Morpho-molecular characterization and genetic diversity analysis across wild apple, (Malus baccata) accessions using simple sequence repeat markers

Abstract Out of five wild Malus species in the world, Malus baccata (L.) Borkh (MB) is reported from the extremely cold areas of north western Himalayas. These are widely used as a rootstock or source of resistance against various biotic and abiotic stresses due to its ecological adaptability and cold hardiness. The study of genetic diversity is an important aspect to be covered for proper utilization of the wild apple germplasm for breeding purpose. The 29 Malus baccata accessions were used to divulge their genetic diversity using morpho-molecular markers. Based on morphological characters, Mahalanobis D2statistics resolved all accessions in four clusters. A set of 85 SSR were used to study molecular diversity among the accessions. The AMOVA stated genetic diversity between populations of genotypes was lower (7%) compared to that observed within and among the individuals of the populations (93%). The effective allele number (2.63) was found to be lower than mean allele number (3.7), with mean heterozygosity as 0.51. The gene diversity varied between 0.10 for Hi02d05 to 0.79 for CH-Vf1.The expected heterozygosity was greater than observed heterozygosity for total analysed loci of SSR. The average PIC value was found as 0.50. The accessions were segregated into two distinct classes using heirarchical clustering method. Further, population structure also differentiated the 29 accessions into two populations, with sub-population I accounts for 18 accessions and sub-population II consisted of only 9 accessions. MB-5 and MB-20 accessions fall in the admixture group. The differentiated populations were validated and reconfirmed by the PCoA analysis. . The morphological features and molecular markers revealed significant level of genetic diversity along with population differentiation among the maintained accessions.