Molecular Analysis of Intracultivar Polymorphism of ( Panchadarakalasa ) Mango by Microsatellite Markers

Abstract

Juicy mangoes (sucking type/rasaalu) are one of the most significant mango (Mangifera indica L.) businesses in Andhra Pradesh state, India. The mango orchardists cultivate a great number of juicy cultivars for which genetic homogeneity has never been demonstrated.'Panchadarakalasa' is one of the choicest juicy cultivars of mango in the state, where certain level of intracultivar variability in fruit morphology has been observed among trees. In this study, fruit and leaf samples of 16 trees of ‘Panchadarakalasa’ (PK Acc-l to PK Acc-16) spread over the three eco-geographical regions (Coastal Andhra, Rayalaseema and Telangana) of the state were collected during summer 2009, which were subjected to in-situ morphological and ex-situ microsatellite analysis, respectively to identify whether there is variability in the plants grown in the state. Characterization and evaluation of fruit samples based on 9 quantitative and 7 qualitative traits revealed phenotypic variations among accessions under study. Twenty out of 109 mango-specific microsatellite markers validated, were amplified. Of the 20 microsatellites amplified, only 4 were polymorphic with a total of 11 alleles ranging from 130 bp to 245 bp. The polymorphic information content of the polymorphic alleles ranged from 0.25-0.56, whereas the Jaccard’s similarity coefficient values ranged from 0.9-1.0. The pair-wise genetic dissimilarities ranged from 0.00-0.10 with a mean value of 0.05. Dendrogram based on unweighted pair group method of arithmetic means algorithm indicated that the accessions were not grouped as per geographic separation. Microsatellite analysis revealed smaller intracultivar variability of 10% in in-situ conditions and a genetic divergence between trees attesting that ‘Panchadarakalasa’ whatsoever cultivated throughout the state is not pure clone. The traditional nursery practices are likely to be responsible for the intracultivar polymorphism since the ‘Panchadarakalasa’ not propagated exclusively vegetatively. Highly polymorphic microsatellites like SSR-83, MngSSR-24 and MngSSR-26 were more useful in differentiating the ‘Panchadarakalasa’ accessions. The results generated with microsatellite markers will be helpful in intracultivar improvement as well as in the application of breeder rights in the country.