برآورد گرافیکی نحوه کنترل ژنتیکی عملکرد دانه و اجزای آن در لاین‌های S7 ذرت در شرایط نرمال و کمبود آب

عملکرد و اجزای آن در ذرت نمونه‌ ای از صفات کمی هستند. دانستن نحوه عمل و اثر متقابل ژن‌ها تعیین خواهد کرد که کدام روش به‌نژادی می‌تواند تاثیر عمل ژن را بهینه‌تر کند و نقش روش‌های به‌نژادی در تکامل گیاهان زراعی را روشن خواهد کرد. به منظور برآورد عمل ژن‌ها و وراثت‌پذیری صفات عملکرد دانه و اجزای آن، نتاج حاصل از تلاقی نیمه دی‌آلل پنج لاین s7 ذرت در نسل‌ f1 موردارزیابی قرار گرفتند. ژنوتیپ‌های مورد ‌بررسی در قالب طرح بلوک‌های کامل تصادفی با دو تکرار در دو شرایط نرمال (دور آبیاری 5 روز) و کمبود آب (دور آبیاری 10 روز) در منطقه کرمان، ایران در سال زراعی 96-1395 کشت شدند. صفات تعداد بلال، تعداد دانه در ردیف، تعداد ردیف دانه، تعداد دانه در بلال، طول بلال، وزن صد دانه و عملکرد دانه در بوته در دو شرایط نرمال و کمبود آب مورد ارزیابی قرار گرفتند. نتایج نشان داد که اثرات افزایشی و غیرافزایشی هر دو در کنترل صفات مورد مطالعه نقش داشتند. با توجه به نتایج گرافیکی تجزیه هیمن و نقش بیشتر اثرات فوق غالبیت در کنترل اکثر صفات در شرایط نرمال و کمبود آب، استفاده از پدیده هتروزیس و تولید ارقام هیبرید برای بهبود و اصلاح ذرت پیشنهاد می‌شود. همچنین برآورد وراثت‌پذیری عمومی بالا و وراثت‌پذیری خصوصی متوسط برای صفات مورد مطالعه نیز نشان دهنده امیدبخش بودن مواد ژنتیکی مورد مطالعه برای اصلاح و بهبود صفات تحت شرایط نرمال و کمبود آب بود.

Graphical estimation of genetic control of grain yield and its components in S7 maize lines under normal and water scarcity conditions

Introduction Maize (Zea mays L.) is considered as one of the most important cereals in the field of world production. Water stress due to water shortages and its various forms is one of the main and most common limiting factors of crop yield, especially in arid and semiarid regions of the world. Therefore, in corn, identification, selection and use of tolerant cultivars against drought stress in order to prevent the reduction of crop yield is considered as one of the most important and essential issues in breeding programs. In order to design and implement an effective and useful program, knowledge of the genetic control of the studied traits is essential the impact of environmental factors and the interaction between genetic and environmental factors. Among different methods of genetic analysis of quantitative traits, diallel analysis using Hayman method as an appropriate and efficient method for estimating the genetic structure of the populations in the relatively short time was considered by plant breeders. Therefore, the present study was conducted to evaluate the gene effects, heritability and the control of yield and its components in drought stress conditions compared to normal conditions in corn. In order to select suitable breeding methods and take an effective step in the production of high yielding maize cultivars. Materials and methods In order to estimate the gene action and heritability of important agronomic traits, five S7 maize lines in a 5×5 halfdiallel cross with F1 hybrids derived from them in a randomized complete block design with two replications in two normal conditions (irrigation intervals of 5 days) and drought stress (10 days irrigation) were cultivated at the Research Farm of Graduate University of Advanced Technology, Kerman, Iran in 2017. Number of ear, grain number per row, grain row number, grain number per ear, ear length, 100grain weight and grain yield per plant were evaluated in two conditions. The graphical analysis was carried out using the Hayman method and genetic parameters including additive variance (D), nonadditive variance (H1 and H2) and covariance of additive with dominance effects (F) were also estimated by Hayman’s proposed regression method. In order to carry out the diallel analyzes by Hayman method in two normal and drought stress conditions and combined analysis of variance was used SAS command. Results and discussion Combined analysis of variance showed that there was a significant difference between genotypes, environment and genotype×environment interaction for all studied traits, indicating the genetic differences between lines and corn hybrids. The simple effect of a for all traits, except for the number of ear and its interaction with the environment, was significant for all traits except number of ear, grain number per row and grain yield per plant which showed that additive effects play a role in controlling these traits and showed a different behavior in the two environments. The simple component b, which includes nonadditive effects, was significant for all traits, and its interaction with the environment was also significant for all traits. The significance of the interaction between a and b effects with the environment indicates the difference in the type of additive and nonadditive genes in both normal and drought stress conditions. Generally, the gene type for controlling traits and their gene action, potential of dominance and recessive genes in parents, and additive and dominance effects were different for most studied traits of this research in both normal and drought stress conditions. The graphical results of Hayman’s analysis showed the role of overdominance genes effects in controlling most traits in normal and drought stress conditions. Conclusions The results of this study showed that although genes with both additive and nonadditive effects played a role in controlling the traits, the contribution of each of these effects was different in controlling each of the traits. Also, the control of these traits was different in both normal and drought stress conditions, and the genes controlling these traits differed from environment to environment. The results of narrow sense heritability and Hayman graphic analysis of traits showed that these traits were controlled by the nonadditive gene effects. Therefore, it can be said that in order to breed and improve the genetic value of the population for these traits (yield and its components), the selection method will not be very successful, but it should use the phenomenon of heterosis and crossed the parents to produce hybrids.