1. KAUTIR (Kerala Agricultural University Theses Information and Retrieval)

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    Etiology of the bacterial wilt of ginger incited by Pseudomonas solanacearum E.F. Smith and its control
    (Department of Plant Pathology, College of Agriculture, Vellayani, 1980) Marykutty Samuel; James Mathew
    The bacterial wilt of gingerincited by psuedomonas solanacearum E.P. Smith probably the most serious of all the disease recorded on this crop was first reported from India in 1978. The symptoms of the disease include loss of turgidity of leaves , rolling and yellowing of the leaflets, cropping and wilting of the plant and rotting of the rhizome . No variations in symptoms were observed with the different inclates of the pathogen. Nutrient agar and peptone ceramic acid were the best soild media for the growth of the bacterium . Slight variations in growth were observed among the isolates when grown on ECA medium. The pathogen was identified to be Pseudomonas solanacearum E.P. Smith , biotype -3 of Hayward, from its morphological , physiological and biochemical characters coupled with pathogenicity.
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    Tagging of phytophthor pod rot disease resistance gene in cocoa (Theobroma cacao L.) using ISSR markers
    (Centre for Plant Biotechnology and Molecular Biology, College of Horticulture, Vellanikkara, 2017) Jeughale Kishor, Pundlik; Minimol, J S
    Cocoa (Theobroma cacao L.) known as ‘Chocolate tree’, is a major cash crop in tropical countries. Cocoa production is seriously affected by pod rot diseases caused by many Phytophthora species. Among these, the pod rot caused by Phytophthora palmivora has been reported in India. Yearly losses to the cocoa growers around the world from Phytophthora diseases were assessed at 30 per cent of the total yield loss. Disease resistance can be scored using a number of morphological and physiological characters. However, the morpho-physiological characters greatly depend upon the environment which ultimately affect the experimental data. Hence, confirmation of transfer of genes by tagging with the help of a strong tool is of utmost importance in crop breeding. Molecular markers such as Inter simple sequence repeats (ISSRs) have already proven to be a good tool to detect and tag the genes of interest and will help to reduce the breeding cycle. In this context, the present study was taken up with an objective to develop a strategy to tag gene(s) for Phytophthora pod rot (PPR) resistance in cocoa using ISSR markers. Morphological characterization of 28 hybrid progenies of SVI 1.26 × PII 12.11 was carried out by recording five pod and bean characters. High variability was observed for characters viz., pod weight, pod length and breadth, wet bean weight per pod and single dry bean weight among the progeny of the same cross. Detached pod inoculation technique was adopted to classify the hybrids into resistant and susceptible ones. The wide variability was also recorded for disease reaction among the progenies. Based on the resistance score, three resistant and three susceptible hybrids were selected from the segregating progeny. The eight accessions were screened with fifty ISSR and 15 SSR primers to observe polymorphism between resistance and susceptible genotypes. Polymorphism was observed in 11 ISSR primers and from these, six primers viz., UBC 810, UBC 826, UBC 827, UBC 857, Oligo ISSR 04 and Oligo ISSR 08 were eluted and cloned. Plasmid DNA was isolated from clones and sequenced. Though various SSR primer sets screened were found to yield polymorphism, none of them was successful to give a clear distinction among the resistant and susceptible hybrids. This may be due to the fact that, Quantitative trait loci (QTLs) associated with these reported SSR primers may be absent in the genotypes considered for the study. BLASTn analysis specific to plants was done for all six sequences. Upon analysis, Oligo ISSR 04561 had shown 98 per cent identity with Predicted: T. cacao histidine-containing phosphotransfer protein 1 (HPt). HPts play an important role in propagating cytokinin signal transduction. Cytokinins are instrumental in mediating disease resistance by generating a green island around the infection zones, exhibiting delayed leaf senescence and upregulating the expression of the pathogenesis related (PR) gene/s. In addition to this, the auxin-cytokinin antagonism that occurs as part of a complex hormonal interplay, exerts a critical influence on the core SA-JA/ET plant immunity pathways. The BLASTn analysis of marker UBC 810877 resulted in 99 per cent sequence identity with Predicted: T. cacao phospholipid: diacylglycerol acyltransferase (PDAT) 1 mRNA. This protein regulates the synthesis of triacylglycerol, which is a building component of oils in the plant. Accumulation of oil content in plant cells could impart resistance against the pathogen. UBC 827571 had shown 73 per cent sequence identity with T. cacao clone TCC_BA049P20 complete sequence and it is reported to be QTL rich region associated with different traits of T. cacao. Moreover, ISSR markers UBC 810877, UBC 826535 and UBC 857839 are located on chromosome nine, six and four respectively as inferred from NCBI Genome Data Viewer tool through BLASTn annotations. These markers are found to be located in PPR resistance regions rich in defense associated genes. Further validation and exploitation of polymorphic amplicons or markers in response to PPR would be required. The linkage of Oligo ISSR 04561 and UBC 810877 with HPts and PDAT correspondingly have to be validated to elucidate the association and role of cytokinin and triacylglycerol with PPR disease resistance. If validated, UBC 810877, UBC 826535 and UBC 857839 and Oligo ISSR 04561 could be employed as a marker in PPR resistance breeding programmes in cocoa.
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    Characterization of Mycosphaerella spp. causing sigatoka leaf spot disease complex of banana in Kerala and its management
    (Department of Plant Pathology College of Horticulture, Vellanikkara, 2019) Milsha George; KAU; Anita Cherian, K
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    Biocontrol potential of plant associated bacteria from piper spp. against phytophthora capsici infecting black pepper
    (Department of Agricultural Microbiology, College of Agriculture, Vellayani, 2017) Nadiya Kollakkodan; Anith, K N
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    Pyramiding of bacterial leaf blight resistance genes in rice variety jyothi (PTB 39) through marker assisted selection
    (Centre for Plant Biotechnology and Molecular Biology, College of Horticulture, Vellanikkara, 2017) Kabade Pramod Gorakhanath; Rose Mary Francies
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    Management of collar rot of cowpea caused by rhizoctonia solani kuhn using biofumigants
    (Department of Plant Pathology, College of Agriculture, Vellayani, 2017) Aparna, K P; Girija, V K
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    Pathogenic and genetic variability in Xanthomonas oryzae pv. oryzae (Ishiyama) Swings et al. and the management of bacterial blight disease
    (Department of Plant Pathology, College of Horticulture, Vellanikkara, 2013) Purushothaman, S M; Rehumath Niza, T J
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    Enhancement of resistance to bacterial wilt in tomato by endophytic microbial communities
    (Department of Plant Pathology, College of Horticulture, Vellanikkara, 2015) Deepa James; Sally K Mathew
    The study on “Enhancement of resistance to bacterial wilt in tomato by endophytic microbial communities” was conducted in the Department of Plant Pathology, Department of Agricultural Microbiology, and Centre for Plant Biotechnology and Molecular Biology, College of Horticulture, Vellanikkara during the period 2011-2014. The endophytes were isolated from root and stem of healthy tomato plants from 16 locations of north, central and south Kerala. Endophytic microbial population varied with the plant samples and the population was more in root than stem. Bacterial population was higher than fungi and actinomycetes in root and stem. Among 154 endophytes isolated, 12 out of 79 bacteria, 16 out of 68 fungi, and four out of seven actinomycetes were antagonistic to R. solanacearum in in vitro. Among them, five bacteria, eight fungi, and two actinomycetes were promising in planta. Mutually compatible endophytic isolates were selected for the development of consortia and these were identified based on cultural, morphological and molecular characters. Of the five consortia tested, the one consisted of Trichoderma viride-1, T. viride-2, T. harzianum-1, Bacillus subtilis, and Streptomyces thermodiastaticus showed effect in reducing wilt incidence. Comparative study of the microbial consortium with individual endophytes showed the higher efficacy of consortium in reducing the wilt incidence. The endophytes were reisolated from soil, root, and stem of tomato plants. In pot culture experiment, the consortium applied as seed treatment + seedling dip + soil application at 45 DAP showed the minimum wilt incidence. Studies on the mechanism of antagonism of endophytic isolates showed, positive reaction towards ammonia and negative for HCN and siderophore production. The volatile and nonvolatile metabolites of the endophytes inhibited the pathogen. The endophytes showed varying levels of IAA and salicylic acid production with the maximum in T. harzianum-1 and B. subtilis respectively. Study on the effect of secondary metabolites of endophytes on the disease indicated that, seedlings dipped first in culture filtrate for 2 h and later dipped in bacterial inoculum for 30 min before planting showed the lowest per cent wilt incidence with the minimum for T. viride-2. Induction of systemic resistance was studied by assay of defense related compounds such as phenols, oxidative enzymes and PR proteins. The plants treated with microbial consortium showed higher activity of the defense related compounds with the maximum in plants inoculated with both consortium and pathogen. Field evaluation of endophytic consortium against bacterial wilt showed reduction in wilt incidence of 40.85 per cent in highly susceptible variety, PKM-1, 46.94 per cent in susceptible F1 hybrid, COTH-3, and 52.81 per cent in moderately resistant variety, Mukthi. Thus, the study revealed that, the application of endophytic consortium can enhance the resistance mechanism in tomato against bacterial wilt pathogen, R. solanacearum.