Assessment of Genetic Variability and Character Association of Watermelon (<i>Citrullus lanatus</i>) varieties Using Agromorphological Characters

Understanding genetic diversity and germplasm classification through agro-morphological characterization is fundamental in order to provide information for genetic resources conservation and breeding programs. The overall objective of this study was to assess the genetic variability of watermelon varieties cultivated in Cameroon. Five watermelon (<i>Citrullus lanatus</i>) genotypes were evaluated for genetic variability, heritability, and genetic advance for yield and its contributing characters in watermelon during 2017. Analysis of variance showed significant variation for all the studied characters, indicating the presence of sufficient variability in the material. Germination rates of the five varieties vary from 61.11 ± 5.82 to 90.71 ± 1.12% for Sugar Baby and Kaolack. Emergence time ranges from 7.03 ± 0.87 (Kaolack) to 8.73 ± 1.03 (Koloss), while flowering time varies from 28.27 ± 0.45 (Crimson Sweet) to 36.24 ± 0.32 (Sugar Baby) days. The number of fruits (fruit count) show that Kaolack has the highest number of fruits per plant (3.55 ± 0.89), followed by Crimson Sweet (3.32 ± 0.5) while Koloss presents the lowest number of fruits per plant (2.12 ± 0.27). Of the 45 correlations performed, 26 were negative and 19 were positive. All negative correlations were not significant at the 5% level, while 5 positive correlations were significant. This result shows that length of fruit is correlated with weight of fruit (0.99) and weight of one hundred seeds (0.88). Moreover, the correlation between these two fruit characteristics (weight of fruit and length of fruit) appeared strong and positive (0.92). The phenotypic coefficient of variation ranged from 20.35 to 201.49 for the seed shape and weight of fruit parameters, respectively, while the genotypic coefficient of variation ranged from 17.72 to 198.65 for the same traits, respectively. All the traits studied showed that the phenotypic variance was higher than the genotypic variance. High broad-sense heritability coupled with moderate-high genetic advance was recorded for weight of one hundred seeds (11.63), while high broad-sense heritability associated with low genetic advance values was obtained for seed shape (0.21), seedling emergence time (5.89), and number of fruits per plant (6.43). Only the first two axes of the principal component analysis were taken into account because they explained about 92.31% of the variation observed in the varieties. The main parameters associated with these two axes were weight of fruit, length of fruit, flowering time, weight of one hundred seeds and life cycle. Based on the variation, 5 genotypes were grouped into three classes using the K-means classification. Further studies involving biochemical and molecular markers are recommended for deeper characterization.