Study of genotype-environment interaction effect on sugar yield of sugar beet (Beta vulgaris L.) hybrids

Genotype-environment interaction is one of the most important limiting factors in breeding programs. A comprehensive study of genotype-environment interaction requires powerful statistical methods. Different methods for evaluating the interaction effect of genotype-environment have been proposed by different researchers. Therefore, in the present study, the role of this phenomenon on the sugar yield of sugar beet hybrids and the identification of stable hybrids were studied based on the AMMI, GGE bi-plot, and MTSI stability index methods. For this study, a total of 20 sugar beet genotypes were utilized, comprising 15 recently developed hybrids and five control cultivars (Sina, Dena, Novodora, Modex and Loriquet). Phenotypic assessments of experimental genotypes were conducted in 2021 crop year at four agricultural research stations located in Karaj, Mashhad, Shiraz and Miandoab. These selected sites differed in terms of altitude, latitude and longitude, atmospheric temperature and precipitation, and physical and chemical characteristics of soil. The experiments at each research station were carried out using a randomized complete block design with four replications. Each genotype was planted in a separate plot, consisting of three cultivation rows with a length of eight m and a distance of 50 cm interrow. Throughout the growing season, weed control, irrigation, fertilizer application, and other field management activities were performed based on the recommendations of experts. Additionally, regular monitoring and prevention of pests and diseases specific to sugar beet were conducted at each research station. Stability analysis methods of AMMI, GGE bi-plot, and MTSI stability index were used to analyze the genotype-environment interaction. The results of a combined analysis of variance confirmed the significant effects of environment and genotype on all traits at a one percent probability level. The interaction between them was significant at one and five percent probability levels for all traits except the sugar content and white sugar content. Analysis of the multiplicative effect of the AMMI model showed that the first two components are significant at the one and five percent probability levels, respectively, and together explain 92.20 percent of the interaction variations. The bi-plot of mean yield and the first principal component of the interaction confirmed the superiority of genotype no. 20 due to its high sugar yield and stability. The results obtained from the GGE bi-plot method showed that the first and second components together explain 84.16% of the variations in total sugar yield. According to the GGE bi-plot, Karaj, Shiraz, and Miandoab had a relatively similar reaction in terms of genotype yield rank and in these environments, genotype no. 20 was stable. The reaction of the Mashhad environment was different from the other three environments and in that genotype no. 9 had suitable stability. Based on the results of the MTSI index, four genotypes of 18, 2, 20, and 17 were identified as stable genotypes. In general, the selected genotypes based on the MTSI caused a favorable selection differential in all traits. Among the traits, except root yield, other traits had good selection differential and selection gain. On the other hand, genotype no. 15 had the highest value of MTSI stability index and was unfavorable genotype in terms of studied traits. In general, among breeding hybrids, in the first the hybrid obtained from crossing of (7112 × SB36) × S1– 960132 (genotype no. 2) and then the hybrid obtained from crossing of (7112 × SB36) × S1- 970063 (genotype no. 9) can be used as promising hybrids in final evaluation programs until the introduction of new hybrids. The studied sites were not very closely correlated to be suggested that a site be abandoned to reduce costs for future research; In contrast, most of the tested environments had a high differentiation capability and could make a good distinction among genotypes in terms of sugar yield in genotype-environment interaction studies of sugar beet cultivars.