Fifty-six accessions involving five taxa of Nephelium (N. Iappaceum varieties lappaceum and pallens, N. hypoleucum, N. ramboutan-ake, and N. cuspidatum) were fingerprinted and evaluated for genetic diversity using isozyme polymorphism. All five taxa were polymorphic for most of the enzymes encoded by 10 putative loci. Number of alleles per locus ranged from three for Pgi-1 to nine for Pgi-2 with a total of 57 alleles. Thirty-eight accessions out of 56 possessed unique isozyme genotypes, indicating a high level of diversity in the collection. On average, 80% of the loci were polymorphic and the expected and observed heterozygosities were 0.374 and 0.373, respectively. The cluster analysis of the isozyme data revealed five distinct clusters representing the five taxa included in the study. Genetic differentiation within N. Iappaceum var. Iappaceum was evident from the cluster analysis. Isozyme data indicated that N. ramboutan-ake is the closest relative of N. Iappaceum var. Iappaceum, followed by N. hypoleucum, N. Iappaceum var. pallens, and N. cuspidatum. Interestingly, the varieties of N. Iappaceum exhibited genetic divergence far beyond that of the congenerics, N. hypoleucum and N. ramboutan-ake and may require a taxonomic revision.
K.M. Aradhva, F. Zee, and R.M. Manshardt
F. Zee, K.M. Aradhya, and R.M. Manshardt
A genetic diversity analysis involving 49 Iychee (Litchi chinensis Sonn.) accessions using eight enzyme systems encoding 12 loci (Idh-1, Idh-2, Mdh-2, Per-1, Pgi-2, Pgm-1, Pgm-2, Skdh, Tpi-1, Tpi-2, Ugpp-1, and Ugpp-2) revealed moderate to high levels of genetic variability. Cluster analysis of the isozyme data from 40 genetically different accessions of the total 49 identified three groups at the 50% level of genetic similarity, the largest of which contained 32 of the 40 accessions distributed in three sub-groups. The groups including the three subgroups differed in frequency and composition of alleles at different loci. Polymorphism was observed in 77% of the loci, with an overall mean of 2.2 alleles per locus and an observed heterozygosity of 0.387. The unbiased genetic identities (I) between groups ranged from 0.809 to 0.937. Summing over all 11 polymorphic loci, 16% of gene diversity was due to differentiation between groups and 84% within groups. Comparison of isozyme fingerprints revealed that some accessions with identical names, particularly of `No mai tsz', `Kwai mi', and `Hak ip', possessed different isozyme genotypes, while other accessions with different names displayed identical isozyme genotypes. Isozyme fingerprinting will be useful in revealing and resolving questions of clonal identity, which are common in Iychee germplasm collections.
M.A Nagao, J.M Yoshimoto, E.B Ho-a, F. Zee, and S.C. Furutani
Extended storage studies were conducted on papaya, Carica papaya L. `Kapoho Solo', seeds to observe the effect of KNO3 preconditioning treatment when seeds were stored under ambient (25 C) and refrigerated (10 C) temperatures for 0, 2, 6, and 12 months. KN03 treated seeds maintained a constant germination percentage of 46.7 ± 2.7% throughout the 12 month period at both storage temperatures. Non-treated seeds stored at 25 C, however, had increased germination percentages (from 11 to 40% germination) after 2 months storage. Nontreated seeds stored at 10 C displayed a slower increase in germination percentages. The beneficial effects of KNO3 preconditioning treatments over nontreated seeds is observed only when seeds are sown immediately or within 2 months of storage at 25 C.