Genetic diversity and identification of interspecific hybrids of Anacardium species using microsatellites

Study of genetic diversity and interspecific hybridizations plays an imperative role in the genetic improvement of crop plants. Microsatellite or simple sequence repeats (SSRs) markers have been the marker of choice for many genetic studies in perennial tree crops. In this study, genetic diversity of 23 cashew (Anacardium occidentale L.) germplasm accessions with unique traits was carried out using the cashew SSR (CSSR) markers. Besides, true hybridity of the interspecific hybrids of A. occidentale and A. microcarpum Ducke was investigated. Eight of the 21 CSSRs screened in 10 diverse accessions were polymorphic and used for genetic diversity analysis in 23 accessions. Major allele frequency ranged from 0.50 to 0.98; gene diversity ranged from 0.10 to 0.50, and polymorphism information content (PIC) ranged from 0.10 to 0.38 for the surveyed SSR loci. Dendrogram analysis of 23 accessions formed two main clusters with two sub-clusters in each. Clustering of the accessions had no relationship with the geographic region of collection. In tree hybridizations, early screening methods are becoming indispensable to ascertain the true hybridity of progenies to save the costs and resources. For the first time, three CSSR markers that detect the true hybridity of interspecific hybrids of cashew and its wild relative A. microcarpum were identified. Hybrid purity index of the progenies in interspecific crosses varied from 67 to 100%. These three CSSR markers capable of distinguishing the two Anacardium species could be useful in evolutionary studies involving these species and their natural hybrids in the wilds.

Automated summary

Genetic diversity and interspecific hybridizations are crucial in crop genetic improvement, with microsatellite markers being commonly used. This study examined the genetic diversity of 23 cashew germplasm accessions and investigated the true hybridity of interspecific hybrids of cashew and its relative. Eight out of 21 CSSRs showed polymorphism in 10 accessions, and dendrogram analysis grouped the accessions irrespective of geographic region. Three CSSR markers were identified for detecting true hybridity in interspecific hybrids, useful for evolutionary studies.