Journal of Crop Breeding

Extended Abstract
Background: The identification of high- yield cultivars and genotypes with adaptation to a wide range of environments (planting date) is one of the major goals in crop breeding programs. Combining the best linear unbiased predictions (BLUP) and additive main effects and multiplicative interaction (AMMI) methods in multi-environment experiments and multi-trait stability selection (MTSI) helps to better evaluate cultivars and plant genotypes and achieve more accurate results. The present study aims to identify high-yielding cultivars and genotypes that are stable in terms of grain yield and desirable in terms of other traits using the linear mixed effects model (LMM) and multi-trait stability index (MTSI) indices.
Methods: To determine the most appropriate planting date and stable genotype in sesame cultivars and genotypes using the LMM and MTSI, evaluate the genotype × planting date interaction on grain yield, and determine the grain yield stability of four sesame genotypes and cultivars using the AMMI and BLUP models, this experiment was conducted at the Borujerd Agricultural Research Station during two years (2019-2020). This experiment was conducted as a two-factorial in a randomized complete block design with three replications. The experimental factors included four planting dates (June 13, July 11, July 30, and August 15), and four genotypes (Darab1, Oltan, Halil, and JL16). Each environment was a combination of the year and planting date. Ten plants per plot were used to measure plant height, the number of capsules per plant, and the number of seeds per capsule, which were selected from each plot after physiological maturity. The mean of the ten plant data was used in the analysis of variance of the data. For statistical analyses, the multi-environmental experiments analysis package, called Metan Ver.1.9.0, was used in the R software environment. The uniformity of experimental errors across environments was tested using the Bartlett method, and then the combined analysis of variance of the data was performed using the restricted maximum likelihood (REML) method, assuming a fixed genotype effect and a random year and location effect. The significance of random effects was tested by the likelihood ratio test (LRT) and fixed effects by the least squares method. To estimate stability quantities, singular value decomposition (SVD) was applied to the matrix of best linear unbiased predictions (BLUPs) obtained from genotype-by-environment interactions with an LMM. Variance components were estimated using the REML method. After analysis of variance for the data, the characteristic roots obtained from the AMMI analysis on BLUP were used to estimate the stability parameters WAASB and WAASBY (for simultaneous selection based on average yield and stability), and the best genotypes were selected with these two indices. The MTSI was estimated as well. Genotypic stability values were obtained from the harmonic mean index of genotypic values (HMGV). Genotypic compatibility was assessed based on the relative yield index of genotypic values (RPGV), and the harmonic mean index and relative yield of genotypic values (HMRPGV) were used to simultaneously assess stability, compatibility, and grain yield.
Results: The effects of the environment (planting date), genotype, and genotype-environment interaction were significant on biomass yield, the number of seeds per capsule, and oil percentage. Based on the biplot analysis, genotype 2, in addition to having the highest grain yield, gsined greater yield stability. Based on different values for the grain yield and stability index, WAASB scores, cultivars darab 1 and Ultan were high-yielding and stable, and the superior cultivars in terms of the MTSI were genotype JL16 and the Ultan cultivar. The HMRPGV index identified Darab1 and Ultan as cultivars that, in addition to grain yield, showed high stability and adaptability.
Conclusion: The results showed that the genotype by environment (planting date) interaction was significant on seed yield, plant height, biomass yield, the number of capsules per plant, the number of seeds per capsule, oil percentage, and oil yield. Based on the heat map, the Ultan cultivar can be considered stable. Based on the MTSI, the JL16 genotype and Ultan cultivar were selected as superior genotypes.