Extended Abstract

Introduction and Objective:

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 aim of the present study is to identify high-yielding cultivars and genotypes that are stable in terms of grain yield and desirable in terms of other traits using linear mixed effects model (LMM) and multi-trait stability index (MTSI) indices.

Material and Methods: In order to determine the most appropriate planting date and stable genotype in sesame cultivars and genotype using the linear mixed effects model (LMM) and the multi-trait stability index (MTSI), and to evaluate the genotype × planting date interaction on grain yield and determine the stability of grain yield of four sesame genotypes and cultivars using the AMMI and BLUP models, this experiment was conducted during two years (2019-2020) at the Borujerd Agricultural Research Station. 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 year and planting date. Ten plants per plot were used to measure plant height, number of capsules per plant, and 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 a linear mixed effects model (LMM). Variance components were estimated using the restricted maximum likelihood (REML) method. After variance analysis of 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. Multi-trait stability index (MTSI) was also estimated. 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 effect of environment (planting date), genotype and genotype-environment interaction on biomass yield, number of seeds per capsule and oil percentage was significant. Based on biplot analysis, genotype number two, in addition to having the highest grain yield, also had greater yield stability. Based on different values ​​for grain yield and stability index, weighted average absolute best unbiased linear prediction (WAASB) scores, cultivars darab 1 and Ultan were high-yielding and stable, and the superior cultivars in terms of multi-trait selection index (MTSI) were genotype JL16 and Ultan cultivar. The Harmonic Mean and Relative Yield of Genotypic Value (HMRPGV) index identified cultivars Darab1 and Ultan as cultivars that, in addition to grain yield, also had high stability and adaptability.

Conclusion: The results showed that the interaction of genotype by environment (planting date) on seed yield, plant height, biomass yield, number of capsules per plant, number of seeds per capsule, oil percentage and oil yield was significant. Based on the heat map, the ultan cultivar can be considered stable. Based on the multiple trait selection index (MTSI), the JL16 genotype and Ultan cultivar  were also selected as superior genotypes.