Investigation of Morphological and Important Crop Characteristics Variation among Watermelon (Citrullus lanatus) Ecotypes using Multivariate Statistical Analysis

Watermelon (Citrullus lanatus) is a tropical or semi-tropical plant and it is rich in antioxidant compounds. The most production area of watermelon belongs to China followed by Turkey, United States, Iran and Republic of Korea. The study of genetic diversity is important not only for the conservation of plant materials, but also for using the heterosis in breeding programs to produce the uniform with high yielding hybrids. The province of Kerman is one of the most important areas of watermelon cultivation and production in Iran. In present study, we used the Multivariate Statistical Analysis based on several morphological and economically important physiological characteristics to evalute the variaton of the thirty ecotypes of watermelon that were collected from different parts of the Kerman province but not all around of Iran.
Material and The collected ecotypes were cultivated in a completely randomized block design with three replications in Kerman. Sixteen morphological and physiological traits were evaluated. Analysis of variance, estimation of the descriptive statistical parameters, cluster analysis, the discriminant and the Principal Component Analysis (PCA), the correlation between traits and the cophenetic correlation coefficient were calculated using statistically softwares. Components of variance and coefficients of genotypic, phenotypic and environmental variation, also broad sense heritability were calculated with the corresponding formulas.
Analysis of variance of the evaluated traits, showed significant differences . Correlation between fruit weight and most of the traits was positive. The length, width and diameter of seeds that directly affect the seed yielding showed a positive correlation with this trait. So it is useful for increasing seed yielding. Also, the fruit length, width and diameter as well as flesh weight which are important in increasing of fruit weight, showed a positive correlation with this trait and can lead the selection for fruit yield. Cluster analysis using Ward method was classified the studied ecotypes into four groups. Based on the Principal component’s analysis, the first and second components showed more than 92 of the percent of the total variation. The coefficient of genetic diversity and heritability of the most of the studied traits were high, that indicates the high selection efficiency for these traits. The results of this study showed a great deal of diversity morphological traits in studied ecotypes. The accessions had been divided into four groups in which group 1 had the highest seed yield. Therefore, accessions of this group must be used to enhance yield. The Hejrag accession showed the minimum length, width and diameter of seeds, as well as the seed weight, so it could be used in the production of small-size seed cultivars in breeding programs.
This study supports that quantitative traits are useful tool for preliminary evaluation of genetic diversity in watermelon ecotypes. Based on Correlation studies, the traits namely, Seed diameter, Number of male flowers, Number of leaves per plant, Number of nodes, Fruit Length, Fruit Diameter and Fruit Weight had positive association with Flesh weight. Selection of parents must be based on the wider inter cluster distance and superior mean performance for fruit yielding and quality in four distinct groups. The ecotype, namely, Yazd was found to be superior for pH, flesh weight and Thickness of pericarp, so it should be utilized in further breeding program for developing superior varieties. Also, the Neyshabor accession showed the maximum seed length, width, diameter and 100 seed weight, so it could be used for production of large size seed cultivars.
Acknowledgements: This work was supported by Iranian national science foundation (Project No. 92033924).