pi genes and QTLs can be introgressed into a blast-susceptible cultivar through marker-assisted backcross breeding. These molecular techniques provide timesaving, environment friendly and labour-cost-saving ways to control blast disease. The knowledge of host-plant interactions in the frame of blast disease will lead to develop resistant varieties in the future.

Matched MeSH terms: Disease Resistance/genetics*

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