Genetic Analysis of Resistance Against Race 1.2 of Vascular Wilt Disease in Iranian Melon (Cucumis melo L.) Landraces

To understand the genetic control of resistance against yellowing variant of fusarium wilt of melon (FOM 1.2y) in Iranian melon landraces, seven commercial landraces were studied in a half diallel model ( including F1s and parents) using Gardner- Eberhart Analysis II. Parents included: Magasi, Jalali, Sooski, Khaghani, Chapalizi, Semsori and Shadegani. Eighteen seedling of each genotype (totally 36 plants in the experiment) were evaluated using randomized complet block design with three replications. Indices including: area under disease progress curve (AUDCP), disease severity index (DSI) and latent period (LP) were calculated to evaluate the reaction of genotypes. Magasi had the lowest positive difference with resistant check in AUDPC and DSI, and had the lowest negative difference with the resistant check, therefore, identified as the highly resistant parent in this experiment. All genetic variances and their components including additive and dominance (non- additive) were estimated as significant at least at P < 0.05 followed by corresponding significant additive and dominant coefficients of variation. The highest GCA/SCA ratio (0.86) was calculated for DSI which showed the highest significant broad sense and narrow sense heritability ( 0.82 and 0.71, respectively). The results showed the higher importance of additive variance comparing with non-additive (dominance) variance for DSI. Magasi and Chapalizi were identified as the best resistance parents according to estimated GCA. Considering significant broad sense and narrow sense heritability for LP (h2b=0.66, h2n=0.47) followed by significant additive and non-additive variances, it is concluded that LP can be used as a reliable index in breeding programs for improving resistance against FOM 1.2y.