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 (R) 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.

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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.

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Immature inflorescence with outer spathe length of 5.5 cm size collected from West Coast Tall cultivar of coconut was used as the explant and rachillae bits were inoculated in Y3 media supplemented with 2, 4-D (1 mg L-1). The cultures were incubated in dark for eight months and sub-cultured into the same media at monthly interval. The white shoot like outgrowths formed were sub cultured to ½ MS media fortified with 1 mg L-1 each of NAA and BAP and subsequently transferred to light condition. After three months, the emerging shoot likestructure was transferred to Y3 media fortified with NAA and BAP. Upon developing 3 - 4 leaves, the cultures were transferred to rooting media and root initiation was observed after two months. The transition of vegetative shoot to reproductive state was accompanied by some morphological changes including rapid emergence of long and thin leaves followed by emergence of pearly white inflorescence. Unlike normal inflorescence, the inflorescence emerged was terminal and was devoid of spathe. Prolonged subculture in the same media might have resulted in pH variation and subsequent reduction in organic and inorganicconstituents of the media. The chemical stress experienced by the plantlet might have induced in vitro flowering.