Estimating Combining Ability and Response of Tomato (Solanum Lycopersicum l.) Genotypes to Late Blight (Phytophthora Infestans) Disease

Abstract

Eight tomato varieties were selected based on all over per se performance and late blight disease reaction. Crosses were made in 8×8 half-diallel mating design to produce 28 F1 single cross hybrids. The experiment was conducted in greenhouse at Shambu campus research center in 2020. Necessary data for late blight disease were recorded. In this study highly significant genotypic differences were observed indicating the existence of genetic variability among the crosses to late blight. Analysis of variance for the combining ability indicated GCA and SCA mean squares were significant at (P < 0.001) for all disease parameters. The ratios of GCA/SCA variances for all disease parameters were less than unity implying the predominance of non-additive gene actions. Among all parental lines, ARP tomato d2 and Metadel were identified as stable sources of resistant genes for late blight disease resistance with positive days of first disease appearance and negative disease severity index and AUDPC values for GCA effects. From the analysis of epidemiological data and disease progress curves the Logistic model (R2=96.5) better described the disease progress curves than the Gompertz model (R2=92.5) indicating the presence of delays in epidemics and the infection point of the late blight. ARP tomato d2 and Metadel were identified as a good general combiners for late blight disease parameters. Thus, these parents were recommended to be used in breeding programs with a purpose of developing late blight resistant single cross hybrids. In conclusion of the study, ARP tomato d2 and Bishola parents could be used as a source of resistance gene and potential late blight resistant single cross hybrids (ARP tomato d2 x Metadel, Fetan x ARP tomatod2, Bishola x ARP tomatod2, Metadel x Miya and Bishola x Metadel) were identified. Therefore, it is recommended that these hybrids can be used for direct production where this disease is the most prevalent and/or for further breeding programs in generating hybrids for future use.