Evaluation and selection in wheat segregation populations and preliminary yield trial

Segregation of traits in hybrids of bread wheat begins from F2 population and continues until several generations later. At first, the best combinations of hybrids were selected and then from among of them base of traits: plant height, strong tillers, spike form, resistance to shattering, preharvest sprouting and reaction to diseases such as yellow rust, leaf rust, powdery mildew, septoria leaf blotch and scab were selected individual plant. In this study, in F2 generation 352 population, F3 generation 491 numbers, f4 generation 334, F5 generation 55, F6 generation 33 and F7 generation 117 of bread wheat evaluated in modified pedigree-bulk method. At first, from among of F2 generation were selected 2320 individual plant base of morphological traits in the field, then thrashing and discarding the shriveled seeds. The seeds remain from each number bulked together that they were 271 numbers for F3 generation. In F3, F4 and F5 generations some numbers of the best spikes from each one selected in bulk method in the field. Numbers of plants F3, F4 and F5 generations were 2571, 1539 and 374 respectively. After thrashing and discarding the Shriveled seeds, were selected 359 numbers for F4, 247 numbers for F5 and 219 numbers for F6 generations.In F6 generation, some numbers of the best spikes were selected in the filed based of pedigree method. In the field from each selected number 10-20 spikes was selected and individually harvested and thrashed. Then 429 numbers were selected after discarding the shriveled seeds for F7 generation. In F7 generation after checking all of plants, 32 numbers of them that were the best for all traits were selected. After thrashing and checking finally all of 32 pure lines were selected for studying in preliminary test. In this study 78 bread wheat lines from Gorgan crosses in 1382-1383 year were planted with Tajan and N-79-12 after every 5 lines as a check. The planting of each line did base on 1000 kernel weight and 350 seed density per one-meter square. Area of each plot was 7.2 m2. Morphological and agronomy traits and reaction of lines to leaf diseases were measured. Selection of lines did based on seed yield and morphological traits and reactions to diseases. Finally, 27numbers of the best lines were selected to evaluate in the PRWYT experiment in 1383-1384 year. Key words: bread wheat, selection in the segregation generations, preliminary test.