ارزیابی عملکرد و تجزیه و تحلیل شجره لاین های انتخاب شده گندم نان تحت شرایط تنش خشکی آخر فصل

در این تحقیق تعداد 291 لاین گندم نان با هدف انتخاب لاین‌های متحمل تنش خشکی آخر فصل به روش مشاهده‌ای بدون تکرار در دو شرایط نرمال و تنش مورد مطالعه قرار گرفتند. از صفات درصد سبز، تعداد روز تا سنبله دهی، رسیدگی فیزیولوژیک، ارتفاع بوته، رنگ دانه، وزن هزار دانه، درصد خوابیدگی، ریزش دانه، و عملکرد دانه یادداشت برداری شد. شاخص‌های sti ، tol ، gmp ، mp و ssi برای صفات وزن هزاردانه و عملکرد دانه در کلیه ژنوتیپ‌ها محاسبه شدند و در نهایت تعداد 34 لاین برتر و متحمل تنش خشکی آخر فصل با توجه به شاخص‌های sti و ssi در دو مرحله مورد گزینش قرار گرفتند. تجزیه و تحلیل شجره‌نامه لاین‌های انتخابی نشان داد که ژنوتیپ‌های pastor ،wbll1 ،skauz و y50e به ترتیب با 11/21 ، 6/34، 4/04 و 4/04 درصد بیشترین سهم و ژنوتیپ‌های chibia ،kachu و 1 73 240 به ترتیب با 0/01، 0/02 و 0/02 درصد کمترین سهم را در ریخته ارثی لاین‌های متحمل تنش خشکی آخر فصل داشتند. همچنین سهم برخی از ارقام گندم مانند امید، پیشتاز، پارسی، مرودشت، البرز و اترک در ریخته ژنتیکی لاین‌های انتخاب شده به ترتیب 2/78، 2/39، 1/47، 1/47، 1/44و 0/09 درصد بود. با توجه به نتایج پیشنهاد می‌شود که علاوه بر ارقام گندم فوق می‌توان از ارقامی که دارای ریخته ارثی ژنوتیپ‌های pastor ، kauz ، skauz ، wbll1 ، pbw343 ، y50e و munal #1 ‌باشند نیز در برنامه تولید ژرم پلاسم با صفات زراعی مناسب و متحمل تنش خشکی آخر فصل در اقلیم معتدل کشور استفاده کرد.

evaluation of yield and pedigree analysis of selected wheat lines under late season drought conditions

introductiondrought stress is one of the most important and common environmental stresses that restricts agricultural production and reduces production efficiency in semi arid and dryland areas (sarmadnia, 1993). information on yield stability of genotypes under both favorable and drought stress conditions is essential to identify drought tolerant genotypes by plant breeders and genotypes with good performance in both environments are preferred (uddin et al., 1992). in international maize and wheat improvement center (cimmit), the f3 and f4 generations are selected under limited irrigation conditions. the selected plant materials in the fifth and sixth generations are evaluated under normal conditions, and in seventh and eighth generations performance comparison and other evaluations are studied under water stress and natural conditions. this method of evaluation and selection under stress and non stress conditions has been suggested and applied by many researchers on wheat and other crops (ehdaie et al., 1988). the goal of this study was selection of drought tolerant bread wheat lines based on their tolerance indices and pedigree analysis.materials and methodsin this experiment, 291 lines and cultivars of bread wheat along with four check cultivars including parsi, pishtaz, sirvan, and sivand were evaluated to identify tolerant genotypes for terminal drought using two identical experiments, one under non stress condition and the other one under drought stress condition (irrigation cut off after 50% of anthesis). experiments were conducted using the observational method without replication. during the developmental stages, the traits including green percentage, days to heading, days to maturity, plant height, grain color, thousand grain weight, lodging percentage, shattering and grain yield per plot were recorded. drought susceptibility and tolerance indices such as sti, ssi, gmp, mp and tol were calculated for all the investigated entries based on 1000 grain weight and grain yield. in order to investigate the genetic background of selected lines, the percentage of genetic contributions of each genotype was calculated based on the pedigree of the lines.results discussionthe results indicated that under both stress and non stress conditions, the selected lines were relatively early mature. comparison of arithmetic means (mp), geometric mean (gmp) and drought tolerance index (sti) of the genotypes revealed that selection based on these criteria leads to the selection of high yield genotypes under both stress and non stress conditions. in terms of grain yield, genotypes 33, 2, 34, 23, 10 and 11 had the lowest ssi, which was associated with a higher yield of these lines under drought stress. also, in terms of 1000 grain weight, genotypes 10, 11, 32, 33, 34, 8 and 5 had the lowest ssi indices where this trait was significantly correlated with high seed weight under drought stress. lines 11, 14 and 34 had the highest sti index for grain yield and 1000 grain weight, which was significantly associated with high grain yield and 1000 grain weight under normal conditions. finally, 34 superior drought tolerant lines were selected in two stages according to sti and ssi indices. pedigree analysis of the selected lines showed that genotypes pastor, wbll1, skauz, and y50e had contributions of 11.21%, 6.34%, 4.04%, and 4.04% in germplasm composition under drought condition, respectively, indicating their impact on drought tolerance. on the other hand, genotypes chiba, kachu and 1 73 240 had 0.01%, 0.02%, and 0.02% contribution in germplasm composition under drought conditions, respectively, showing no influence in drought tolerance. conclusionthe results of this study showed that the genetic structure of some iranian wheat cultivars such as omid, pishtaz, parsi, marvdasht, alborz and atrak, respectively, made contributions of 2.78%, 2.39%, 1.47%, 1.47% and 1.44% to the genome of the selected lines. finally, it was suggested that, in addition to the above mentioned iranian cultivars, breeding lines derived from genotypes such as pastor, kauz, skauz, wbll1, pbw343, y50e and munal #1 can be used in breeding programs to produce suitable germplasm with early maturity and tolerance to terminal drought stress for temperate climate of iran.