Association mapping for pomological traits in grape (Vitis vinifera L.) using ISSR markers

Grape (Vitis vinifera L.) is an important fruit crop and widely cultivated in the glob because of the nutritional, medicinal and economical values. Since the economic value of cultivar depends on different characteristics, thus detailed knowledge on genetic behavior and identification of genomic loci linked to these traits will help to improve plant cultivars. In this investigation, relation and linkage between of ISSR markers with some of pomologic traits such as yield and quality-related traits in West Azarbaijan grape cultivars was evaluated through MLM association models in Structure and TASSEL software. 45 grape cultivars from West Azarbaijan agricultural and natural resources research germplasm bank were investigated. Berry quality traits were evaluated over three consecutive years onto 10 replications per cultivar. Genomic DNA was extracted following the Doyle and Doyle method (1987) and Polymerase chain reaction (PCR) was performed with 17 ISSR primers. Scoring of amplified fragments was performed according to present (1) or absence (0) of each band marker, and the produced binary data were served for statistical analysis. The Bayesian approach in the software package Structure was used for estimating the population structure. Identification of genomic loci linked to these traits were done with mixed linear model (MLM) in TASSEL software. Based on the 17 ISSR markers used in this study, population genetic structure subdivided into two subpopulations (K=2). Based on results in Barplot 20 cultivars (44/44%) of the studied cultivars were assigned to P1 group and 17 cultivars (37/78%) assigned to P2 group and the remaining ones (17/78%) were categorized into the mixed group. In this investigation, of 2775 ISSR markers pairs, 0.72% showed a significant level of LD (P ≤ 0.01). results showed the significant association (P ≤ 0.01) of 12 ISSR markers with genomic region controlling the studied traits. 1 locus (UBC825-4) was identified for TSS, 1 locus (UBC890-2) was identified for pH, 2 loci (UBC817-2 and UBC825-5) were identified for seed weight, 2 loci (UBC836-7 and UBC855-2) were identified for seed number, 3 loci (UBC812-3, UBC817-4 and UBC864-2) were identified for cluster width, 2 loci (UBC817-4 and UBC864-2) were identified for cluster weight and 1 locus (UBC826-4) was identified for fruit set in controlled pollination. Our results suggest the importance the power and precision of MLM association mapping in grapevine. Some loci were common for more than one trait. The common markers are useful in plant improvements program because they augment efficiency of marker selection through concurrent selection for several characters.These ISSR loci identified in this study associated to quality traits may be applied in marker-assisted breeding programs for improving some important traits in grape.