Genetic structure and bottleneck studies at the malate dehydrogenase and phosphoglucoisomerase (Glucose-6-phosphate isomerase) gene loci of neem (Azadirachta indica)

Abstract

Genetic structure of the neem at the malate dehydrogenase and phosphoglucoisomerase (glucose-6-phosphate isomerase) gene loci was
studied in a total of 192 seedlings raised from seeds collected from eleven maternal plants. Both loci were polymorphic and the mean number of alleles per locus was 5.05 + 0.54. Mean observed was 0.902 + 1.4. Levene’s and Nei’s expected heterozygosities were 0.804 + 0.02 and 0.801 + 0.02, respectively. Wright’s fixation index Fis estimates were negative for all the six alleles for the Mdh locus while for the Pgi locus the estimate was positive for two of the alleles. Analysis of molecular variance (AMOVA) indicated that 17.8 per cent of the total genetic diversity resided among families. The results showed that there was low level of population structure in the neem sample studied at the Mdh and Pgi gene loci and that the 11 families approximate a single panmictic unit. A normal ‘L’ shaped distribution of mode-shift test and three heterozygote excess tests suggested that there was no recent bottleneck in the population of neem at the two enzyme gene loci.