REGI JACOB THOMAS
@icar.gov,in
Principal Scientist, Division of Crop Improvement
Indian Council of Agricultural Research
Scopus Publications
Scopus Publications
Regi J. Thomas, M. Shareefa, C. K. Nampoothiri, and Jeena Mathew
Diva Enterprises Private Limited
Regi J. Thomas, M. Shareefa, H. Harsha, and Anitha Karun
Update Publishing House
Coconuts with various traits are available in different coconut growing countries. The pink husk is one such trait that has already been reported in coconut. There is a demand for tender nut water from pink husked types of coconut to treat hepatitis by traditional medicinal practitioners. Present studies were carried out to characterize pink husked types identified in Guam Tall variety of coconut. There were no morphological differences with respect to the nut characters between pink and non-pink husked types. Biochemical characterization of pink husked types revealed significantly higher total phenol content in the tender nut water of pink husked types than normal husked types. A significantly higher protein content of 86 mg 100 mL-1 was noted in pink husked type, compared to normal husked type with 58.7 mg 100 mL-1. Higher free radical scavenging activity based on DPPH assay with pink husked type was recorded with an IC50 value of 266.7 compared to normal type with an IC50 value of 358. Similarly, phosphomolybdate assay also revealed higher scavenging activity of pink husked type based on the IC50 value of 415.2 compared to 637.9 observed in normal husked type. Anthocyanin content of 25.98 mg 100g-1 fresh weight was noted in the exocarp of pink husked types, and it was negligible in normal husked type. These results justify the use of pink husked coconuts in various traditional medicines. There is tremendous potential for exploiting pink husked types of coconut in the pharmaceutical industry.
S. Indhuja, , M. Babu, A. Gupta, M. Gopal, J. Mathew, R.J. Thomas, A.A. Haris, V. Krishnakumar, ,et al.
Triveni Enterprises
Aim: Isolation, screening and characterization of beneficial rhizosphere bacteria associated with healthy (field-resistant) coconut palms in root (wilt) disease endemic hotspot areas of Kerala. Methodology: One hundred and ten rhizobacterial isolates associated with healthy coconut palms of root (wilt) diseased tract of Kerala were isolated and screened in-vitro for IAA production and solubilization of fixed forms of mineral nutrients. Seven isolates showing multiple phytobeneficial properties were characterized and the selected isolate was tested for its biopriming effect on maize. Results: Of the total isolates screened, 54 isolates produced IAA. Among the nutrient solubilizers, silicate solubilizers (57%) and phosphate solubilizers (48%) dominated. Of the seven isolates with multiple phytobeneficial properties, five rhizobacterial isolates belonged to Enterobacteriaceae family including three Enterobacter spp. The isolate T4HFB9 belonged to Acinetobacter sp. The green fluorescent Pseudomonas isolate K3HPSB2, showed 99% sequence similarity with Pseudomonas migulae. Seed biopriming of maize with Pseudomonas sp. strain K3HPSB2 recorded significant increase in germination percentage and seedling vigour index over untreated control. Interpretation: Disease-resistant coconut palms in RWD endemic tracts host a good proportion of phytobeneficial rhizosphere bacteria,with demonstrable multiple plant growth promoting traits. Multi-nutrient solubilizing Pseudomonas sp. with bioinoculant prospects has been selected for further studies on bio-priming for palm health management in RWD endemic tracts.
K. Devakumar, Regi Jacob Thomas, and Anitha Karun
Update Publishing House
Large-scale production of hybrid seed nuts of coconut is necessary to match the high demand for hybrid seedlings. But in major coconut producing states such as Kerala, Karnataka and Goa hybridisation is carried suspended during monsoon season and out effectively only during dry season for a period of six months from November to May. Some of the reasons attributed to the stoppage of pollination work during monsoon are the slippage of the trunk while climbing, problems in male flower collection and wetting of the pollination bags during heavy rains. Technological developments in coconut sector viz., the invention of coconut climbing devices and cryopreservation techniques have contributed to safe climbing and pollen storage for utilisation during off-seasons, respectively. However, the wetting of the pollination bag used for hybridization remains a problem. We report the development and successful initial testing of a durable raincoat for the pollination bag so that coconut pollination can be carried out throughout the year in heavy monsoon areas. This reusable raincoat is integrated with the ground pollination unit and can be fitted easily on the pollination bag, and it ensures complete dryness of the pollination bag. Only one climbing per tree is required for emasculation, bagging and raincoat fitting on a single inflorescence. The raincoat has provisions for suspending a pollen delivery tube and pollen dusting and bag removal can be done from the ground. The durable raincoat cover for the pollination bags has resulted in a fruit setting of 22.5-41.3 per cent.
Chandrika Perera, H. D. Dharshani Bandupriya, Regi J. Thomas, and Roland Bourdeix
Springer International Publishing
The introduction of molecular markers in the latter part of the twentieth century denoted a major advancement in the research on plant genetics. Molecular markers have become highly advantageous to help overcome certain inherent difficulties associated with the genetic improvement of perennial crops such as coconut. Starting from the middle of the 1990s, considerable progress has been achieved in the genetic diversity analysis of coconut. The early attempts of molecular research on coconut used the common molecular marker systems of the time, such as randomly amplified polymorphic DNA and amplified fragment length polymorphism. Later, the generation of coconut-specific DNA markers and the adoption of high-throughput systems have paved the way for an acceleration, with greater accuracy, in using molecular markers for diversity studies in coconut. Molecular markers have also been used in the development of linkage maps and the identification of quantitative trait loci (QTL) in coconut. The research using molecular markers has been used, and will be further useful, in formulating and refining the further collection and conservation of coconut germplasm, the management of genebanks, identification of duplicates, and determining the strategies for rejuvenation of the existing field genebanks. The data can further be used in the parental selection in the coconut breeding programmes aimed at combining the desirable characters from diverse parents into novel cultivars. The availability of high-throughput marker systems will increase the accuracy and precision of genetic and QTL mapping via linkage analysis. Further, association studies which facilitate the use of existing populations in QTL mapping will be an important tool in moving towards marker-assisted selection of coconuts for desirable traits to ensure sustainability of the coconut industry.
M. Shareefa, Regi J. Thomas, J. S. Sreelekshmi, M. K. Rajesh, and Anitha Karun
Current Science Association
Clonal propagation of elite, disease-free coconut
palms is a promising technique for producing uniform
planting material with high yield and disease
resistance. Over the past few decades cloning of coconut
has been attempted in a number of laboratories
worldwide; however, success has been limited. In the
present study, immature inflorescences of 2–12 cm
size were collected from West Coast Tall variety and
the rachilla segments were cultured on four different
media combinations in dark condition. White
translucent outgrowths were maximum in Y3 medium
supplemented with 4.54 μM 2,4-dichlorophenoxyacetic
acid (92%) followed by medium 72 with 41.4 μM
picloram, 61.8 μM putrescine and 4.54 μM thidiazuron
(TDZ) (87%). After eight weeks in dark, shoot-like
outgrowth was noticed more in Y3 III (65%) followed
by Y3 I. After eight months dark incubation, the
cultures were transferred to 1/2 Murashige and Skoog
(MS) with two hormone combinations and high
frequency of multiple shoot formation was noticed in
1/2 MS with 5.37 μM naphthalene acetic acid (NAA)
and 4.44 μM 6-benzylaminopurine (BAP). Maximum
shoot development was observed Y3 medium fortified
with 5 μM 2-isopentenyl adenine (2ip) and 5 μM BAP.
The individual shoots after development of 3–4 leaves
were transferred to 1/2 Y3 medium supplemented
with 5.37 μM NAA and 24.6 μM indole-3-butyric acid
(IBA), and root initiation was observed in 39.28%
plantlets. Start codon targeted (SCoT) profiling based
on banding pattern of PCR-amplified products
confirmed the clonal fidelity of in vitro regenerated
coconut plantlets. The study indicates the possibility
of developing an in vitro regeneration protocol for
coconut using immature inflorescence explants.
Regi J. Thomas, M. Shareefa, and R. V. Nair
Springer Singapore
Host plant resistance offers long-term and sustainable solution in biotic stress management in coconut. Among the diseases affecting coconut, phytoplasmal diseases reported from various countries are a major concern. Furthermore, bud rot, basal stem rot and stem bleeding are also very serious diseases limiting coconut production. Replanting with resistant varieties will go a long way in mitigating the adverse effects of these biotic factors, especially in cases where effective control measures are not available. The best and viable option in the future will be the management of coconut diseases mostly relying on integrated management practices centred on the exploitation of sources of disease resistance. Anticipating a rapid advancement in density and damage by sucking pests in the present era of climate change, efforts should be oriented to develop coconut varieties that can resist/tolerate coreid bug, eriophyid mite and emerging invasive pests as well. Besides, the focus to breed coconut varieties with resistance to red palm weevil, the most dreaded pest of coconut, should continue. It would be appropriate if the breeding programme in each coconut-growing country is fine-tuned to develop resistant varieties to combat pests/diseases of regional importance fully utilising the vast genetic resources available in those countries.
M. Shareefa, Regi J. Thomas, and C. K. Nampoothiri
Diva Enterprises Private Limited
M. K. Rajesh, K. E. Rachana, K. Kulkarni, B. B. Sahu, R. J. Thomas, and A. Karun
Springer Science and Business Media LLC
Understanding the molecular basis of host-pathogen interactions is imperative for devising disease management strategies. The root (wilt) disease is the foremost debilitating disease threatening coconut production in India. To explore the molecular mechanisms involved in compatible and incompatible interactions, global transcriptome profiling of leaves of healthy and diseased Chowghat Green Dwarf (CGD) palms was conducted. RNA-Seq analysis generated more than 190 million 100 bp reads from both healthy and diseased samples. Assembled transcriptome yielded 59,282 transcripts with a median length of 987 bp. BLASTX annotation of transcriptome resulted in 39,665 transcripts getting annotated from Uniprot and date palm proteome database. Differential gene expression profiling analysis revealed 2718 transcripts to be up- or down- regulated in the diseased palms in comparison to healthy control at a fold change of 2 and above with a p value <=0.05. The differentially expressed transcripts could be categorized into pathways which included cell wall biogenesis, primary and secondary metabolism, plant-pathogen interaction, cellular transport, hormone biosynthesis and signaling. Validation by quantitative real time PCR (RT-qPCR) of a set of arbitrarily selected genes, both up-regulated and down-regulated, established a comparable pattern as observed by RNA-Seq analysis. Overall, the resources generated in this study provide an in-depth analysis and new insights into the interaction of coconut palms with the root (wilt) disease pathogen.
K. Deva Kumar, T. Arumuganathan, R. J. Thomas, V. Niral, Anitha Karun, and P. Chowdappa
Current Science Association
Large-scale production of hybrid seed nuts of commercially cultivated palms such as coconut, arecanut, oil palm and date palm is of prime importance due to the high demand for hybrid nuts and their role in augmenting the production of these crops. However, commercial production of hybrid nuts in these crops is impeded by various factors such as height of the palms, cost and availability of labour, low percentage of fruit-setting, seasonal influences like monsoon rains, etc. We report here the development and use of a simple, viable, cost-effective and labour-saving device for pollinating tall palms from ground-level, which is ideal for large-scale commercial production of coconut hybrids, even by farmers. At least four climbs per coconut palm can be saved by this method during the hybridization process. This simple method can enhance the availability of hybrid seedlings at a cheaper rate to coconut farmers. This method of pollination developed for coconut, can easily be adapted to other commercially important palms depending on the bunch morphology.
B. A. Jerard, M. K. Rajesh, Regi Jacob Thomas, V. Niral, and K. Samsudeen
Springer Science and Business Media LLC
Oceanic island ecosystems present immense opportunities for the study of species evolution due to their isolated geographical nature and presence of highly rich species diversity. Assessment of genetic diversity and population structure of four distinct coconut groups, viz. Giant, Ordinary, Micro and Mini Micro types of Minicoy Island, India, was carried out using morphological traits and microsatellite markers. The morphological data set, analysed using principal component analysis, revealed high genetic variability for fruit component traits. The occurrence of Laccadive Mini Micro Tall palms, bearing the smallest coconuts in the world, was observed in the island. The nuts of these palms had a low copra content of 5 g/nut, but high oil content of around 73%. A total of 70 alleles were detected among the four distinct coconut groups of the Island using 19 polymorphic microsatellite markers with a mean of 3.68 alleles per locus. The fixation index ranged from 0.153 to 0.424 indicating highly variable levels of inbreeding in these populations. Pair-wise population matrix formed by Nei’s genetic identity showed that Laccadive Mini Micro Tall was genetically distinct from all other groups. The study revealed the presence of rich coconut diversity in islands and highlights the importance of exploration and conservation of such diverse accessions with rare genes for utilizing them in crop improvement.
R.J. Thomas, M. Shareefa, R.V. Nair, P.M. Jacob, M. Sasikala, M.K. Rajesh, and A. Karun
International Society for Horticultural Science (ISHS)
Raman V. Nair, B. A. Jerard, and Regi J. Thomas
Springer International Publishing
Cocos nucifera L. is a perennial multipurpose palm grown widely in the humid tropics. It provides nutritious food and refreshing drink, edible oil and non-edible uses, fiber of commercial value, shells for fuel and industrial uses, timber and a variety of miscellaneous products for domestic and industrial uses. It is grown mainly in coastal areas and island ecosystems sustaining the livelihood of people and protecting the environment. There are conflicting theories regarding the origin and domestication of coconut. Coconut populations worldwide have been classified into two major groups: the Pacific group with five sub-groups (Southeast Asia, Melanesia, Micronesia, Polynesia and the Pacific coast of Central and South America), and the Indo-Atlantic group. The genetic resources in coconut are widely exploited through selection, hybridization for a number of desirable traits and have resulted in the development of many varieties. Breeding efforts are mostly confined to conventional approaches such as mass selection and hybridization, besides attempts to use individual palm selection for novel traits. Its perennial nature, heterozygosity, long juvenile phase and lack of technologies for mass propagation of palms with targeted traits are the challenges in breeding efforts. This chapter covers conventional breeding approaches such as mass selection and hybridization, information on varietal groups, identified genetic resources, breeding methods and techniques, current status and future strategies of coconut breeding in India.
Kaitheri Edathil Rachana, Sudalaimuthu Asari Naganeeswaran, Thayale Purayil Fayas, Regi Jacob Thomas, and Muliyar Krishna Rajesh
Walter de Gruyter GmbH
AbstractCoconut palms are highly susceptible to diseases caused by different pathogens, and replanting with resistant varieties is the best way to manage them. Obtaining a collection of resistance gene analogues (RGAs) is an effective strategy to identify genomic regions linked to disease resistance. We have successfully used a comparative genomics approach to amplify putative RGAs from the coconut root (wilt) disease resistant cultivar Chowghat Green Dwarf (CGD) by using primers designed based on conserved motifs of the NBS-LRR domain of the date palm. The amplified sequences were cloned, sequenced and characterized. The coconut RGAs had high identity to monocot NBS-LRRs. A complete structural analysis and 3-D modeling of the NBS domain of coconut RGA was also undertaken. Real-time quantitative polymerase chain reaction analysis indicated that the isolated coconut NBS-LRR class RGAs was expressed more in root (wilt) disease resistant genotypes than in susceptible ones. This study would provide a base for future efforts to map disease resistant traits in coconut.
Muliyar Krishna RAJESH, Kaitheri Edathil RACHANA, Sudalaimuthu Asari NAGANEESWARAN, Rahman SHAFEEQ, Regi Jacob THOMAS, Mohammed SHAREEFA, Babu MERIN, and Karun ANITHA
The Scientific and Technological Research Council of Turkey (TUBITAK-ULAKBIM)
Coconut, an important crop of the tropics and subtropics, is susceptible to a variety of diseases and enhancing disease resistance has been the major goal of coconut breeding programs all over the world. Information on the presence and distribution of disease resistance ® genes, which play a primary role in the detection of pathogens and the initiation of specific plant defenses, is scarce in coconut. In this study, RNA-Seq was used to generate the transcriptome of leaf samples of coconut root (wilt) disease-resistant cultivar Chowghat Green Dwarf. Comprehensive bioinformatics analysis identified 243 resistance gene analog (RGA) sequences, comprising 6 classes of RGAs. Domain and conserved motif predictions of clusters were performed to analyze the architectural diversity. Phylogenetic analysis of deduced amino acid sequences revealed that coconut NBS-LRR type RGAs were classified into distinct groups based on the presence of TIR or CC motifs in the N-terminal regions. Furthermore, qRT-PCR analysis validated the expression of randomly selected NBS-LRR type RGAs. The results of this study provide a sequence resource for development of RGA-tagged markers in coconut, which would aid mapping of disease-resistant candidate genes. In addition, we hope that this study will provide a genomic framework for isolation of additional RGAs in coconut via comparative genomics and also contribute to the deciphering of mode of evolution of RGAs in Arecaceae.
Rajesh MK, Jerard BA, P Preethi, Regi Jacob Thomas, and Anitha Karun
FapUNIFESP (SciELO)
Coconut palms are classified into two major types, viz., 'talls' and 'dwarfs', which mainly differ in their pollination behavior of cross- and self-pollination, respectively. Due to this difference, getting true-to-type progenies of desirable tall and dwarf cultivars has always been a challenge. The conventional practice of selection of seedlings based solely on morphological traits often results in selection of out-crossed seedlings and undesirable off-types. In the present investigation, RAPD markers for the tall/dwarf trait were identified in coconut using a bulked DNA approach. Screening of tall and dwarf palm bulk DNA with 200 primers revealed a RAPD primer OPBA3 which was able to clearly differentiate both the tall and dwarf bulks. For validation, the primer was used to screen individual tall and dwarf coconut palms representing different geographic regions. The primer was also used to screen the parents and validate hybrids of Dwarf x Tall crosses.
R. J. Thomas, M. K. Rajesh, S. Kalavathi, V. Krishnakumar, D. J. George, M. Jose, and R. V. Nair
The Indian Society of Genetics and Plant Breeding
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.
M.K. Rajesh, B.A. Jerard, P. Preethi, Regi Jacob Thomas, T.P. Fayas, K.E. Rachana, and Anitha Karun
Elsevier BV
Abstract Coconut palms are classified into two major types, viz. ‘talls’ and ‘dwarfs’, based on plant stature. The selection of coconut seedlings in the nursery, presently relying solely on morphological markers, often results in selection of out-crossed seedlings. Hence, identification of molecular markers for distinguishing tall/dwarf character at an early stage of growth assumes importance. In the present investigation, a RAPD marker for tall-type palm trait was identified using a pooled DNA approach. Screening of tall and dwarf palm bulked DNA with 200 decamer primers revealed a primer OPA09, producing a unique band of around 260 bp exclusively in tall accessions. The primer was used for screening and validation in individual tall and dwarf coconut accessions representing different geographic regions. The band was present in all the tall accessions, but absent in the dwarfs. Furthermore, sequence characterized amplified region (SCAR) primers were designed from the unique RAPD amplicon. The primers produced a specific 260-bp amplicon in tall accessions, but not in dwarf accessions. The SCAR marker was utilized in assessing the purity of hybrid seedlings of D × T (Dwarf × Tall) cross. The results pave the way for ensuring genuineness/quality of hybrid seedlings of coconut.
A. Josephrajkumar, P. Rajan, Chandrika Mohan, and R. J. Thomas
Springer Science and Business Media LLC
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.
A. Josephrajkumar, P. Rajan, Chandrika Mohan, and R. J. Thomas
Springer Science and Business Media LLC
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.