Molecular Characterization and Analysis of Geographical Differentiation of Indian Mango (Mangifera indica L.) Germplasm

A set of 241 mango landraces and commercial cultivars from 15 different regions of India were analyzed for microsatellite variability. 18 primer pairs selected for high polymorphism were used for the analysis. A total of 103 alleles with an average of 5.78 alleles per primer pair were scored in the cultivars analyzed. The pair-wise similarity coefficients for the cultivars ranged from 0.024 to 0.808 with an average of 0.258 indicating presence of high genetic diversity among the cultivars analyzed. Partitioning of total molecular variance among germplasm from 15 regions representing 8 groups based on geographic contiguity showed that among groups difference accounted for 1.91%, among populations within groups for 3.80%, among cultivars within population 57.87% and differences within individual cultivars accounted for 36.42% of the total variations. The F-ST value derived from these estimates was 0.019 indicating that the cultivars in the 8 major geographic groups were not strongly differentiated except Manipur of the North eastern region. The validity of synonyms and homonyms for cultivar names were investigated by analyzing cultivars bearing the same names but under cultivation in different regions. Results indicated presence of differences in molecular profiles for most cultivars analyzed. Analysis of molecular variance, low F-ST value, cluster analysis and high values for estimates of N-m indicated presence of substantial gene flow between the cultivars from different regions, possibly due to cultivar exchange followed by gene introgression by crossing and selection. These processes might have homogenized the population structure of mango cultivars in the country.