Introduction: Identifying and selecting suitable lines and varieties for wheat cultivation in each geographical area is of great importance. New wheat lines are commonly evaluated through advanced experiments in similarly climatic regions, using the results to identify appropriate varieties for cultivation in each area within most breeding programs worldwide. The aim of this research is to conduct an initial assessment of wheat lines and identify superior lines for further testing, with the goal of introducing new varieties in the southern region of Fars province.
Materials and Methods: This research was conducted to evaluate and select superior bread wheat lines with desirable agronomic traits at the Agricultural Research Station of Darab during the agricultural years 2019-2020 and 2020-2021. The lines used in this research were selected from various experiments conducted in Zabol, Darab, and Karaj, as well as from international trials. Additionally, double haploid lines derived from a joint program between the Seed and Plant Improvement Institute and Florimond Desprez in France were included.. In the first year, 315 pure bread wheat lines were examined, and 65 superior lines were selected using the Selection index of ideal genotype (SIIG). In the second year, these lines, along with three control cultivars, were planted and evaluated in an alpha lattice design.
Results and Discussion: The analysis of variance for quantitative traits in the control varieties indicated no significant differences between the blocks. Performance analysis of the traits shows that the two traits of grain yield (equivalent to 16.45) and grain filling rate (equivalent to 14.78) had the highest coefficients of variation, thus exhibiting the greatest diversity among the quantitative traits. Additionally, the minimum and maximum grain yield of the evaluated lines were 1.83 and 8.33 tons per hectare, respectively. The results of the coefficient of variation parameters, along with the minimum and maximum values, confirm the presence of high diversity in grain yield. Consequently, using the selection index SIIG, lines were selected with an average yield of 7.49 tons per hectare, which was higher than the average yield of the control genotypes (6.97 tons per hectare) and the total lines (6.50 tons per hectare). In the second year, significant differences were observed between the lines for most examined traits. The results of this study also indicate that the average performance of 65 selected lines in the second year was 5.04 tons per hectare, which represents a decrease of approximately 2 tons per hectare compared to the performance of the same lines in the first year. The rainfall recorded in the first year was 486.2 mm, while in the second year, it was 73.7 mm. An analysis of the average temperatures during the two critical months of grain filling, namely April and May, shows that the weather in the first year during these months was cooler than in the second year. This contributed to the reduction of the thousand-grain weight from 42.19 gr in the first year to 33.50 gr in the second year. Regarding selection differential, the highest and lowest values corresponded to the traits thousand grain weight (4.80%) and height (-0.89%), respectively. Additionally, the total selection differential, both positive and negative, was obtained as 5.60% and -2.69%, respectively. The SIIG categorized the lines into six groups. Genotypes number 28, 36, 60, 25, 45, 53, 35, 12, 33, 11, 37, 16, 34, 19, 59, 48, 49, 8, and 30 were identified as the best genotypes with yields exceeding that of the control cultivars. Examination of the pedigree of the top selected lines showed that several of the top selected lines included parents PASTOR, BORL14, KACHU, and WBLL1. These parents likely played a crucial role in the success of these lines compared to other tested lines. The selected parents in this research possess beneficial genes (such as drought resistance genes from the top selected lines originating from SAWYT, temperature tolerance from HTWYT, rust resistance from 13STEMRRSN, etc.) that have enhanced yield and quality of wheat under specific climatic conditions.
Conclusion: The results demonstrated the effectiveness of the SIIG in classifying the genotypes, and based on the findings, the selected lines were introduced for adaptability testing in national uniform trials in the hot climate of the country.