Browsing by Author "Thomas, R.J."

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    Analysis of genetic diversity in coconut and its conservation in root (wilt) disease affected areas of Kerala: A community participatory approach
    (2013) Thomas, R.J.; Rajesh, M.K.; Kalavati, S.; Krishnakumar, V.; George, D.J.; Jose, M.; Nair, R.V.
    Root (wilt) disease is a major constraint to coconut production in Kerala State. Conserving ecotypes with resistance or tolerance to the disease on a community basis is essential to sustain coconut production in the root (wilt) disease prevalent areas. Three communities viz., Pathiyoor and Devikulangara (Alappuzha District) and Thodiyoor (Kollam District) were selected and a survey was conducted with the participation of stakeholders, to characterize the local coconut ecotypes. Six ecotypes comprising of four talls and two dwarfs were identified and morphological data revealed that the local Jappanan ecotype closely resembled Evoor Green Tall ecotype. Simple Sequence Repeat (SSR) analysis in 90 selected coconut palms representing the six ecotypes using 14 markers indicated that the observed heterozygosity was higher in tall ecotypes (0.179-0.365) compared to the dwarfs (0.03-0.07). Lower values for observed heterozygosity compared to the expected heterozygosity in tall ecotypes are indications of genetic basis for disease resistance observed in diseasefree mother palms. Molecular characterization helped in identifying diverse coconut ecotypes having application in production of vigorous hybrids. In the dendrogram constructed using nut character data, three of the tall ecotypes (Green Tall, Brown Tall and Brick Red Tall) clustered together whereas Jappanan clustered separately. Mantel s correlation test using the ZT software revealed significant correlation (0.96) between the SSR data and morphological data.
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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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    Coconut varieties resistant to root (wilt) disease
    (2006-10) Nair, R.V.; Thomas, R.J.; Sunil A. Nair
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    Community Based Adoption of Intercropping in Coconut Based Farming Systems of Kerala with Special Reference to Tuber Crops
    (2013) Kalavathi, S.; Krishnakumar, V.; Thomas, R.J.; George V. Thomas; Anithakumari, P.
    Tuber crops are highly suitable for intercropping in coconut gardens at all growth stages. Hence these crops were included as the major intercrops for enhancing the livelihood security of coconut farmers under two projects funded by International Fund for Agricultural Development (IFAD)/The Coconut Genetic Resources Network (COGENT) and National Bank for Agriculture and Rural Development (NABARD) operated through Community Based Organizations (CBOs) under the aegis of Central Plantation Crops Research Institute (CPCRI). The projects were implemented in four coconut communities,Thekkekkara (under NABARD), Pathiyoor, and Devikulangara of Alappuzha District and Thodiyoor of Kollam District of Kerala (IFAD). Data related to area under intercrops, extent of adoption, income derived from the intercrops and the utilization pattern were recorded before and after the project using a standardized questionnaire template during 2005-2012 period. Data collection was done through personal interview with 609 CBO members and the data were coded and analysed using SPSS. All the four coconut communities indicated significant increase in the area and percentage of holdings under tuber crops and income from tuber crops alone as well as other short duration intercrops in general over the project period. The overall data for all the four communities revealed 3.7 fold increase in area under tuber crops alone and 29% increase in the holdings under adoption of tuber crops, whereas it was 2.2 fold and 24% in the case of intercrops in general. The share of income from tuber crops to total intercrop income increased from 49 to 60% in Thekkekkara, while that of the other three communities in general remained the same (72%) over the project period. The pre and post utilization pattern in terms of the value of product revealed increase in all categories- sold, consumed, supplied in kind and seed material- for tubers alone and intercrops together in all the four communities. In general, the area, production as well as income from tuber crops showed significant improvements through community based adoption. The proportion of tuber crops consumed was much higher (more than 60% of the total production) in Thekkekkara, while more than 50% of the total production was sold in the other areas. The results thus highlight the scope of intensifying the cultivation of tuber crops as food and cash crops to enhance the livelihood security of the coconut farmers.
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    Comparative transcriptome profiling of healthy and diseased Chowghat Green Dwarf coconut palms from root (wilt) disease hot spots
    (2018) Rajesh, M.K.; Rachana, K.E.; Kulkarni, K.; Sahu, B.B.; Thomas, R.J.; Anitha Karun
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    A cost-effective ground pollination system for hybridization in tall coconut palms
    (2018-03) Deva Kumar, K.; Arumuganathan, T.; Thomas, R.J.; Niral, V.; Anitha Karun; Chowdappa, P.
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    Development of varieties of coconut (Cocos nucifera L) resistant/tolerant to root(wilt) disease
    (2004-12) Nair, R.V.; Jacob, P.M.; Thomas, R.J.; Sasikala, M.
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    Diversification for Livelyhood Security:Experiences from Major Coconut Growing Countries
    (2012) Kalavathi, S.; Erlene Manohar; Peyanoot Naka; Vo Van Long; Krishnakumar, V.; Thomas, R.J.; George V. Thomas; Maria Luz George
    This paper presents the success of community based organizations in achieving sustainability in marginal coconut holdings through diversification of crops and enterprises along with conservation of local varieties.The project was implemented in 19 communities of 10 coconut growing countries and findings from four major coconut growing countries, which had significant project outcome- India, Philippines, Thailand and Vietnam -are discussed in the present paper.All the four major coconut growing countries recorded a significant difference in total household income over the project period.Among the four countries,India and Philippines had a significant difference in mean income derived from intercrops,India and Thailand for livestock integration and India and Vietnam for off-farm activities. Herfindahl index for indicating economic diversity of households revealed a significant diversification of income for India as well as the overall data for the four countries. A higher level of education and more available land also positively influenced total income.In general, improvements in income were better with bigger-sized farms and households, with male household heads.The overall data revealed significant improvement in food and nutritional security with clearest impacts in India and Philippines due to project efforts. Participation of women in trainings and interventions was the highest in India, followed by Thailand.
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    Ecological Bio-engineering in Coconut Ecosystem to deter pests
    (2018-10) Josephrajkumar, A.; Chandrika Mohan; Thomas, R.J.; Krishnakumar, V.
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    First record of Asian grey weevil (Myllocerus undatus) on coconut from Kerala, India
    (2010) Josephrajkumar, A.; Rajan, P.; Chandrika Mohan; Thomas, R.J.
    The occurrence of Asian grey weevil Myllocerus undatus (Curculionidae: Coleoptera) damaging coconut (Cocos nucifera L.) seedlings is reported for the first time from Kerala, India. A mild to moderate level of infestation damaging 5–10% leaf lamina of un-split leaves with a typical notching-like symptom along the leaf margins is noticed on the majority of the coconut seedlings belonging to different coconut varieties, viz., ‘Chowghat Orange Dwarf’, ‘Chowghat Green Dwarf’, ‘Malayan Green Dwarf’, ‘West Coast Tall’ and Dwarf x Tall hybrids. M. undatus has not been reported as a destructive pest on any of the crops from India and is considered to be a pest of quarantine significance. Adult weevils have a characteristic tri-spined hind femur and elytra strongly angled broader than the prothorax.
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    Genetic purity assessment of D x T hybrids in coconut with SSR markers
    (2012) Rajesh, M.K.; Thomas, R.J.; Rijith, J.; Shareefa, M.; Jacob, P.M.
    Assessment of genetic purity in coconut hybrids was done using molecular markers. A set of 50 hyperpolymorphic coconut SSR markers were utilized to characterize parental lines Chowghat Green Dwarf (CGD) and West Coast Tall (WCT) used for hybrid coconut production. A panel of 17 informative SSR markers capable of distinguishing these parental lines was identified and these markers were utilized in DxT hybrid seedling purity assessments in coconut nurseries.
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    Growth and vigour of coconut seedlings raised from eriophyid mite (Aceria guerreronis Keifer) infested seed nuts
    (2004-12) Thomas, R.J.; Nair, R.V.; Nair, C.P.R.; Nampoothiri, C.K.; Cherian Mathews
    Considering the wide spread apprehension regarding suitability of mite infested seed nuts for raising seedlings, a study was undertaken to evaluate the growth and vigour of coconut seedlings raised from mite-infested seed nuts. The maximum values for all the growth characters were recorded in seedlings raised from grade-3 infested seed nuts. However, higher percentage of vigorous seedlings (with Z score of 22 and above) was obtained in seedlings raised from uninfested I grade-0 nuts. The faster germination recorded in grade-3 infested nuts and their subsequent better establishment may be the reasons for the superior performance of seedlings raised. On the basis of the present investigation, it is recommended that mite infested seed nuts should be sorted into lots. depending on severity of infestation. and nursery raised separately for each lot so that competition between seedlings, raised from different grades of mite infested nuts, can be minimized. This will help in obtaining more vigorous seedlings from the mite infested seed nuts.
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    Incidence of root (wilt) disease in various cross combinations of west coast tall variety of coconut
    (2003) Nair, R.V.; Jacob, P.M.; Rajesh, M.G.; Thomas, R.J.
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    Kalparaksha, a new coconut variety, resistant to root (wilt) disease
    (2009-05) Nair, R.V.; Thomas, R.J.; Jacob, P.M.; George V. Thomas
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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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    New distributional record of buff coconut mealybug (Nipaecoccus nipae) in Kerala, India
    (2012-08) Josephrajkumar, A.; Rajan, P.; Chandrika Mohan; Thomas, R.J.
    The buff coconut mealybug, Nipaecoccus nipae (Maskell) (Pseudococcidae: Hemiptera), was recorded on tender feeder roots of coconut seedlings at Kayamkulam, Kerala, India. N. nipae was not located on any other arboreal parts of palm including foliage. This is a new distributional record of the pest in Kerala, South India. The concealed nature of the pest on underground feeder roots of coconut seedlings warrants thorough examination at the seedling distribution point of coconut seedlings in order to prevent the spread of this pest to other free zones of the country. Re-emergence of the pest is reported in India after a time gap of 100 years.
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    Participatory Approaches for Conserving Coconut Genetic Resources to Sustain Production and Livelihood Security in Coconut Growing Communities
    (2009-02) Thomas, R.J.; Rajesh, M.K.; Kalavati, S.; Krishnakumar, V.; George, D.J.; Jose, M.; Nair, R.V.
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    Performance of CGD x WCT Hybrid in the Coconut root (wilt) disease prevalent tract
    (2006) Nair, R.V.; Jacob, P.M.; Thomas, R.J.; Seema P. Pillai; Mathew, C.
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    Raising coconut nursery for the root (wilt) disease prevalent tracts
    (2008-07) Thomas, R.J.; George, D.J.; Nair, S.A.; Sairam, C.V.; Jacob, P.M.