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This study aims to generate populations with high genetic diversity through hybridization among different wheat genotypes and to evaluate the resulting generations for the selection of superior genotypes suitable for the release of high-potential and well-adapted cultivars in the warm regions of southern and south-west of Iran. From a total of 304 genotypes classified in hybridization blocks at Karaj based on traits such as yield potential, earliness, disease resistance, drought and salinity tolerance, and other agronomic characteristics, parental lines were used. Each genotype panted at two different planting dates with a 15-day interval. Finally 194 successful crosses were done in this project. Harvested seeds from each crossing program separately will be sown next to parental line/cultivar in the following year as F1 nurseries and will be evaluated for the removal of possible selfed plants. It also aims to make additional complementary crosses as Top-Cross. Moreover, 104 F1 entries from simple and complex crosses were sown and evaluated to generate F2 populations for 2024-2025 cropping cycle.
The F2, F3, F4, and F5 generations included 90, 491, 72, and 90 bulks, respectively, while the F6 generation consisted of 35 pure lines. After harvest, spikes were threshed, and seeds were screened, resulting in the selection of 613 single plants from the F2 population. Furthermore, 96 entries from the F3 generation, 47 entries from the F4 generation, 58 selected single plants from the F5 generation, and 35 pure lines from the F6 generation were advanced to subsequent breeding cycles. Simultaneously, a Preliminary Wheat Screening Nursery (PWSN) was conducted in the same year with 80 pure lines derived from the F6 generation of the previous season (2022–23), evaluated in an augmented design alongside local checks (Sareng, Mehregan, and Barat) at both Darab and Dezful stations. Based on performance and desirable traits, 21 superior pure lines with higher yield compared to the checks were selected and introduced to the National Warm Region Yield Trials.
The breeding method employed is a modified pedigree-bulk approach. Accordingly, in the F2 generation, single-plant (pedigree) selection will be carried out, while in the F3 and F4 generations, selection will follow a modified bulk method. In the F5 generation, pedigree selection will again be applied, with individual plants numbered separately. The selected F5 plants from the previous year will be grown as three-meter rows in the F6 generation, where selection among pure lines will be conducted. The selection criteria include plant type (uniform spike height, absence of spike and tiller stratification, and narrow tiller angle), desirable agronomic type, spike architecture (dense spikelets, closed glumes and lemma, and presence of spreading awns), earliness, resistance to yellow and brown rusts and Septoria leaf blotch, as well as grain shape (non-shriveled kernels). In Dezful, the F3 generation will undergo artificial inoculation with a single isolate of Septoria tritici to screen and select resistant entries. In the F6 generation, superior lines, provided they are pure, will be harvested, and seeds will be produced for preliminary yield trials at both Dezful and Darab stations.
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