ISOZYME VARIATION IN LYCHEE (LITCHI-CHINENSIS SONN)

A genetic diversity analysis involving 49 lychee (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 sub-groups differed markedly both in frequency and composition of alleles at different loci. On average, 77% of the loci were polymorphic 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 between Groups 1b and 2 to 0.937 between Groups 1b and 1c. Group 2 has diverged from the other groups with an average genetic identity of 0.821. Summing over all 11 polymorphic loci, 16% of gene diversity was due to differentiation between groups and 84% to that within groups. Comparison of isozyme fingerprints revealed that some accessions identically named, such as 'No mai tsz', 'Kwai mi', and 'Hak ip', possessed different isozyme genotypes, whereas some others with different names displayed identical isozyme genotypes.