Displaying publications 1 - 20 of 82 in total

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  1. Fulltext Mechanisms of sex determination and transmission ratio distortion in Aedes aegypti
    Hoang KP, Teo TM, Ho TX, Le VS
    Parasit Vectors, 2016 Jan 28;9:49.
    PMID: 26818000 DOI: 10.1186/s13071-016-1331-x
    BACKGROUND: More effective mosquito control strategies are urgently required due to the increasing prevalence of insecticide resistance. The sterile insect technique (SIT) and the release of insects carrying a dominant lethal allele (RIDL) are two proposed methods for environmentally-friendly, species-targeted population control. These methods may be more suitable for developing countries if producers reduce the cost of rearing insects. The cost of control programs could be reduced by producing all-male mosquito populations to circumvent the isolation of females before release without reducing male mating competitiveness caused by transgenes.

    RESULTS: An RNAi construct targeting the RNA recognition motif of the Aedes aegypti transformer-2 (tra-2) gene does not trigger female-to-male sex conversion as commonly observed among dipterous insects. Instead, homozygous insects show greater mortality among m-chromosome-bearing sperm and mm zygotes, yielding up to 100% males in the subsequent generations. The performance of transgenic males was not significantly different to wild-type males in narrow-cage competitive mating experiments.

    CONCLUSION: Our data provide preliminary evidence that the knockdown of Ae. aegypti tra-2 gene expression causes segregation distortion acting at the level of gametic function, which is reinforced by sex-specific zygotic lethality. This finding could promote the development of new synthetic sex distorter systems for the production of genetic sexing mosquito strains.

    Matched MeSH terms: Pest Control, Biological
  2. Sheath blight of rice: a review and identification of priorities for future research
    Singh P, Mazumdar P, Harikrishna JA, Babu S
    Planta, 2019 Nov;250(5):1387-1407.
    PMID: 31346804 DOI: 10.1007/s00425-019-03246-8
    MAIN CONCLUSION: Rice sheath blight research should prioritise optimising biological control approaches, identification of resistance gene mechanisms and application in genetic improvement and smart farming for early disease detection. Rice sheath blight, caused by Rhizoctonia solani AG1-1A, is one of the most devasting diseases of the crop. To move forward with effective crop protection against sheath blight, it is important to review the published information related to pathogenicity and disease management and to determine areas of research that require deeper study. While progress has been made in the identification of pathogenesis-related genes both in rice and in the pathogen, the mechanisms remain unclear. Research related to disease management practices has addressed the use of agronomic practices, chemical control, biological control and genetic improvement: Optimising nitrogen fertiliser use in conjunction with plant spacing can reduce spread of infection while smart agriculture technologies such as crop monitoring with Unmanned Aerial Systems assist in early detection and management of sheath blight disease. Replacing older fungicides with natural fungicides and use of biological agents can provide effective sheath blight control, also minimising environmental impact. Genetic approaches that show promise for the control of sheath blight include treatment with exogenous dsRNA to silence pathogen gene expression, genome editing to develop rice lines with lower susceptibility to sheath blight and development of transgenic rice lines overexpressing or silencing pathogenesis related genes. The main challenges that were identified for effective crop protection against sheath blight are the adaptive flexibility of the pathogen, lack of resistant rice varieties, abscence of single resistance genes for use in breeding and low access of farmers to awareness programmes for optimal management practices.
    Matched MeSH terms: Pest Control, Biological
  3. Antagonistic effects of Streptomyces violaceusniger strain G10 on Fusarium oxysporum f.sp. cubense race 4: indirect evidence for the role of antibiosis in the antagonistic process
    Getha K, Vikineswary S
    J Ind Microbiol Biotechnol, 2002 Jun;28(6):303-10.
    PMID: 12032802
    Fusarium oxysporum f.sp. cubense is the causal pathogen of wilt disease of banana. A cost-effective measure of control for this disease is still not available. Streptomyces violaceusniger strain G10 acts as an antifungal agent antagonistic towards many different phytopathogenic fungi, including different pathogenic races of the Fusarium wilt pathogen. In an attempt to understand the mode of action of this antagonist in nature, the interaction between S. violaceusniger strain G10 and F. oxysporum f.sp. cubense was first studied by paired incubation on agar plates. Evidence for the in vitro antibiosis of strain G10 was demonstrated by inhibition zones in the "cross-plug" assay plates. Microscopic observations showed lysis of hyphal ends in the inhibited fungal colonies. Culture of strain G10 in liquid media produces antifungal metabolites, which showed in vitro antagonistic effects against F. oxysporum f.sp. cubense such as swelling, distortion and excessive branching of hyphae, and inhibition of spore germination. An indirect method was used to show that antibiosis is one of the mechanisms of antagonism by which strain G10 acts against F. oxysporun f.sp. cubense in soil. This study suggests the potential of developing strain G10 for the biological control of Fusarium wilt disease of banana.
    Matched MeSH terms: Pest Control, Biological
  4. Fulltext A preliminary study of the bioactivity of vegetative proteins extracted from Malaysian Bacillus thuringiensis isolates
    Ramasamy B, Nadarajah VD, Soong ZK, Lee HL, Mohammad SM
    Trop Biomed, 2008 Apr;25(1):64-74.
    PMID: 18600206
    Vegetative proteins from Malaysian strains of Bacillus thuringiensis israelensis strains (Bt 11, Bt 12, Bt 15, Bt 16, Bt 17, Bt 21 and Bt 22) and Bacillus sphaericus H-25 strains (Bs 1 and Bs 2) were screened for haemolytic, cytotoxic and larvicidal activity. SDS-PAGE profiles of the Bacillus thuringiensis strains studied consistently showed major bands of 33-37 kDa and 47 kDa. Bt 16 also showed two bands of 66 kDa and 45 kDa similar to the previously reported binary vegetative protein, Vip1Ac (66 kDa) and Vip 2Ac (45 kDa). Both the Bacillus sphaericus strains showed a 35 kDa band that was similiar to a previously reported vegetative protein, the Mtx2 protein. Bs 2 also contains a 37 kDa band, similar to another vegetative protein, the Mtx 3 protein. With the exception of Bt 17 and Bt 21, vegetative proteins from all Bacillus thuringiensis and Bacillus sphaericus strains were highly haemolytic to human erythrocytes, causing more than 75% haemolysis at the highest concentration of 200 microg/ml. High haemolytic activity was associated with high cytotoxic activity with most of the haemolytic strains being indiscriminately cytotoxic to both CEM-SS (human T lymphoblastoid) and HeLa (human uterus cervical cancer) cell lines. Interestingly, the less haemolytic vegetative proteins from Bt 17 and Bt 21 demonstrated cytotoxic activity comparable to that of the highly haemolytic vegetative proteins. Bt 21 displayed toxicity towards both cell lines while Bt 17 was more toxic towards CEM-SS cells. Bioassay against Aedes aegypti and Culex quinquefasciatus larvae revealed that vegetative proteins from the Bacillus thuringiensis strains had activity against both species of larvae but vegetative proteins from Bacillus sphaericus were weakly larvicidal towards Cx. quinquefasciatus only.
    Matched MeSH terms: Pest Control, Biological
  5. Biological control of nematode parasites of small ruminants in Malaysia using the nematophagous fungus Duddingtonia flagrans
    Chandrawathani P, Jamnah O, Waller PJ, Larsen M, Gillespie AT, Zahari WM
    Vet Parasitol, 2003 Nov 14;117(3):173-83.
    PMID: 14630426
    Control of nematode parasites of small ruminants in a wet, tropical environment using the nematophagous fungus, Duddingtonia flagrans, was assessed in this study. Two methods of fungal delivery were tested, namely as a daily feed supplement, or incorporated into feed blocks. Initially, pen trials were conducted with individually penned groups of sheep and goats at dose rates of 125,000 spores and 250,000 spores/kg live weight per day. At the lower dose rate this reduction was between 80 and 90% compared with the pre-treatment levels. At the higher dose rate, there was virtually complete suppression (>99% reduction) of larval recovery. Trials using the fungal feed blocks, showed that when animals were individually penned, they consumed only small amounts of the block (particularly goats), hence little effect on larval recovery in faecal cultures was observed. Grouping animals according to species and dose rate induced satisfactory block consumption and subsequent high levels of larval reduction in faecal cultures. These larval reductions were mirrored by the presence of fungus in faecal cultures. This work was followed by a small paddock trial, whereby three groups of sheep were fed either a feed supplement without fungal spores, supplement with spores, or offered fungal blocks. The dose rate of spores in the latter two groups was 500,000 spores/kg live weight per day. Egg counts were significantly reduced in the two fungal groups, compared with the control group and the latter required two salvage anthelmintic treatments to prevent mortality due to haemonchosis. Pasture larval numbers on the two fungal group plots were also much lower than on the control plot.
    Matched MeSH terms: Pest Control, Biological*
  6. Sharing Malaysian experience with the development of biotechnology-derived food crops
    Abu Bakar UK, Pillai V, Hashim M, Daud HM
    Food Nutr Bull, 2005 Dec;26(4):432-5.
    PMID: 16465992
    Biotechnology-derived food crops are currently being developed in Malaysia mainly for disease resistance and improved post harvest quality. The modern biotechnology approach is adopted because of its potential to overcome constraints faced by conventional breeding techniques. Research on the development of biotechnology-derived papaya, pineapple, chili, passion fruit, and citrus is currently under way. Biotechnology-derived papaya developed for resistance to papaya ringspot virus (PRSV) and improved postharvest qualities is at the field evaluation stage. Pineapple developed for resistance to fruit black heart disorder is also being evaluated for proof-of-concept. Other biotechnology-derived food crops are at early stages of gene cloning and transformation. Activities and products involving biotechnology-derived crops will be fully regulated in the near future under the Malaysian Biosafety Law. At present they are governed only by guidelines formulated by the Genetic Modification Advisory Committee (GMAC), Malaysia. Commercialization of biotechnology-derived crops involves steps that require GMAC approval for all field evaluations and food-safety assessments before the products are placed on the market. Public acceptance of the biotechnology product is another important factor for successful commercialization. Understanding of biotechnology is generally low among Malaysians, which may lead to low acceptance of biotechnology-derived products. Initiatives are being taken by local organizations to improve public awareness and acceptance of biotechnology. Future research on plant biotechnology will focus on the development of nutritionally enhanced biotechnology-derived food crops that can provide more benefits to consumers.
    Matched MeSH terms: Pest Control, Biological
  7. Toxicological and hematological effect of Terminalia arjuna bark extract on a freshwater catfish, Heteropneustes fossilis
    Suely A, Zabed H, Ahmed AB, Mohamad J, Nasiruddin M, Sahu JN, et al.
    Fish Physiol Biochem, 2016 Apr;42(2):431-44.
    PMID: 26501361 DOI: 10.1007/s10695-015-0149-3
    Increasing demand for eco-friendly botanical piscicides and pesticides as replacements for harmful synthetic chemicals has led to investigation of new sources of plant materials. Stem bark of Terminalia arjuna, which has been used as a popular folk medicine since ancient time, was examined for its piscicidal activity. This study aims to determine toxicity of ethanol extract of T. arjuna bark on fresh water stinging catfish (Heteropneustes fossilis), along with evaluation of changes in hematological parameters of the fishes exposed to a lethal concentration. The percent mortality of fishes varied significantly in response to concentrations of the extract and exposure times (between exposure time F = 36.57, p < 0.001; between concentrations F = 39.93, p < 0.001). The lethal concentrations (LC50) of ethanol extract were found to be 12.7, 8.94, 5.63 and 4.71 mg/l for 24, 48, 72 and 96 h, respectively. During acute toxicity test, blood samples of treatment fishes showed significant decreases in the red blood cells count, hematocrit content, hemoglobin concentration, mean corpuscular hemoglobin concentration and plasma protein level when compared to those of the control group, while there were significant increases in the mean corpuscular volume, mean corpuscular hemoglobin, white blood cells count and plasma glucose concentration. These results suggest that T. arjuna bark extract could be considered as a potent piscicide due to its toxic effect on fish, particularly fish hematology.
    Matched MeSH terms: Pest Control, Biological
  8. Fulltext Phytochemical and antimicrobial activity of Swietenia mahagoni crude methanolic seed extract
    Sahgal G, Ramanathan S, Sasidharan S, Mordi MN, Ismail S, Mansor SM
    Trop Biomed, 2009 Dec;26(3):274-9.
    PMID: 20237441 MyJurnal
    The present study was designed to evaluate the antibacterial activities of Swietenia mahagoni crude methanolic (SMCM) seed extract. The antimicrobial activity of the oily extract against Gram-positive, Gram-negative, yeast and fungus strains was evaluated based on the inhibition zone using disc diffusion assay, minimal inhibition concentration (MIC) and minimal bactericidal concentration (MBC) values. The crude extract was subjected to various phytochemicals analysis. The demonstrated qualitative phytochemical tests exhibited the presences of common phytocompounds including alkaloids, terpenoids, antraquinones, cardiac glycosides, saponins, and volatile oils as major active constituents. The SMCM seed extract had inhibitory effects on the growth of Candida albicans, Staphylococcus aureus, Pseudomonas aeroginosa, Streptococcus faecalis and Proteus mirabillase and illustrated MIC and MBC values ranging from 25 mg/ml to 50 mg/ml.
    Matched MeSH terms: Pest Control, Biological
  9. Screening of nematophagous-fungi from fresh faeces of grazing animals and soils
    Farah Haziqah MT, Nur Hikmah AM, Mat Hasan H, Hamdan A, Nik Him NAII
    Trop Biomed, 2019 Sep 01;36(3):687-693.
    PMID: 33597490
    An investigation was undertaken for screening and isolating nematophagous-fungi from the faecal samples of various grazing animals and soils in Malaysia. Total of 111 faeces and 50 soil samples were collected and the samples were cultured on 2% water agar plates. The growth of nematophagous-fungi was stimulated by sprinkling-baiting technique. The conidia of suspected nematophagous-fungi were inoculated on 2% water agar plates. All isolated were maintained on 2% cornmeal agar plates. Verticillium spp., Fusarium spp. and Arthrobotrys spp. were identified from the faecal and soil samples. 62.5% of the faecal samples and 100% of the soil samples were shown to be positive with nematophagous-fungi. This study highlights the present of nematophagous-fungi population in faecal and soil samples. Much study remains to be done to better understanding some fungi especially their mode of action and their predatory behaviour against parasitic nematodes.
    Matched MeSH terms: Pest Control, Biological
  10. Isolation and Identification of novel toxins from a new mosquitocidal isolate from Malaysia, Bacillus thuringiensis subsp. jegathesan
    Kawalek MD, Benjamin S, Lee HL, Gill SS
    Appl Environ Microbiol, 1995 Aug;61(8):2965-9.
    PMID: 7487029
    A new mosquitocidal Bacillus thuringiensis subsp., jegathesan, has recently been isolated from Malaysia. Parasporal crystal inclusions were purified from this strain and bioassayed against fourth-instar larvae of Culex quinquefasciatus, Aedes aegypti, Aedes togoi, Aedes albopictus, Anopheles maculatus, and Mansonia uniformis. The 50% lethal concentration of crystal inclusions for each species was 0.34, 8.08, 0.34, 17.59, 3.91, and 120 ng/ml, respectively. These values show that parasporal inclusions from this new subspecies have mosquitocidal toxicity comparable to that of inclusions isolated from B. thuringiensis subsp. israelensis. Solubilized and chymotrypsin-activated parasporal inclusions possessed low-level hemolytic activity. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed that the crystals were composed of polypeptides of 77, 74, 72, 68, 55, 38, 35, 27, and 23 kDa. Analysis by Western blotting (immunoblotting) with polyclonal antisera raised against toxins purified from B. thuringiensis subsp. israelensis reveals that proteins in parasporal inclusions of subsp. jegathesan are distinct, because little cross-reactivity was shown. Analysis of the plasmid content of B. thuringiensis subsp. jegathesan indicates that the genes for toxin production may be located on 105- to 120-kb plasmids. Cry- clones that have been cured of these plasmids are nontoxic. Southern blot analysis of plasmid and chromosomal DNA from subsp. jegathesan showed little or low homology to the genes coding for CryIVA, CryIVB, and CryIVD from B. thuringiensis subsp. israelensis.
    Matched MeSH terms: Pest Control, Biological
  11. Evidence of natural hybridization between two sympatric sibling species of Bactrocera dorsalis complex based on pheromone analysis
    Wee SL, Tan KH
    J Chem Ecol, 2005 Apr;31(4):845-58.
    PMID: 16124255 DOI: 10.1007/s10886-005-3548-6
    Bactrocera carambolae and B. papayae are major fruit fly pests and sympatric sibling species of the B. dorsalis complex. They possess distinct differences in male pheromonal components. In the 1990's, wild Bactrocera fruit flies with morphological traits intermediate between those of B. carambolae and B. papayae were often captured in traps baited with methyl eugenol (ME). Chemical analyses of rectal glands of ME-fed males revealed that the laboratory Fl, F2, and backcross hybrids possessed ME-derived sex pheromonal components ranging from that typical of B. papayae to that of B. carambolae without any specific trend, which included a combination of pheromonal components from both parental species within an individual hybrid. ME-fed hybrids without any ME-derived pheromonal components were also detected. Further chemical analysis of rectal glands from wild Bactrocera males, after ME feeding in the laboratory, showed a combination of pheromonal components similar to that found in the ME-fed, laboratory-bred hybrids. These findings present circumstantial evidence for the occurrence of a natural hybrid of the two Bactrocera species.
    Matched MeSH terms: Pest Control, Biological
  12. Fulltext Nematophagous fungi as a biological control agent for nematode parasites of small ruminants in Malaysia: a special emphasis on Duddingtonia flagrans
    Chandrawathani P, Jamnah O, Waller PJ, Höglund J, Larsen M, Zahari WM
    Vet Res, 2002 Nov-Dec;33(6):685-96.
    PMID: 12498569
    Approximately 2,800 fresh dung samples from animals, mainly ruminant livestock, were screened for the presence of nematophagous fungi in Malaysia. Arthrobotrys spp. was noted on numerous occasions, but only one isolate of Duddingtonia flagrans was made. For the purposes of producing sufficient quantities of this fungus for feeding trials in sheep, various, commonly available, cheap plant materials were tested as possible growth substrates. This showed that cereal grains (wheat, millet and rice) were the best media for fungal growth. Pen feeding trials were carried out using sheep, both naturally and experimentally infected with nematode parasites (predominantely Haemonchus contortus), to test the efficiency of D. flagrans when administered either in a grain supplement, or incorporated into a feed block. These showed that the fungus survived gut passage in sheep and that dose rates of approximately 1 x 10(6) D. flagrans spores / animal / day, reduced the percentage of infective larvae developing in faecal cultures by more than 90%. These results indicate that using D. flagrans as a biological control agent of nematode parasites, is a promising alternative to nematode parasite control of small ruminants in Malaysia, where anthelmintic resistance is now a major problem.
    Matched MeSH terms: Pest Control, Biological*
  13. Field studies on the biological control of nematode parasites of sheep in the tropics, using the microfungus Duddingtonia flagrans
    Chandrawathani P, Jamnah O, Adnan M, Waller PJ, Larsen M, Gillespie AT
    Vet Parasitol, 2004 Mar 25;120(3):177-87.
    PMID: 15041093
    Long-term field studies were conducted on two government managed small ruminant research farms, located in different geo-climatic regions and approximately 300 km separate from each other, on Peninsula Malaysia. The Infoternak trial (48 weeks) and the Chalok trial (43 weeks) each compared nematode parasite control in separately managed groups of young sheep, either short-term rotationally grazed around a suite of 10 paddocks in addition to receiving a daily supplement of Duddingtonia flagrans spores (Fungus Group); or similar groups of sheep being rotationally grazed alone (Control Group). The prevailing weather conditions at Infoternak farm were of below average rainfall conditions for the most of the trial. As a consequence, only very low worm infections (almost exclusively Haemonchus contortus) were acquired by the 17 sets of tracer lambs that grazed sequentially with the experimental lambs. However on all except 2 occasions in the early part of the trial, the mean tracer worm burdens were significantly lower (P < 0.05) and the experimental lambs grew significantly better (P = 0.054) in the Fungus Group. Rainfall at Chalok farm during the course of the trial was also below average. As a consequence infectivity of pastures was assumed to be relatively low based on faecal egg counts (epg) of the experimental sheep, which following an anthelmintic treatment prior to allocation, remained very low in both treatment groups. Faecal egg counts of undosed replacement lambs in the latter half of the Chalok study, showed a progressive increase in the Control Group to levels exceeding 3000 epg, whereas the Fungus Group remained static at approximately 500 epg. These results show that the deployment of the nematophagous fungus, D. flagrans, can improve the level of parasite control of sheep in the tropics above that which can be achieved by the short-term rotational grazing strategy alone.
    Matched MeSH terms: Pest Control, Biological/methods*
  14. Cross-resistance between a Bacillus thuringiensis Cry toxin and non-Bt insecticides in the diamondback moth
    Sayyed AH, Moores G, Crickmore N, Wright DJ
    Pest Manag Sci, 2008 Aug;64(8):813-9.
    PMID: 18383197 DOI: 10.1002/ps.1570
    Bacillus thuringiensis Berliner (Bt) crystal (Cry) toxins are expressed in various transgenic crops and are also used as sprays in integrated pest management and organic agricultural systems. The diamondback moth (Plutella xylostella L.) is a major worldwide pest of crucifer crops and one that has readily acquired field resistance to a broad range of insecticides.
    Matched MeSH terms: Pest Control, Biological*
  15. Characterization of Streptomyces spp. isolated from the rhizosphere of oil palm and evaluation of their ability to suppress basal stem rot disease in oil palm seedlings when applied as powder formulations in a glasshouse trial
    Shariffah-Muzaimah SA, Idris AS, Madihah AZ, Dzolkhifli O, Kamaruzzaman S, Maizatul-Suriza M
    World J Microbiol Biotechnol, 2017 Dec 18;34(1):15.
    PMID: 29256103 DOI: 10.1007/s11274-017-2396-1
    Ganoderma boninense, the main causal agent of oil palm (Elaeis guineensis) basal stem rot (BSR), severely reduces oil palm yields around the world. To reduce reliance on fungicide applications to control BSR, we are investigating the efficacy of alternative control methods, such as the application of biological control agents. In this study, we used four Streptomyces-like actinomycetes (isolates AGA43, AGA48, AGA347 and AGA506) that had been isolated from the oil palm rhizosphere and screened for antagonism towards G. boninense in a previous study. The aim of this study was to characterize these four isolates and then to assess their ability to suppress BSR in oil palm seedlings when applied individually to the soil in a vermiculite powder formulation. Analysis of partial 16S rRNA gene sequences (512 bp) revealed that the isolates exhibited a very high level of sequence similarity (> 98%) with GenBank reference sequences. Isolates AGA347 and AGA506 showed 99% similarity with Streptomyces hygroscopicus subsp. hygroscopicus and Streptomyces ahygroscopicus, respectively. Isolates AGA43 and AGA48 also belonged to the Streptomyces genus. The most effective formulation, AGA347, reduced BSR in seedlings by 73.1%. Formulations using the known antifungal producer Streptomyces noursei, AGA043, AGA048 or AGA506 reduced BSR by 47.4, 30.1, 54.8 and 44.1%, respectively. This glasshouse trial indicates that these Streptomyces spp. show promise as potential biological control agents against Ganoderma in oil palm. Further investigations are needed to determine the mechanism of antagonism and to increase the shelf life of Streptomyces formulations.
    Matched MeSH terms: Pest Control, Biological/methods*
  16. Genetic and biochemical characterization of field-evolved resistance to Bacillus thuringiensis toxin Cry1Ac in the diamondback moth, Plutella xylostella
    Sayyed AH, Raymond B, Ibiza-Palacios MS, Escriche B, Wright DJ
    Appl Environ Microbiol, 2004 Dec;70(12):7010-7.
    PMID: 15574894
    The long-term usefulness of Bacillus thuringiensis Cry toxins, either in sprays or in transgenic crops, may be compromised by the evolution of resistance in target insects. Managing the evolution of resistance to B. thuringiensis toxins requires extensive knowledge about the mechanisms, genetics, and ecology of resistance genes. To date, laboratory-selected populations have provided information on the diverse genetics and mechanisms of resistance to B. thuringiensis, highly resistant field populations being rare. However, the selection pressures on field and laboratory populations are very different and may produce resistance genes with distinct characteristics. In order to better understand the genetics, biochemical mechanisms, and ecology of field-evolved resistance, a diamondback moth (Plutella xylostella) field population (Karak) which had been exposed to intensive spraying with B. thuringiensis subsp. kurstaki was collected from Malaysia. We detected a very high level of resistance to Cry1Ac; high levels of resistance to B. thuringiensis subsp. kurstaki Cry1Aa, Cry1Ab, and Cry1Fa; and a moderate level of resistance to Cry1Ca. The toxicity of Cry1Ja to the Karak population was not significantly different from that to a standard laboratory population (LAB-UK). Notable features of the Karak population were that field-selected resistance to B. thuringiensis subsp. kurstaki did not decline at all in unselected populations over 11 generations in laboratory microcosm experiments and that resistance to Cry1Ac declined only threefold over the same period. This finding may be due to a lack of fitness costs expressed by resistance strains, since such costs can be environmentally dependent and may not occur under ordinary laboratory culture conditions. Alternatively, resistance in the Karak population may have been near fixation, leading to a very slow increase in heterozygosity. Reciprocal genetic crosses between Karak and LAB-UK populations indicated that resistance was autosomal and recessive. At the highest dose of Cry1Ac tested, resistance was completely recessive, while at the lowest dose, it was incompletely dominant. A direct test of monogenic inheritance based on a backcross of F1 progeny with the Karak population suggested that resistance to Cry1Ac was controlled by a single locus. Binding studies with 125I-labeled Cry1Ab and Cry1Ac revealed greatly reduced binding to brush border membrane vesicles prepared from this field population.
    Matched MeSH terms: Pest Control, Biological*
  17. The potential hazards of Aspergillus sp. in foods and feeds, and the role of biological treatment: a review
    Sheikh-Ali SI, Ahmad A, Mohd-Setapar SH, Zakaria ZA, Abdul-Talib N, Khamis AK, et al.
    J Microbiol, 2014 Oct;52(10):807-18.
    PMID: 25269603 DOI: 10.1007/s12275-014-4294-7
    The contamination of food and feed by Aspergillus has become a global issue with a significant worldwide economic impact. The growth of Aspergillus is unfavourable to the development of food and feed industries, where the problems happen mostly due to the presence of mycotoxins, which is a toxic metabolite secreted by most Aspergillus groups. Moreover, fungi can produce spores that cause diseases, such as allergies and asthma, especially to human beings. High temperature, high moisture, retarded crops, and poor food storage conditions encourage the growth of mold, as well as the development of mycotoxins. A variety of chemical, biological, and physical strategies have been developed to control the production of mycotoxins. A biological approach, using a mixed culture comprised of Saccharomyces cerevisiae and Lactobacillus rhamnosus resulted in the inhibition of the growth of fungi when inoculated into fermented food. The results reveal that the mixed culture has a higher potential (37.08%) to inhibit the growth of Aspergillus flavus (producer of Aflatoxin) compared to either single culture, L. rhamnosus NRRL B-442 and S. cerevisiae, which inhibit the growth by 63.07% and 64.24%, respectively.
    Matched MeSH terms: Pest Control, Biological/methods*
  18. Fulltext Pathogenicity of Nosema sp. (Microsporidia) in the diamondback moth, Plutella xylostella (Lepidoptera: Plutellidae)
    Kermani N, Abu-Hassan ZA, Dieng H, Ismail NF, Attia M, Abd Ghani I
    PLoS One, 2013;8(5):e62884.
    PMID: 23675435 DOI: 10.1371/journal.pone.0062884
    Biological control using pathogenic microsporidia could be an alternative to chemical control of the diamondback moth (DBM) Plutella xylostella (Lepidoptera: Plutellidae). The microsporidium Nosema bombycis (NB) is one of the numerous pathogens that can be used in the Integrated Pest Management (IPM) of DBM. However, its pathogenicity or effectiveness can be influenced by various factors, particularly temperature. This study was therefore conducted to investigate the effect of temperature on NB infection of DBM larvae. Second-instar larvae at different doses (spore concentration: 0, 1×10²,1×10³,1×10⁴, and 1×10⁵) at 15°, 20°, 25°, 30° and 35°C and a relative humidity(RH) of 65% and light dark cycle (L:D) of 12∶12. Larval mortality was recorded at 24 h intervals until the larvae had either died or pupated. The results showed that the spore concentration had a significant negative effect on larval survival at all temperatures, although this effect was more pronounced (92%) at 35°C compared with that at 20 and 30°C (≃50%) and 25°C (26%). Histological observations showed that Nosema preferentially infected the adipose tissue and epithelial cells of the midgut, resulting in marked vacuolization of the cytoplasm. These findings suggest that Nosema damaged the midgut epithelial cells. Our results suggest that Nosema had a direct adverse effect on DBM, and could be utilized as an important biopesticide alternative to chemical insecticides in IPM.
    Matched MeSH terms: Pest Control, Biological/methods*
  19. Malaysian mosquitocidal soil bacterium (Bacillus thuringiensis) strains with selective hemolytic and lectin activity against human and rat erythrocytes
    Nadarajah VD, Chai SH, Mohammed SM, Chan KK, Kanakeswary K
    Southeast Asian J. Trop. Med. Public Health, 2006 Jan;37(1):67-78.
    PMID: 16771215
    The objective of this study is to determine the role of carbohydrates on the toxic effect of parasporal inclusion proteins isolated from Malaysian mosquitocidal Bacillus thuringiensis (Bt) strains on erythrocytes (human and rat). Dose response analyses on the effect of these parasporal inclusions on human and rat erythrocytes suggest that toxin action is selective depending on bacterial strains and source of erythrocytes. Results from this study suggest Bt toxin is a lectin which recognizes specific plasma membrane glycoconjugate receptor(s) with a terminal residue of either D-mannose (Man), N-acetyl-D-galactosamine (GalNAc), N-acetyl-D-glucosamine (GlcNAc) or even a combination of these monosaccharides.
    Matched MeSH terms: Pest Control, Biological/methods*
  20. Biological control of nematode parasites in sheep
    Larsen M
    J Anim Sci, 2006 Apr;84 Suppl:E133-9.
    PMID: 16582084
    In a world in which sheep producers are facing increasing problems due to the rapid spread of anthelmintic resistance, the battle against gastrointestinal parasitic nematodes is a difficult one. One of the potential new tools for integrated control strategies is biological control by means of the nematode-destroying microfungus Duddingtonia flagrans. This fungus forms sticky traps that catch developing larval stages of parasitic nematodes in the fecal environment. When resting spores (chlamydospores) of this fungus are fed daily to grazing animals for a period of time, the pasture infectivity and thus, the worm burden of grazing animals are lowered, especially in young lambs. Research has been conducted throughout the world covering many different climates and management systems. An Australian parasite model showed that if the fungus performs efficiently (> or =90% reduction in worm burden) for 2 or 3 mo, it should contribute significantly to a reduction in the number of dead lambs otherwise occurring when managed only by anthelmintic treatment and grazing management. Feeding or field trials have clearly demonstrated that dosing with a few hundred thousand spores per kilogram of live BW not only reduced the number of infective larvae but also increased the BW of the lambs compared with controls not given fungus. Initial Australian work with feeding spores by means of a block formulation or a slow-release device has shown some promise, but further work is needed to fully develop these delivery systems. In tropical Malaysia, small paddock trials and field studies resulted in significant improvements, in terms of lower worm burdens and increased live BW, when feeding half a million spores daily to grazing lambs. Additional benefits have been observed when the fungus is employed in combination with a fast rotational grazing system. Research has also demonstrated that spores can be delivered in slightly moist feed block material, but only if such blocks are consumed rapidly, because of their very short shelf life. In the northern, temperate Danish climate it has been demonstrated that daily feeding of half a million spores per kilogram of live BW can lead to significant production benefits, with increased live BW gain in fungus-exposed animals. Biological control of parasitic nematodes in sheep seems to hold promise for the future, but to be able to assist producers, the optimal delivery system needs to be refined and further developed. In addition, more work will be needed to define the best use of this technology in different geographic regions.
    Matched MeSH terms: Pest Control, Biological/methods*
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