برآورد پارامترهای ژنتیکی و تجزیه عاملی ویژگی‌های مورفولوژیکی و بیوشیمیایی ژنوتیپ‌های f2:4 برنج (.oryza sativa l) در مرحله جوانه‌زنی تحت شرایط شوری

تنش شوری موجب کاهش عملکرد گیاه برنج (oryza sativa)؛ غذای نیمی از مردم جهان، می‌گردد. به‌منظور ارزیابی پارامترهای ژنتیکی برخی از ویژگی‌های گیاه برنج در مرحله جوانه‌زنی به‌عنوان عاملی مهم‌ در استقرار مطمئن گیاهان، تعداد 117 لاین f2:4 به‌ همراه والدین تلاقی (موسی‌طارم و 304)، در دو آزمایش ‌تنش شوری (8 دسی‌زیمنس بر متر) و بدون تنش، به‌صورت جداگانه در قالب طرح بلوک‌های کامل تصادفی با سه تکرار در دانشگاه یاسوج در سال 1395 کشت گردیدند. پرولین محلول ساقه‌چه بیشترین تنوع ژنتیکی را در هر دو حالت تنش و بدون تنش داشت و پروتئین و قندهای محلول در رده‌های بعدی بودند. ژنوتیپ‌ها کمترین ضریب تنوع ژنتیکی را در هر دو حالت تنش و بدون تنش برای درصد جوانه‌زنی نشان دادند. بالاترین میزان وراثت‌پذیری در شرایط تنش و بدون‌تنش به ویژگی‌های پرولین، پروتئین و قندهای محلول تعلق داشت. بیشترین همبستگی فنوتیپی در شرایط بدون ‌تنش، مربوط به طول ریشه‌چه با شاخص بنیه طولی گیاهچه (0.75) و وزن خشک ساقه‌چه با شاخص بنیه وزنی گیاهچه (0.75) و در شرایط تنش بین سرعت جوانه‌زنی با شاخص بنیه طولی گیاهچه (0.80) دیده شد. بر اساس چرخش واریمکس در شرایط بدون تنش، پنج عامل بخش هوایی گیاهچه، بخش زیرزمینی گیاهچه، شاخص‌های جوانه‌زنی، خصوصیات فیزیولوژیکی و پروتئین کل با 74 درصد مجموع واریانس توجیهی و در شرایط تنش شش عامل موثر بر ویژگی‌های مورفولوژیکی، ریشه‌چه، وزن گیاهچه، قندهای محلول، پرولین و پروتئین کل با 78 درصد مجموع واریانس توجیهی شناسایی شدند. به‌طورکلی نتایج این پژوهش نشان داد که می‌توان ویژگی‌های پرولین و قندهای محلول گیاهچه و همچنین طول ساقه‌چه، وزن تر و خشک ساقه‌چه و درصد و سرعت جوانه‌زنی را به‌عنوان شاخص‌های موثر در گزینش ژنوتیپ‌های متحمل شوری برنج در مرحله جوانه‌زنی مورداستفاده قرارداد.

Genetic parameters estimation and factor analysis of morphological and physiological characteristics of F2:4 rice (Oryza sativa L.) genotypes in germination stage under salinity conditions

IntroductionSalinity stress greatly affects crop yields especially in arid and semiarid climates. The reaction of rice plants; with a special situation among other crops for supplying human nutrition, to salinity varies in different growth stages. Salinity tolerance in plants is a complex process in which morphological changes, physiological and biochemical processes are involved. In order to study the reaction of rice plants to salinity conditions and identification of tolerant genotypes, it is recommended to evaluate the salinity effects at salinity sensitive stages such as germination stage. The use of genetic diversity in crops is one of the most important interests of breeders in understanding the strategies for crops improvements. The aim of this research was to, estimate the genetic diversity of evaluated traits, study the effect of salinity on various morphological and physiological characteristics in the rice germination stage, determine the relationship between traits, and to identify the traits that affect the indirect selection of tolerant genotypes to salinity. Materials and methodsOne hundred seventeen F2:4 generation lines; obtained from the cross between Mousa Tarom and 304 rice genotypes, were cultured in two separate experiments; with and without salinity stress, in a randomized complete block design at the Faculty of Agriculture, Yasouj University. The seeds were placed in petri dishes in germinator at 25 ± 3 ° C. The number of germinated seeds of each genotype was counted during 14 days, and the seed length and weight vigor, germination percentage, seed germination rate, as well as the morpho physiological characteristics of rootlet and shootlet length, rootlet fresh and dry weight, shootlet fresh and dry weight, Leaf proline, total soluble sugars and leaf protein content were evaluated. Results and discussionIn both the salinity stress and nonstress conditions, the phenotypic coefficient of variation (CVp) was larger than the genetic coefficient of variation (CVg) for all measured traits. Leaf proline, total protein and soluble sugars had the highest CVg in both the stress and nonstress conditions, indicating a wide diversity of the evaluated genotypes. The genotypes showed the lowest CVg and CVp under both the conditions for germination percentage. So, it can be claimed that the genotypes were not significantly different in their reaction to environmental variations.Proline heritability was 98% in both the salinity conditions. The heritability of protein content in stress condition (86%) was about 13 percentage points lower than nonstress (99%). Salinity stress increased 6 percentage points of soluble sugars (98%) compared to nonstress condition. Salinity stress also increased the heritability of germination percentage, shootlet length, shootlet fresh weight, rootlet fresh weight, and shootlet dry weight and Seedling length vigor index compared to nonstress condition. In nonstress condition, the highest positive and significant correlation was found between rootlet and Seedling length vigor index, and between shootlet dry weight and weight vigor index. In stress conditions, the highest correlation was observed between rootlet length and rootlet dry weight. Also, a significant correlation was observed between the characteristics of the Seedling length vigor index with rootlet dry weight, rootlet and shootlet fresh weight, germination percentage and rate in salinity stress condition. Rootlet dry weight with germination percentage, rootlet length and shootlet length showed a positive and highly significant correlations. No significant correlation was seen between soluble proline, total protein content and soluble sugars in germination stage.On the basis of principal component analysis, in nonstress, and salinity stress conditions 5 and 6 factors were identified, respectively, which explained 74% and 78% of the diversity of the total data. In nonstress conditions, the first factor explained 33.92% of the variation, in that, traits such as shootlet length, shootlet fresh and dry weight and seedling weight vigor index had the highest effect with the positive direction. In stress condition, the first factor explained 32.2% of the total variation in which the shootlet fresh weight and length, germination percentage and germination rate, and Seedling length vigor index had the highest positive effect. ConclusionDifferent lines and varieties of rice show different responses to different environmental stresses, which evaluation of such a reactions are of particular importance for breeders. Leaf soluble proline, protein and soluble sugars had the highest genetic variation in both the stress and nonstress conditions. These conditions indicated that selection for soluble sugars, proline, and leaf total protein was promising, and their high heritability suggests that the traits in question are more likely to be transmitted to the offspring. Therefore, they can be used in breeding programs for creation of genetic diversity, hybridization and selection. Based on the results of factor analysis, shootlet fresh weight and length can be used as an effective feature in the selection of salt tolerant genotypes in both stress and nonstress conditions at germination stage.