Microsatellite markers development and molecular fingerprinting of cashew cultivars

Cashew (Anacardium occidentale L.) is a widely cultivated tree with great economic significance. In cashew, several elite cultivars have been developed for commercial cultivation, which form the underpinning for the cashew-based industries and the several billion-dollar world trade. However, frequently the genetic purity of the planting material is not maintained, resulting in great economic losses. Therefore, there is a need to develop a reliable method for the identification of cultivars to avoid economic losses to the cultivators and the protection of cultivars by the breeders.

In this study, 35 new microsatellite/simple sequence repeat (SSR) markers were developed, and a set of 20 highly polymorphic and reproducible markers were used for DNA fingerprinting and genetic diversity analysis in 32 cashew cultivars. The polymorphic information content (PIC) of newly developed markers varied from 0.19 to 0.67, with an average of 0.44. The probability of identifying any two genotypes with identical fingerprints using the 20 SSR markers used for fingerprinting here in cashew cultivars was less than 2.8 × 10^-11. Of the set of 20 markers, eight were sufficient for uniquely fingerprinting all the cultivars. Genetic diversity analysis by the neighbor-joining (NJ) method grouped 32 cultivars into three main clusters, and the grouping had no relationship to the geographic regions or the pedigree.

The findings of this study are useful for the conservation and protection of cultivars under the PVP Act for ensuring the trading of quality planting material and are also useful for cashew breeding programs.