تجزیه ژنتیکی صفات فیزیولوژیک گندم نان تحت شرایط نرمال و تنش کمبود آب آخر فصل

بررسی پاسخ‌های فیزیولوژیکی در گندم نان نقش بسزایی در شناسایی مکانیسم‌های موثر در افزایش تولید محصول تحت شرایط نامساعد محیطی به‌ویژه تنش کمبود آب دارد. در این مطالعه نحوه توارث صفات فیزیولوژیک و عملکرد دانه در دو جمعیت گندم پارسی ×بک‌کراس زمستانه روشن و سیستان ×بک‌کراس زمستانه روشن تحت شرایط نرمال آبی و تنش کمبود آب آخر فصل با استفاده از طرح ژنتیکی تجزیه میانگین نسل‌ها مورد بررسی قرار گرفتند. نتایج حاصل از مقایسه‌های میانگین نشان داد که در هر دو تلاقی میزان عملکرد دانه در شرایط تنش کمبود آب دچار کاهش شد. به‌طوری‌که میانگین عملکرد در جمعیت حاصل از تلاقی پارسی × بک‌کراس زمستانه روشن، از 12.65 گرم در بوته به 10.03 گرم در بوته و در تلاقی دوم این مقدار از 12.93 گرم در بوته به 9.68 گرم در بوته کاهش یافت. والد پارسی در مقایسه با والد روشن افت عملکرد بیشتری از خود در اثر تنش کمبود آب نشان داد. بیشترین مقدار وراثت‌پذیری خصوصی محاسبه‌شده برای هر دو تلاقی به‌ترتیب متعلق به محتوای کلروفیل b (52%-52%)، مساحت سطح برگ (50%-50%) و محتوای کلروفیل کل (45% - 42%) در شرایط نرمال بود. در شرایط تنش کمبود آب نیز در جمعیت نخست بیشترین مقدار وراثت‌پذیری خصوصی متعلق به محتوای کلروفیل b (68%)، مساحت سطح برگ (%61) و محتوای کلروفیل کل (54%) و در دومین تلاقی مربوط به محتوای کلروفیل a (78%) و شاخص سطح برگ (56%) بود. مقدار بالای وراثت‌پذیری خصوصی برای این صفات حاکی از نقش بالای اثر افزایشی در کنترل آن‌ها و امکان وجود تنوع مناسب برای گزینش مستقیم می‌باشد.

Genetic analysis of physiological traits in bread wheat under normal and terminal water-deficit stress conditions

IntroductionWheat is the main source of nutrition for about 85% people of the world. On the other hand, drought is one of the most damaging abiotic stresses leading limitation to food supply in the worldwide and decreases crops yield more than any other environmental factor especially in Iran. Study of physiological reactions and traits in wheat could be useful in identifying effective mechanisms to increase resistance to undesirable environmental conditions and to promote yield performance under drought stress condition. The purpose of the present study was to investigate the genetic inheritance and type of gene action in the control of physiological traits in bread wheat to progress breeding programs in order to increase the yield under both normal and drought stress conditions. Materials and methodsGene action could be studied using the generation means analysis (GMA). Generation mean analysis was performed using Mather and Jinks method (1982). The seeds of six populations (P1, P2, F1, F2, BC1:1 and BC1:2) for each cross (totally 11 treatments) were planted in a randomized complete block design with three replications. The parental genotypes used in this study were: “Winter B. C. of Roshan”, “Parsi”, “Sistan”. The crosses, “Parsi × Winter B. C. of Roshan” and “Sistan × Winter B. C. of Roshan” were made in 20142015. The experiment was conducted under two normal and waterdeficit stress conditions in 20152016. Different traits including, grain yield, total chlorophyll content, chlorophyll a, chlorophyll b, leaf area index, leaf temperature, relative water content, stomatal conductance, persistence indicator and photosystem II maximum efficiency were measured. Broadsense inheritability was calculated according to following formulas; h_b^2 = [V_(F_2 ) – (V_(P_1 ) × V_(P_2 ))1/2] / V_(F_2 ) h_b^2 = (V_(F_2 ) – V_(F_1 )) / V_(F_2 ) h_b^2 = [V_(F_2 ) – (V_(P_1 ) × V_(P_2 )×V_(F_1 ))1/3] / V_(F_2 ) h_b^2 = (V_(F_2 ) – VE) / V_(F_2 )VE = [V_(P_1 )+ V_(P_2 )+ (2V_(F_1 ))] / 4 Narrowsense inheritability was calculated according to Warner (Warner, 1952) as follows:h2n=[2 VF2 (VBC2 + VBC1)/ F2Analysis of variance and mean comparison of the characters were performed using SAS Software. Generation mean analysis was carried out only for those traits that showed significant differences among generations. Results and discussionThe results showed that grain yield decreased in both of crosses due to waterdeficit stress. In general, “Parsi” showed a higher reduction in grain yield when compared to the “Winter B. C. of Roshan”. In normal condition of both crosses (“Parsi × Winter B. C. of Roshan” and “Sistan × Winter B. C. of Roshan”), the highest amount of narrowsense heritability (h_n^2 ) belonged to chlorophyll b content (52% 53%), leaf area index (5058%) and total chlorophyll content (4563%), respectively. In waterdeficit stress condition for the first population, the highest amount of narrowsense heritability (h_n^2 )belonged to the content of chlorophyll b (61%), leaf area index (54%) and total chlorophyll content (68%), and in the second cross it belonged to content of chlorophyll a (78%) and leaf area (56%). The differences among generation was not significant for grain yield in both crosses in different conditions except for the cross “Sistan× Winter B. C. of Roshan” in normal condition. The genetic analysis for this trait showed that the additive component was not significant but dominant component was highly significant which indicating that conventional selection may not be effective for the improvement of the trait and therefore for the selection for this trait suggested to be postponed to the later generation. ConclusionsThe high amount of narrowsense heritability for chlorophyll b content, leaf area index and total chlorophyll content illustrates that additive effects play a big role to control them. Therefore, selection method could be effective method to improve the mentioned traits in breeding programs.