عنوان مقاله [English]
Introduction: Pomegranate (Punica granatum L., Punicaceae family), a native Iranian horticultural plant, is used as fresh fruit and also for other products and has special economic position in the world. It is estimated that pomegranate fruit production in Iran was about 900000 tons in 2016 which provinces of Fars, Markazi, Khorasan, Yazd and Isfahan had the highest production respectively. Iran is the center of diversity and most probably center of origin of Pomegranate, so during the years, many attempts have been done to collect different genotypes. The National Research Station of Pomegranate of Saveh has three set collections including 760 genotypes collected from all around of Iran. Assessment of genetic variation among these genotypes to use in breeding programs should be considered as first priority. Researchers use different methods to measure genetic diversity of plants including DNA markers, isozymes and morphological traits. Using morphological characteristics that are easily measured and have high heritability is a convenient tool to assess the amount of genetic diversity of plants.
Material and Methods: In order to determine genetic variation and heritability on morpho-pomological traits, pomegranate genotypes were selected from different habitats of Iran that are already planted in the collection of National Research Station of Pomegranate of Saveh in 2016. Genotypes that had similar descriptor or genotypes that had not sufficient fruit to get involved in the experiment, were excluded. Selected genotypes (156 genotypes) were evaluated based on a completely randomized design with three replications using nine morphological traits including length of calyx, width of calyx, number of seed in 100-gram aril, thickness of peel, weight of fruit, length of fruit, width of fruit, weight of peel, weight of aril. Biochemical characteristics of fruit including total soluble solids, titrable acidity, maturity index, pH, EC, anthocyanincontain and absorbable color of juice were measured for each genotype without replication (five fruit were selected randomly for each genotype). Statistical analyses including analysis of variance, correlation coefficient, and broad sense heritability, phenotypic and genotypic coefficient of variation were estimated using SAS 9.0 software.
Results and Discussion: Analysis of variance showed that the effect of genotypes in each trait is highly significant (p-value=0.01), indicating a wide variation among these genotypes. Considering range for each trait reveals remarkable differences between genotypes especially for number of seed in 100-gram aril and anthocyanin content. Results showed that among 9 morphological traits, aril seed (g 100 aril-1) and peel thickness, also among 7 chemical traits, anthocyanin content, absorbable color of juice and maturity index had the highest variation. The most positive and significant correlation coefficients was observed between fruits weight with length and diameter of fruit, length and diameter of calyx, aril weight, seed number (g 100 aril-1) and peel thickness. Correlation between qualitative and quantitative traits were not significant. The highest phenotypic and genotypic coefficient of variation was observed on fruit weight, peel thickness, seed number (g 100 aril-1) and aril weight. A high broad sense heritability was observed for aril weight (g 100 aril-1), fruit weight and peel thickness.
Conclusion: Based on the results of this study, there was a high genetic variation among genotypes for most traits. As it was expected, Iranian collection of pomegranate is a rich source for this plant and highly supporter for other breeding researches. High correlation coefficient of fruit weight with other morphological traits is useful for early selection of high performance genotypes. For instant, genotypes with high diameter of calyx most probably will produce high yield. There was not statistically significant correlation between morphological and biochemical characteristics. That is to say genotypes with low yield should not be excluded in further research programs because of their beneficial biochemical traits; they can be involved in crosses with high yield genotypes to improve their biochemical characteristics. Pomnograte genotypes with good quality traits are also useful for industrial, pharmaceutical and nutraceutical purposes. Results of our experiment indicate that due high broad sense heritability of aril weight, fruit weight, peel thickness and aril weight, environmental effect on these traits is less than genetic effect. Therefore, selection based on these traits could successfully be used to improve genetic base of pomegranate genotypes in the next generations. Also based on the results of this research Hasteriz- Shahdad and Domaze- Izeh genotypes were the best for soft seed, color and flavor fruit.