Genetic diversity detection of seed-propagated walnut (Juglans regia L.) germplasm from Eastern Anatolia using SSR markers

Abstract

Continuous seed propagation in Turkey has given rise to a great number of seedling walnut trees which represents valuable walnut genetic resources. The number of native walnut trees is estimated to be over 5 million in Turkey and they possess large phenotypic variability in yield, nut and kernel characteristics, late bud breaking, late flowering, winter hardiness and tolerance to diseases. Progress in walnut breeding requires the exploitation of genetic variation among cultivars and landraces. In this study, we used 32 local diverse walnut genotypes obtained from seeds and 2 standard cultivars (‘Sebin’ and ‘Bilecik’). This study implemented 21 previously used simple sequence repeats (SSR) markers to determine genetic diversity. The analysis revealed 135 alleles with an average of 6.43 alleles per locus. Genetic similarity ranged from 0.23 (for samples KW22 and KW29) to 0.87 (for samples KW27 and KW28). The highest number of alleles per locus was obtained from WGA276 locus (11 alleles), followed by WGA054 (9 alleles), WGA202 and WGA321 (8 alleles) while the lowest number was detected in WGA027. According to the morphological and molecular data, the genotypes differed from each other and the cvs. Sebin and Bilecik. The majority of the genotypes had higher fruit weight and some of the genotypes had higher kernel ratio than cvs. Sebin and Bilecik implying the importance of registering genotypes as cultivars. This research provides information on the genetic relationship of walnut genotypes and cultivars and emphasises the importance of protection and utilisation of seed-propagated walnut genetic resources.