Genetic diversity of Dalat tomato varieties revealed by morphological traits and simple sequence repeat markers

Abstract

By estimate the number of genetic distance among accessions, genetic diversity plays an important role in the adjustment of the mating or breeding of individuals or organisms where genes are closely related in the hybrid process. This study was conducted to determine genetic diversity among 15 Dalat tomato varieties (Lycopersicon esculentum Mill.) using 9 simple sequence repeat (SSR) markers and 36 morphological descriptors. The analysis of morphological markers showed a low variation. While the cultivars were classified in three fruit shape classes, fruits having flattened and slightly flattened shape occupied 53.33% of the collection. In contrast with limited morphological variability, the medium values of SSR polymorphism confirmed the average level of genetic variability among these cultivars. PCR-amplification between genomic DNA of 15 accessions and 9 SSR primer pairs yielded 8 alleles in 4 different polymorphic loci within the tomato’s genome. Allele frequency ranged from 0.07 to 0.93 and observed heterozygosity (Ho) varied from 0.00 to 1.00 with an average of 0.48, thereby revealing a low degree of homozygosity in these landraces. All the identified SSR markers were found in a range from 0.12 to 0.5 in terms of Polymorphic Information Content (PIC), with a mean value of 0.34. Overall, based on the statistical number of genetic distance in UPGMA dendrogram, 15 accessions were grouped into 2 main groups and 4 sub-groups. Given a higher polymorphic level of SSR markers, SSR markers were more capable of distinguishing landraces into distinct genotypes expressing fruit and yield characteristics than morphological markers. Despite of the short genetic distance, the phenotypic and genetic variation allowed the classification of a collection of Dalat tomato varieties. This finding could be the scientifically fundamental initiative for identification the genetic distance to support the effective utilization of initial materials in breeding programmes to improve crop heterosis and produce hybrids of desirable characteristics in Vietnam. KEYWORDS: tomato, Lycopersicon esculentum Mill., genetic diversity, genetic distance, SSR markers, morphological markers