ارزیابی اثر پایه بر میزان مقاومت برخی ارقام گلابی پیوندی به بیماری آتشک

باکتری عامل بیماری آتشک (erwinia amylovora) یکی از بزرگترین چالش‌ها در تولید میوه گلابی است و فقدان روش‌های کنترل موثر، بر نیاز به ارقام مقاوم به این بیماری تاکید می‌کند. بنابراین، آزمایشات تعیین سطوح حساسیت برای ایجاد برنامه‌های اصلاح نژادی که مقاومت در برابر این بیماری را تضمین کند، ضروری است. این مطالعه با هدف تعیین تاثیر پایه بر میزان مقاومت ارقام گلابی پیوندی به بیماری آتشک و بررسی اثر انتقال مقاومت یا حساسیت به بیماری از پایه‌های مقاوم به ارقام گلابی با سنجش سیستم usda در باغات گلابی آستان قدس رضوی و باغات نیشابور با دو رقم گلابی (̓درگزی̒ و کوشیا̒) پیوند شده بر روی دو پایه (̓درگزی و ̓پیردوارف̒) اجرا شد، و مقیاس گاردنر نیز بر روی نهال‌های یکساله در گلخانه بررسی شد، همچنین مجموع قندهای سوربیتول، ساکارز و ph عصاره برگی در روزهای صفر تا 18 پس از آلودگی طی چهار مرحله اندازه‌گیری شد. با القا باکتری مقدار قندها از روز 6 تا 12 پس از آلودگی در رقم و پایه ̓کوشیا̒/ ̓پیردوارف̒ از 30 به 20 میلی‌گرم (33 درصد کاهش قندها) ولی در رقم و پایه ̓کوشیا̒/̓درگزی̒ از 35 به 25 میلی‌گرم (29 درصد کاهش قندها) و در دو رقم و پایه درگزی̒/درگزی̒ و درگزی/پیردوارف ثابت ماند. در مورد ph هم، در نهال‌ها با رقم کوشیا پیوند شده روی پایه درگزی نیز این روند مشاهده شد. به این ترتیب ph در روزهای صفر، 3، 6 و 12 به‌ترتیب برابر 5/5، 6/5، 5/3 و 5/2 اندازه‌گیری شد. این در حالی است که در بافت برگ‌های ارقام و پایه‌های ̓درگزی̒/̓پیردوارف̒ و ̓درگزی̒/̓درگزی̒ این مقدار به‌ترتیب 5/5 و 5/6 و این روند طی روزهای مختلف تقریبا ثابت بود. نتایج نشان داد که پایه درگزی تا حدودی اثر مقاومت خود را بر روی رقم حساس ̓کوشیا گذاشت، به‌طوری‌که میزان مقاومت رقم و پایه کوشیا/درگزی بیشتر از میزان مقاومت رقم و پایه ̓کوشیا/پیردوارف بود. بطور کلی طبق نتایج بدست آمده احتمال می‌رود که پایه مقاوم، مقاومت به بیماری آتشک را تا حدودی به ارقام حساس منتقل نموده است. بنابراین در برنامه به‌زراعی گلابی به‌منظور مقاومت به بیماری آتشک می‌توان از پایه مقاوم به بیماری آتشک استفاده کرد.

evaluating the effect of the rootstock on the resistance of some grafted pear cultivars to the fire blight disease

introductionpear (pyrus communis l.) is a cold-climate fruit tree belonging to the rosaceae family, and it is native to western asia and eastern europe. fire blight disease is caused by the gram-negative bacterium erwinia amylovora, and it is considered one of the most damaging and harmful diseases in pome fruit trees in cold and temperate regions worldwide. the most sensitive plant organ in pome fruit trees to this disease is flowers. fire blight disease has five important stages, from initial infection to the final death of the tree trunk. these five stages include blossom blight, fruit blight, leaf blight, main branches, and trunk blight, and finally, root blight. the first and most important stage of pathogenicity in fire blight disease begins in early spring under high humidity, causing the burning and death of the flower. materials and methodsthe rootstock used in this experiment were dargazi and pyrodwarf, and the cultivars studied were koshia and dargazi. the experiment was conducted in two conditions, orchard and greenhouse. in the orchard, a factorial experiment was carried out in a completely randomized block design with five repetitions. the factors studied were rootstocks (dargazi and pyrodwarf) and cultivars (koshia and dargazi). in the greenhouse, a factorial experiment was carried out in a completely randomized design with three repetitions. the factors studied were rootstocks (dargazi and pyrodwarf) and cultivars (dargazi and kosha). gardner scale was used to measure the severity of fire blight infection. in addition, the levels of sucrose, sorbitol, and ph in leaf tissue were measured. the sucrose content in the leaf tissue of  koshia/pyrodwarf rootstock increased from day 0 to 6 and reached its highest level (10%) on the 6th day, then decreased to 5% on the 12th day. in the dargazi/pyrodwarf base, sucrose levels increased from day 0 to 6 and reached its highest level (8%) on the 6th day, then decreased to 5% on the 12th day. in the dargazi/dargazi base, sucrose levels increased from day 0 to 6 and reached its highest level (7%) on the 6th day, then decreased to 4% on the 12th day. the sorbitol content in the leaf tissue of koshia/pyrodwarf base increased from day 0 to 6 and reached its highest level (2%) on the 6th day, then decreased to 1% on the 12th day. in the dargazi/pyrodwarf rootstock, sorbitol levels increased from day 0 to 6 and reached its highest level (1.5%) on the 6th day, then decreased to 1% on the 12th day. in the dargazi/dargazi rootstock, sorbitol levels increased from day 0 to 6 and reached its highest level (1%) on the 6th day, then decreased to 0.5% on the 12th day. on the other hand, the ph of the leaf tissue in the dargazi/pyrodwarf base remained constant at 6.2 from day 0 to 12 and increased to 7.4 on the 12th day.  results and discussionthe rootstock used in this experiment were dargazi and pyrodwarf, and the cultivars studied were koshia and dargazi. the experiment was conducted in two conditions, orchard and greenhouse. in the orchard, a factorial experiment was carried out in a completely randomized block design with five repetitions. the factors studied were rootstocks (dargazi and pyrodwarf) and cultivars (koshia and dargazi). in the greenhouse, a factorial experiment was carried out in a completely randomized design with three repetitions. the factors studied were rootstocks (dargazi and pyrodwarf) and cultivars (dargazi and koshia). gardner scale was used to measure the severity of fire blight infection. in addition, the levels of sucrose, sorbitol, and ph in leaf tissue were measured. the sucrose content in the leaf tissue of koshia/pyrodwarf rootstocks increased from day 0 to 6 and reached its highest level (10%) on the 6th day, then decreased to 5% on the 12th day. in the dargazi/pyrodwarf rootstock, sucrose levels increased from day 0 to 6 and reached its highest level (8%) on the 6th day, then decreased to 5% on the 12th day. in the dargazi/dargazi rootstock, sucrose levels increased from day 0 to 6 and reached its highest level (7%) on the 6th day, then decreased to 4% on the 12th day. the sorbitol content in the leaf tissue of koshia/pyrodwarf rootstock increased from day 0 to 6 and reached its highest level (2%) on the 6th day, then decreased to 1% on the 12th day. in the dargazi/pyrodwarf rootstock, sorbitol levels increased from day 0 to 6 and reached its highest level (1.5%) on the 6th day, then decreased to 1% on the 12th day. in the dargazi/dargazi rootstock, sorbitol levels increased from day 0 to 6 and reached its highest level (1%) on the 6th day, then decreased to 0.5% on the 12th day. on the other hand, the ph of the leaf tissue in the dargazi/pyrodwarf rootstock remained constant at 6.2 from day 0 to 12 and increased to 7.4 on the 12th day. the collected data from both orchard and greenhouse experiments were analyzed to determine the effects of rootstock and cultivar on fire blight resistance. conclusionthe results showed that the combination of koshia/dargaz had higher resistance to fire blight compared to koshia/pyrodwarf. additionally, the ph and carbohydrate content in the leaf tissue of the rootstock affected the growth and proliferation of fire blight bacteria. this study demonstrated varying levels of resistance to fire blight among the studied combinations, indicating significant potential for breeding and improving pear resistance to this disease. the dargazi cultivar exhibited very high resistance to fire blight in both orchard and greenhouse conditions. overall, the resistance of the dargazi rootstock contributed to the resistance of the sensitive koshia cultivar.