بررسی روند انتقال و تاثیر گونه های مختلف عامل بیماری های لکه قهوه ای جو روی برخی صفات مرتبط با جوانه‌زنی

هدف از این پژوهش مقایسه آزمون بلاتر اسمزی و روش کشت در محیط کشت آگاردار برای ردیابی و شناسایی قارچ‌های عامل بیماری‌های لکه قهوه‌ای نواری و لکه توری در نمونه‌های بذری، ارزیابی تاثیر نوع و میزان آلودگی بذر روی برخی صفات مرتبط با جوانه‌زنی بذر و رشد اولیه گیاهچه‌ها و همچنین بررسی روند انتقال آلودگی‌ها و بروز بیماری‌ها در گیاهان حاصل از بذر می‌باشد. شناسایی عوامل بیماری‌زای قارچی بر اساس ویژگی‌های ریخت‌شناختی و آغازگرهای اختصاصی گونه انجام شد. بر اساس آزمون بلاتر اسمزی میزان آلودگی ردیابی شده در نمونه‌های بذری از صفر تا 19 درصد متغیر بود. در مجموع، 61 جدایه بر اساس ویژگی‌های ریخت‌شناختی و مولکولی متعلق به گونه‌های p. teres (38 جدایه) و p. graminea (23 جدایه) شناسایی شدند. نتایج آزمون بیماریزایی نشان داد که تمامی جدایه‌های pyrenophora spp. به دست آمده از بذر علایم لکه قهوه‌ای را روی گیاهچه‌های رقم ریحان ایجاد می‌نمایند. نتایج آزمون جوانه‌زنی استاندارد نشان داد که در میان نمونه‌های بذری ارقام مختلف جو مورد بررسی، اختلاف معنی‌داری از نظر شاخص‌های بنیه و جوانه‌زنی وجود دارد. نتایج حاصل از بررسی میزان انتقال بیماری‌ها نشان داد که میزان بروز بیماری ناشی از قارچ p. teres در محدوده 3.18 تا 11.94 درصد و میزان بروز بیماری ناشی از قارچ p. graminea در محدودۀ 1.06 تا 5.40 درصد متغیر بود. نتایج این پژوهش دیدگاه‌ جدیدی را درباره روند انتقال بیماری‌های بذربُرد لکه قهوه‌ای و تاثیری که روی شاخص‌های مرتبط با ویژگی‌های جوانه‌زنی ارائه می‌دهد که می‌تواند در بازنگری استاندارد ملی سلامت بذر جو مورد استفاده قرار گیرند.

transmission dynamics and the impact of barley stripe disease agents on seed germination and early seedling traits

background and objectivestripe diseases, caused by species of the genus pyrenophora, are among the most significant diseases affecting barley worldwide. these pathogens can be transmitted through seeds to the next generation, reducing seed quality and crop yield. as a result, the use of healthy, certified seeds represents a primary management strategy for improving seed quality and seedling health. this study aimed to compare different diagnostic methods for detecting stripe disease agents in seed samples, assess the transmission rates of stripe and net blotch diseases from seed to the next generation, and evaluate the effects of seed infection on several traits related to germination and early seedling growth.materials and methodsto identify pyrenophora species responsible for barley stripe diseases in seed samples of the sahand, goharan, and yoosef cultivars grown in lorestan (borujerd), east azerbaijan (bostan abad), alborz (karaj), and tehran (varamin) provinces, seeds were collected following the international rules for seed testing (ista). infected seeds were detected using osmotic and agar cultivation methods. fungal isolates obtained from the agar medium were identified and confirmed based on morphological characteristics and species-specific primers. to determine the disease index, a pathogenicity test was conducted on the barley cultivar rihane seedlings, which were artificially inoculated with pyrenophora isolates. subsequently, the effects of seed infection by pyrenophora spp. on traits related to seed germination, the transmission process, and stripe disease incidence in the next plant generation were evaluated.resultsthe results of the osmotic test indicated that the proportion of pyrenophora-infected seeds in samples collected from different fields ranged from 0% (no infection) to 19%. a total of 61 isolates were identified based on morphological characteristics and species-specific molecular markers, including p. teres (38 isolates, 62%) and p. graminea (23 isolates, 38%). the highest infection levels in seed samples were 8% for p. teres and 5% for p. graminea. pathogenicity tests showed that all pyrenophora spp. isolates obtained from seeds could induce varying levels of disease index in barley seedlings. germination and seed vigor indices varied among the seed samples, likely influenced by the barley cultivar and seed infection by seed-borne fungi, particularly pyrenophora spp. seed infection by pyrenophora isolates negatively affected germination percentage and seedling quality, depending on the pathogenicity level and prevalence of the isolates. the transmission rate of stripe disease from seed to the next-generation plant showed that disease incidence caused by p. teres ranged from 3.18% to 11.94%, while incidence caused by p. graminea ranged from 1.06% to 5.40%. natural infection by pyrenophora spp. also reduced seed yield in the tested barley cultivars, with yield losses ranging from 3.44% to 18.76% compared to uninfected control cultivars.discussionthe results of this study indicate that, due to a limited understanding of the effects of pyrenophora isolates on seed quality and cultivar response, accurately predicting seed yield and the incidence of stripe diseases in the next plant generation remains challenging. the presence of infection in seeds alone does not directly determine seed quality. instead, seedling growth indicators are influenced by the complex interaction between fungal isolate pathogenicity and environmental conditions affecting host plants. these findings provide new insights into the impact of pyrenophora-infected seeds on germination-related traits and the field transmission rate of stripe diseases. the outcomes of this study could contribute to revising national standards for barley seed quality assessment and certification.