Sixteen SSR markers were used to identify genetic relationships of 43 coconut accessions conserved ex-situ in field gene banks of the Coconut Research Institute of Sri Lanka (CRISL). The 16 SSR markers clearly unveiled the genetic relationships of Sri Lankan coconut populations. Gene diversity and polymorphism information content (PIC) were relatively higher in the common 'tall' coconut and Pacific tall coconut than in autogamous dwarf form of coconut. The SSR assessment unveiled the genetic lineages based on evolutionary mechanisms signifying the narrow genetic base of coconut germplasm, with most of the diversity confining to 'tall' coconut. The main genetically different coconut groups identified were 'tall', 'San Ramon and alike' and 'dwarf'. These have already been utilised in coconut improvement programmes and the study emphasizes the need for enrichment of the gene pool by exotic introductions. The overall results also supports the hypothesis that coconut disseminated from it's center/s of origin in far east to Indo Atlantic regions via America.

Carica papaya L. exhibits monoecious and dioecious plants that usually take six months for phenotypic manifestation. Nursery culling aided by sex-specific DNA markers was envisaged to alleviate the unnecessary cost incurred by farmers for maintaining unproductive male plants that contribute to 40-50% of the population. The mechanism of sex determination in papaya has been described as a tri-allelic single gene system with alleles, M 1 -dominant for maleness, M 2 -dominant for hermaphrodism and m-recessive for femaleness with diploid zygotes; M 1 M 1 , M 2 M 2 and M 1 M 2 being inviable. Bulked DNA samples of male, female and hermaphrodite plants were amplified by Random Amplified Polymorphic DNA-Polymerase Chain Reaction (RAPD-PCR) using 100 random primers. Twenty of most promising of these were analyzed among individual sex types. Two sex-specific fragments, OPC09-1.7 and OPE03-0.4 were associated with maleness and hermaphrodism. The segregation of these two markers was analyzed in the F 1 population obtained by selfpollinating a hermaphrodite plant. A linkage was detected between the RAPD markers, OPC09-1.7 and OPE03-0.4 and the male and hermaphrodite sex of papaya plants. These sex-specific RAPD fragments were cloned and sequenced for converting them to more authentic SCAR markers. The Southern blot hybridization of RAPD-PCR products obtained by amplification of female, male and hermaphrodite papaya DNA amplified by OPC09 primer using radio labeled recombinant plasmid detected a polymorphic fragment in male and hermaphrodite papaya sex types. The nucleotide sequence of OPC09-1.7 fragment showed the possibility of developing more authentic SCAR markers to enhance the accurate sex determination of Carica papaya at the nursery stage.

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Accurate estimation ofgenetic distances between and within species is vital in

Different combinations of river sand, cow dung and coir dust were compared with the conventional polybag mixtures to study whether seed germination would be affected by the substitution of top soil with river sand. The seed nut germination at 20 weeks was significantly reduced in the sand substituted media, but the difference disappered by 24 weeks from laying. The lower rate of germination was also associated with a reduction of seedling vigour at 30 weeks, probably due to poor seedling nutrition. River sand could be used as an alternative to top soil, provided the nutritive status of the sand is improved and refinements are made to decrease its rate of drying.