Evaluation of Genotype × Environment Interaction for Forage Yield of Promising Forage Sorghum Lines (Sorghum Bicolor (L.) Moench) using AMMI Model

Due to the spread of droughts and fodder shortages in the country, it is necessary to introduce new cultivars of forage sorghum. Investigating the genotype-environment interaction to select the superior genotype is one of the most important steps of breeding programs. In these programs, evaluating the compatibility of different genotypes to various environmental conditions is important.

Ten promising lines of forage sorghum were studied in a randomized complete block design with three replications at seven regions of Iran (Boroujerd, Zabol, Sanandaj, Shiraz, Karaj, Gorgan, and Yazd) for two years (2018-2019). The AMMI method was used to evaluate the yield stability and compatibility of genotypes.

The results of combined analysis of variance showed that the effects of year, place, year × place, genotype, year × genotype, place × genotype, and year × place × genotype on the fresh and dry forage yield were significant (p≤0.01). The significant interaction of environment × genotype indicates different reactions of genotypes in different environments. The results of AMMI analysis showed that the six main components of the interaction of environment × genotype were significant for fresh and dry forage yields (p≤0.01). For fresh forage yield, the first main component of interaction (IPCA1) had the largest contribution (26.6%) in the expression of genotype-environment interaction and the second to seventh main components were in the next ranks of importance with 18.4, 17, 15.7, 10.5, 7.5 and 4.3%, respectively. For dry forage yield, the first main component of interaction (IPCA1) had the largest contribution (21.8%) in the expression of genotype-environment interaction and the second to seventh main components were in the next ranks of importance with 19.8, 14.7, 14, 11.1, 10.1 and 8.5%, respectively. In total, the cumulative contribution of the seven main components was 98% for fresh forage yield and 97% for dry forage yield. In terms of fresh forage yield, the KFS10, KFS12, and KFS17 lines had the lowest IPCA1 values, which are introduced as stable lines with high general compatibility. In terms of AMMI stability value (ASV) for fresh forage yield, the KFS10 line was determined as the most stable line. In terms of dry forage yield, the KFS2, KFS3, KFS9, and KFS17 lines had the lowest IPCA1 values, which are introduced as stable lines with high general compatibility. The KFS2 line had the lowest amount of ASV in terms of dry forage yield.

Overall, the KFS18 line with high fresh and dry forage yields (121.1 and 32.04 t.ha-1, respectively), low IPCA1, and also optimal forage production in most environments (according to the Biplot model of AMMI) is recognized as a superior genotype.