Evaluation of genetic diversity in some loquat genotypes based on pomological characteristics in Golestan province

Loquats have formed different ecological types during their cultivation and adaptation in different parts of the world. The first step in the breeding operation is the identifying of the spread center accompanied the studying of the variation between genotypes. In this research, 20 loquat genotypes were evaluated using fruit morphological markers to identify and select the superior genotypes in Golestan province.
The fruits of the genotypes were harvested in the ripening stage and 25 fruit quantitative and qualitative characteristics were assessed in the laboratory. The maximum, minimum, mean values, diversity coefficient index, correlation between traits and the cluster and principal component analysis were performed.
The results showed that there were some significant differences among genotypes based on physicochemical characteristics. Among the genotypes, fruit weight and length varied from 12.87 to 23.80 g and 25.67 to 33.70 mm, respectively. Fruit was roughly round in majority of genotypes. Fruits contained 1.14 - 4.33 seeds depending on the genotypes. Fruit flesh ranged from 2.5 to 5.92 times of seeds weight in genotypes 1 and 20, respectively. The highest (87.96%) and lowest (77.60%) amount of flesh humidity were recorded in genotypes 2 and 20, respectively. The percentage of seed dry matter differed from 41.12 to 51.27%. The highest total soluble solids (17.73%) were observed in genotype 13, whereas genotype 3 had the highest titratable acidity (1.16%) and vitamin C (38.10 mg/100g fresh weight). In addition, to determine the main discriminator traits among the genotypes, the principal components analysis of 19 quantitative traits was conducted and the evaluated traits were categorized within 5 factors, accounted for 89.95% of total variance. The first factor was related to fruit physical characteristics while the second factor was related to seed characteristics. These two factors accounted for 55.5% of total variance. Factor analysis showed that characteristics such as: fruit length, diameter, weight and volume, seed length, fresh and dry weight, seed dry matter percent, seed length to diameter ratio and seed number had the highest effects on genotypes diversity. Cluster analysis of 19 quantitative traits divided the genotypes into five main groups. Fresh flesh weight showed positive correlation with fruit length and diameter, weight and volume at
Finally, genotypes with superior fruit characteristics such as: higher fruit weight, lower seeds within fruit or including higher qualitative traits may be introduced as promising ones for future evaluation, breeding or propagation programs and commercial orchards establishment.