Identification of the superior genotypes of pomegranate (Punica granatum L.) using morphological and fruit characters

Abstract Pomegranate (Punica granatum L.) fruits can be used for fresh consumption, industrial processing, and medicinal purposes. Therefore, it is necessary to evaluate the diversity of its different genotypes to be aware of their potential. In the present study, morphological and pomological diversity of 70 native pomegranate genotypes was evaluated to introduce superior selections. Most of the characters showed significant differences among the genotypes. Fruit weight ranged from 103.28 to 407.59 g, and total aril weight per fruit ranged from 51.55 to 238.97 g. Fruit peel color was highly variable and included yellow, yellow‐red, red, and red‐brown. The sunburn and cracking disorders were not observed on the peel of the majority of genotypes. Aril color was highly variable, including light milky, pink, white‐red, red, and red‐black. Seed was soft in 17, semi‐soft in 21, and hard in 32 genotypes. Total aril weight per fruit was positively and significantly correlated with fruit length (r = 0.64), fruit diameter (r = 0.87), fruit weight (r = 0.95), fruit stalk diameter (r = 0.52), fruit peel weight (r = 0.71), and aril shape (r = 0.32). Principal component analysis (PCA) showed that the fruit‐related traits were important for determining differences between genotypes. Based on the ideal values of commercial characters of pomegranate, 15 genotypes were promising and thus could be directly cultivated in the orchards and used in the breeding programs.

TA B L E 1 Descriptive statistics for the morphological traits utilized in the studied pomegranate genotypes  (Holland & Bar-Yakov, 2008), such as "Wonderful" in the United States, "Hicaznar" in Turkey, and "Mollar de Elche" in Spain (Stover & Mercure, 2007).
Genetic diversity in crops, which is essential for food security, the environment, and sustainable development, is being lost.
Due to the attention of many countries and producers, the loss of genetic diversity has become a socio-economic, ethical, and political issue. Therefore, the loss of genetic diversity in crops due to commercialization requires the protection of the existing gene pool not only for the long survival of the species but also for breeding programs. The evolution of powerful new efficient methods for conservation and use of genetic resources has been considered, which in some cases has been beneficial (Esquinas-Alcazar, 2005). The first step in describing genetic resources and introducing them for use in the production chain, and protecting them, is morphological assessments that provide valuable information about their phenotypic diversity (Frankel, 1970). In the present study, morphological and pomological diversity of native pomegranate genotypes at a collection was evaluated to introduce superior selections.

| Plant material
Morphological and pomological diversity of 70 native pomegranate genotypes was evaluated to introduce superior selections at a collection in the Siab area from Koodasht region/Lorestan province/ Iran. The Siab area is located at 33˚30'44"N latitude, 47˚41'32"E longitude, and 1,196 m height above sea level. The genotypes were named based on the Siab area and numbered from Siab-1 to Siab-70.
The genotypes were between 10 and 12 years old and were healthy and in full fruiting stage. The orchard management operations, including nutrition, irrigation, and pest and disease control, were performed regularly and uniformly for the genotypes.

| Morphological and pomological evaluations
Fifty morphological and pomological traits were used to evaluate phenotypic diversity and to select superior genotypes (Table 1).
A total of 20 adult leaves and 20 mature fruits per genotype were randomly selected and harvested. The traits related to dimensions of leaf, fruit, aril, and seed were measured using a digital caliper. A digital scale with an accuracy of 0.01 g was used to measure the weight of fruit, peel, and aril. The qualitative traits (

| Statistical analysis
Analysis of variance (ANOVA) was performed to evaluate the variation among the genotypes based on the traits measured using SAS software (SAS Institute, 1990). Simple correlations between traits were determined using Pearson correlation coefficients (SPSS Inc., Norusis, 1998). Principal component analysis (PCA) was used to investigate the relationship between genotypes and to determine the main traits useful in the genotype segregation with SPSS software.
Hierarchical cluster analysis (HCA) was performed using Ward's method and Euclidean coefficient with PAST software (Hammer et al., 2001). The first and second principal components (PC1/PC2) were used to create a scatter plot with PAST software.

| Morphological and pomological description
Most of the characters measured showed significant differences among the genotypes. These results were confirmed by CV so that 35 out of 50 characters measured exhibited the CVs more than TA B L E 2 Frequency distribution for the measured qualitative morphological characters in the studied pomegranate genotypes  (53) Green (17) --- (16) Moderate (22) High (32) --Fruit calyx form -Close (6) Semi-open (20) Open (44) --Fruit peel color -Yellow (10) Yellow-red (44) Red (10) Red-brown (6) et al., 2006). In the present study, since all the genotypes were examined in the same geographical area, variation in fruit weight was more related to genetics.
Seed was soft in 17, semi-soft in 21, and hard in 32 genotypes.
Soft-seeded pomegranates have a better flavor and taste than others and therefore are more popular in the market. In soft-seeded pomegranates, testa width is thinner, seed and testa densities are lower, and the ratio of testa weight to total seed yield is lower (Prohit, 1985). The heritability of soft seededness in pomegranate is unknown, but it has been found that testa hardness increases in the hybrids obtaining from the crosses between soft-seed genotypes and hard-seed genotypes or soft-seed genotypes (Prohit, 1987).
Fruit taste was predominantly sweet (50 genotypes). The TSS ranged from 14.00 to 23.00%, with an average of 19.06. Therefore, since the TSS value was more than 12%, the juice extracted from the fruits in all genotypes is suitable for commercial uses (Vazquez-Araujo
Estimating the correlation between morphological traits provides useful information for breeders that they can use in designing a high-performance design to study genotypes (Tancred et al., 1995).
This coefficient can also allow the comparison of direct and indirect selections and establish a strategy for the traits that are difficult to select and study (Falconer & Mackay, 1996).

| PCA and HCA
The PCA exhibited 15 PCs, justifying 78.61% of the total variance (Table 3). Six characters, including fruit length, fruit diameter, fruit weight, fruit stalk diameter, fruit peel weight, and total aril weight per fruit, were correlated with PC1 and accounted for 11.77% of the total variance. The PC2 was associated with fruit calyx form, fruit peel color, fruit calyx length, fruit calyx diameter, aril length, aril width, TSS, and fruit taste, accounting for 9.96% of the total variance. The traits, including aril color, fruit juice color, and fruit quality, were correlated with PC3, explaining 7.81% of the total variance.
The scatter plot of the genotypes was created based on effective traits in the PC1 and PC2 (Figure 2). The genotypes varied significantly in the PC1 in terms of fruit length, fruit diameter, fruit weight, fruit stalk diameter, fruit peel weight, and total aril weight per fruit.
In the PC2, the genotypes showed a gradual increase in fruit calyx form, fruit peel color, fruit calyx length, fruit calyx diameter, aril length, aril width, TSS, and fruit taste.
The HCA based on Ward's method divided the genotypes into two major clusters (Figure 3). The first cluster (I) contained 50 F I G U R E 2 Scatter plot for the studied pomegranate genotypes based on PC1/PC2 F I G U R E 3 Ward cluster analysis of the studied pomegranate genotypes based on morphological traits using Euclidean distances I II