Browsing by Author "Jayadev, K."

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    Analysis of population structure and genetic relatedness among root (wilt) disease-resistant and susceptible west coast tall coconut palms (Cocos nucifera) using microsatellite markers
    (2011-06) Devakumar, K.; Thomas, R.J.; Nair, R.V.; Augustine Jerard, B.; Rajesh, M.K.; Jacob, P.M.; Jayadev, K.; Parthasarathy, V.A.
    The population structures among the root (wilt) disease-resistant and susceptible coconut palms from 12 locations in the three disease-endemic districts of southern Kerala, were analyzed using nine microsatellite markers. The pair-wise population differentiation estimate (Fs) between the resistant and susceptible populations was 0.021. Two major populations and a subpopulation cluster were identified among the resistant palms. The analysis of genetic relatedness between the resistant mother palms showed that most of the palms located in a single locality shared sib relationship among them. The existence of close genetic relationship among resistant palms from Chengannur, Thiruvalla, Kottayam and Pavukkara localities in Kerala were reported. The results are discussed in terms of breeding strategies for increasing heterozygosity and obtaining the maximum number of disease-resistant seedlings.
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    Assessment of the genetic diversity of Indian coconut accessions and their relationship to other cultivars, using microsatellite markers
    (No. 145 Plant Genetic Resources Newsletter, 2006) Devakumar, K.; Jayadev, K.; Rajesh, M.K.; Chandrasekhar, A.; Manimekalai, R.; Kumaran, P.M.; Parthasarathy, V.A.
    Coconut cultivation in the Indian subcontinent over many centuries has given rise to diverse cultivar types, identi- fied based on discernible morphological traits, geographical locations and farmers’ choice. The Indian coconut germplasm base has also been enriched through introductions from other major coconut growing regions of the world. This study assessed the genetic diversity in a range of coconut accessions, and their relationship to other major coconut cultivars, using microsatellite markers. Microsatellite assay was used for 23 Indian accessions (15 Talls and 6 Dwarfs) and for 21 exotic accessions (18 Talls and 6 Dwarfs). A total of 48 alleles were detected in the Indian accessions by using 8 microsatellite primers (average 6 alleles per locus). More alleles were detected in the Indian accessions than in the exotics, indicating the presence of a wide allelic spectrum in the Indian accessions. Mean gene diversity ranged from 0.00 for ‘Chowghat Green Dwarf’ to 0.59 for ‘Lakshadweep Ordinary Tall’, with an overall mean of 0.32. The within-population variation was slightly higher (53%) than the betweenpopulation variation (47%), suggesting recent local adaptation and subsequent divergence among Indian cultivars. An UPGMA dendrogram separated the Indian accessions into two groups, one clustering with South-east Asian cultivars, which are introgressed types, and another clustering with African and Sri Lankan cultivars. The results are discussed in terms of diversity of Indian coconut accessions and relationships to other major coconut cultivars.
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    DNA amplification fingerprinting in coconut : protocol optimization and analysis of resistance to root (wilt) disease
    (2005) Jayadev, K.; Rajesh, M.K.; Devakumar, K.; Regi Jacob Thomas; Nair, R.V.; Parthasarathy, V.A.
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    Genetic relationship and diversity in Indian coconut accessions based on RAPD markers
    (2004) Anuradha Upadhyay; Jayadev, K.; Manimekalai, R.; Parthasarathy, V.A.
    Randomly amplified polymorphic DNA (RAPD) markers were used to analyze genetic diversity and genetic relationship among coconut accessions. DNA from 81 palms representing 20 accessions, 15 Indian and 5 exotic, was used to amplify with 8 highly polymorphic primers. The 8 primers yielded 77 markers, with an average of 9.6 markers per primer. The within-accession genetic diversity ranged from 0.057 to 0.196. In general, tall accessions were more heterozygous as they had higher proportions of polymorphic bands and genetic diversity. The proportion of variation explained by within accession and between accession diversity was 0.58 and 0.42, respectively. Similarly exotic accessions exhibited more variation. Dwarfs from geographically distant regions did not cluster separately. Based on the similarity matrix, cluster and principal coordinate analysis was performed. A dendrogram of genetic relationship was obtained. The extent of genetic diversity and genetic relationship among accessions is discussed.
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    Improved protocol for AFLP analysis as a base for tagging root (wilt) resistance genes in coconut
    (2002) Rajesh, M.K.; Jayadev, K.; Chandrasekhar, A.; Anuradha Upadhyay; Devakumar, K.; Manimekalai, R.; Nair, R.V.; Parthasarathy, V.A.
    The root (wilt) disease of coconut is endemic in Southern districts of Kerala and the adjoining areas of Tamilnadu causing enonnous loss of nuts. Integrated management practice is the only suggested method to reduce its effect to some extent while development of resistant varieties will offer permanent solution, for which concrete breeding efforts are required. Considering Ute long life cycle of coconut, selection of resistant varieties through conventional methods will be time consuming and laborious. Molecular markers offer numerous advantages over markers traditionally used in plant mapping and selective breeding. AFLP (Amplified Fragment Length Polymorphism) is a versatile DNA fingerprinting technique for marker assisted selection which combines universal applicability with high powers of discrimination and reproducibility. In this preliminary ttudy for tagging root(wh6 resistkce genesiicoconut, AFLP parameters, geirunning a& silver staining conditions were optimized. Also, primer pairs detecting variations between resistant and susceptible palms were selected.
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    In vitro active conservation of immature zygotic embryos of coconut (Cocos nucifera L.) for germplasm collection
    (2004-12) Romila, P.P.; Anitha Karun; Sajini, K.K.; Jayadev, K.
    A protocol for in vitro active conservation of immature zygotic embryos was standardized and observed to be repeatable. Immature embryos collected from 10 and 11 months old nuts of two exotic germplasm viz., Cochin China Tall- (CCNT) and Malayan Yellow Dwarf- (MYD) cultivars of coconut were utilized for the study. Extracted embryos were stored (for 30 days) individually in 5 ml screw capped bottles containing 2 ml of storage medium such as sterile water alone (TI), sterile water with sucrose (7.5 mgfl) (T2), and !A strength of Y3 medium containing activated charcoal but without sucrose (T3). The embryos were retrieved on Y3 medium after one month of storage in different treatment media. Significantly higher percentage of germination and healthy plantlets could be obtained from T2 compared to other two treatments. Germination at 60 days after inoculation was significant with type and age factor. Regarding type, germination was more in Dwarf type (93.7%)whereas for CCNT it was :85.6%. Both shoot and root lengths were found to be significantly different among the three storage media compared.