Isozyme variation and growth performance in 16 provenances of African Faidherbia albida (Del.) A. Chev. in Kenya

Sixteen provenances representing the African distribution range Faidherbia albida were used to determine its genetic diversity, based on nursery seedling characteristics, juvenile field trees and isozyme assay. Eastern and Southern Africa had taller seedlings with bigger collar diameter than the Western Africa provenances. Rama from East Africa was peculiarly closer to West African provenances. West African provenances had comparatively fewest branches per tree. East African provenances had intermediate collar diameter values, Overall, East and South African provenances were statistically similar (P=0.05) while the West African formed a distinct group. An average, 2.6 alleles per locus were detected and 43.2% of the loci were polymorphic at 95%, criterion. The average Nei's (1978) unbiased expected heterozygosity was 0.140. Southern Africa had least genetic diversity relative to West and East African provenances. The significantly higher correlation between genetic factor and latitude conformed to the low verses high isozyme diversity within Southern African and West African provenances respectively, Isozyme variability was negatively correlated to growth rate at both regional and species levels, suggesting that a high level of genetic diversity may not be a good indicator for superior growth in this species and therefore not a prerequisite for the species domestication. Both morphological and isozyme analysis showed an overall clinical variation in F Albida distribution and divided the species into two distinct ecological races comprising the Western versus Southern African with Eastern African having intermediate values. The Ethiopian provenances shared both the Western and Southern African characteristics strengthening the theory that Ethiopia is the possible species center of origin.