Browsing by Author "Devakumar, K."

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    Analysis of genetic diversity among Indian Ocean coconut accessions through microsatellite markers
    (2016-03) Devakumar, K.; Neema Babu; Uma Maheswari, T.S.; Naganeeswaran, S.; Niral, V.; Augustine Jerard, B.
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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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    A durable pollination raincoat for hybridization during monsoon in coconut
    (2020) Devakumar, K.; Regi Jacob Thomas; Anitha Karun
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    An improved device for coconut embryo extraction
    (2017-12) Devakumar, K.; Neema, M.; Aparna, V.; Krishna Prakash; Gangaraj, K.P.; Anitha Karun
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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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    IND 030-Laccadive Micro Tall (IC0430669; INGR13060), a Coconut (Cocos nucifera) Germplasm with Cluster Bearing Heavy Bunches of Micro Nuts
    (2014) Niral, V.; Augustine Jerard, B.; Samsudeen, K.; Nair, R.V.; Jacob, P.M.; Devakumar, K.; Ratnambal, M.J.; Kumaran, P.M.; Bhaskara Rao, E.V.V.; Pillai, R.V.; George V. Thomas
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    IND 221 – Andaman Horned Cocos (IC0598221; INGR13063), a Coconut (Cocos nucifera) Germplasm with Distinct Character of Horny Nuts
    (2014) Augustine Jerard, B.; Niral, V.; Damodaran, V.; Arunachalam, V.; Rajesh, M.K.; Samsudeen, K.; Dhanapal, R.; Devakumar, K.; Nair, R.V.; Kumaran, P.M.; George V. Thomas
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    Microsatellite analysis of distinct coconut accessions from Agatti and Kavaratti Islands, Lakshadweep, India
    (Elsevier, 2010) Devakumar, K.; Niral, V.; Augustine Jerard, B.; Jayabose, C.; Chandra Mohanan, R.; Jacob, P.M.
    The Lakshadweep group of islands, located in the south-western part of India in the Indian Ocean is considered unique for its coconut populations owing to its geographic isolation and assumed introgression with mainland coconut populations along west coast of mainland India. A wide range of variability was noticed for morphological characters of Lakshadweep coconut populations. A total of nine accessions were collected from Agatti and Kavaratti Islands of Lakshadweep as part of a germplasm enrichment programme for island coconut populations of India. This includes three Laccadive Micro types, four types of Laccadive Ordinary Tall differing in nut bearing habit, fruit shape and size, one each of sweet husked Kaithathali tall and dwarf type. The microsatellite analysis of the 9 coconut populations with 8 primers revealed a total of 37 alleles. The highest number of eight alleles was detected for the CAC8 primer and the lowest number of three alleles for the CAC10, CAC13 and CnCIRG11 primers. The estimate of heterozygosity was highest (>0.5) for the two Laccadive Micro Tall (LMT02 and LMT03) and the Laccadive Small Tall (LCT02) populations and was lowest (0.24) for the Laccadive Micro Tall (LMT01). The sporadic occurrence of Laccadive Micro Tall is discussed in the context of high outcrossing and inbreeding depression.
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    Modified Ground Pollination Technique for Hybridization in Coconut
    (2019-12) Thomas, R.J.; Rajesh, K.S.; Devakumar, K.; Shareefa, M.
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    Morphological and molecular characterization of a large fruited unique coconut accession from Vaibhavwadi, Maharashtra, India
    (2013) Niral, V.; Devakumar, K.; Umamaheswari, T.S.; Naganeeswaran, S.; Nair, R.V.; Jerard, B.A.
    The morphological and molecular characterization of a large fruited coconut population was undertaken using twentythree morphological traits, six tender nut traits and eight fruit component traits. Fruit component analysis of the nuts of this accession indicated that they have low husk to nut weight ratio typical of the Niu vai type cultivated in South East Asia. The microsatellite analysis indicated that Vaibhavwadi coconut population (MAHT) is generally close to the South East Asian coconut accessions and has proximity with dwarf accessions in the conserved germplasm of India. Though, genetic assignment test did not identify this accession specifically with any particular cultivar in the microsatellite database, the probable origin of this type could be identified as Borneo Tall (60% similarity) a cultivar which is known to produce large coconuts. It is suggested to conserve the MAHT in the National Coconut Gene Bank of India for its utilization in the breeding programme.
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    Observations on syncytial nuclei development in a mutant endosperm bearing coconut tree
    (Indian Society for Plantation Crops, 2008) Devakumar, K.; Damodaran, V.K.; Prabakaran, J.
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    Optimization of DNA amplification fingerprinting parameters in coconut (Cocos nucifera L.)
    (2004-12) Manimekalai, R.; Jeya Dev, K.; Anuradha Upadhyay; Devakumar, K.; Rajesh, M.K.; Parthasarathy, V.A.; Rajagopal, V.; Kumaran, P.M.
    DNA Amplification Fingerprinting (DAF) is a simple and powerful technique for genome analysis. It is being employed in various applications in a number of crops. For obtaining reproducible results from DAF technique, optimization of PCR parameters was done. 20 ng (2 ng/ µl) template DNA, 15 µM primer, 250 µM each of dNTPs, 2 U (0.2 U/µl) Taq polymerase, 4 mM MgCl2, and annealing temperature of 55 "C, with standard silver staining protocol gave good amplification with reproducibility.S ubsequently these results will be used in tagging resistance genes for root (wilt) disease in coconut. The effect of GC content of primers was also discussed.
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    Syncytial nuclei formation and development in coconut fruits
    (2009-03) Devakumar, K.; Prabakaran, J.
    Coconut endosperm is unique because of its early liquid syncytial stages, which forms a hard matured kernal at later stages of fruit development. Many free floating, naked nuclei devoid of cell membrane could be observed in the liquid syncytium. Different types of morphologically distinct syncytial nuclei were observed during the course of coconut fruit development. In two months old coconut fruits, the syncytial nuclei of 10-20 μm size in diameter were formed from cytoplasmic aggregations. Two types of syncytial nuclei 20-40 μm and >60 μm in diameter suddenly appear in 3-month old fruits. These early stage synctial nuclei were present in less than 1000 nuclei/ml. The four-month old coconut fruits were characterized by the appearance of numerous 1-2 μm sized bodies which aggregate together in definite numbers forming a dense cluster around which nuclear membrane is synthesized to form syncytial nuclei of 10-30 μm in diameter. During the fifth month of coconut fruit development, several membranous spherical bodies seeded with few 1-2 μm actively moving bodies inside appear. These bodies continuously multiply and condense inside the spherical membrane leading to a dense syncytial nucleus. The syncytial nuclei at this stage are highly active and it merges with one another thus increasing in size to form syncytial nuclei of 40-60 μm in diameter. The individual syncytial nucleus then becomes highly compact and several such compact nuclei organize themselves into a sheet like structure and proceed to settle on the lower regions of the endothelial layer. The settled syncytial nuclei cellularize and grow along the entire endothelial surface which then hardens to form the matured kernel.