نوع مقاله : مقالات پژوهشی
نویسندگان
1 1. دانشجوی دکتری،گروه علوم باغبانی و مهندسی فضای سبز، دانشکده کشاورزی، دانشگاه فردوسی مشهد
2 گروه علوم باغبانی، دانشگاه فردوسی مشهد
3 مشهد-مرکز تحقیقات و آموزش کشاورزی و منابع طبیعی خراسان رضوی
چکیده
کلیدواژه‌ها
موضوعات
عنوان مقاله [English]
نویسندگان [English]
Introduction
Pear (Pyrus communis L.) belongs to the Rosaceae family and is native to Western Asia and Eastern Europe. Fire blight has five phases or five important stages of contamination, namely blossom blight, branch and leaf blight, fruit blight, main branches and trunk blight, and finally root blight. The USDA standard system is proposed and implemented by the United States Department of Agriculture (USDA). Additionally, the sensitivity of grafted cultivars to fire blight can be determined using the Gardner scale, which measures the percentage of blighted aerial parts of pear seedlings. The Erwinia amylovora bacterium obtains its energy by consuming carbohydrates, and an increase in carbohydrates in plant tissues leads to increased absorption of this bacterium. Furthermore, the cellular pH of the host plant also affects the growth and proliferation of fire blight bacteria, with the optimal pH range being between 5 and 10.
Material and mehod
Materials and methods
The rootstocks used in this experiment were Dargazi and Pyrodwarf, while the pear cultivars were Koshia and Dargazi. The experiment was conducted in both orchard and greenhouse conditions. In the orchard, a factorial experiment based on a randomized complete block design was carried out with five replications. The factors studied were the rootstocks (Dargazi and Pyrodwarf) and the pear cultivars (Koshia and Dargazi). In the greenhouse, a factorial experiment based on a completely randomized design was conducted with three replications. The factors studied were the rootstocks (Dargazi and Pyrodwarf) and the pear cultivars (Dargazi and Koshia). The Gardner scale was used to measure the severity of fire blight infection. Additionally, measurements of sucrose, sorbitol, and pH levels in the leaf tissue were taken The sucrose content in the leaf tissue of Koshia/pyrodwarf rootstock increased from day 0 to 6, reaching its highest level (10%) on the 6th day, and then decreased to 5% on the 12th day. In Dargazi/Pyrodwarf rootstock, the sucrose content increased from day 0 to 6, reaching its highest level (8%) on the 6th day, and then decreased to 5% on the 12th day. In Dargazi/Dargazi rootstock, the sucrose content increased from day 0 to 6, reaching its highest level (7%) on the 6th day, and 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, reaching its highest level (2%) on the 6th day, and then decreased to 1% on the 12th day. In Dargazi/Pyrodwarf rootstock, the sorbitol content increased from day 0 to 6, reaching its highest level (1.5%) on the 6th day, and then decreased to 1% on the 12th day. In Dargazi/Dargazi rootstock, the sorbitol content increased from day 0 to 6, reaching its highest level (1%) on the 6th day, and then decreased to 0.5% on the 12th day. On the other hand, the pH of the leaf tissue in Dargazi/Pyrodwarf rootstock remained constant at 6.2 from day 0 to 12. The pH of the leaf tissue in Dargazi/Dargazi rootstock was constant at 6.2 from day 0 to 6, and then increased to 7.4 on the 12th day. The data collected from both the orchard and greenhouse experiments were analyzed to determine the effects of rootstock and cultivar on fire blight resistance.
Results and discussion
Overall, the results of the experiment showed that the Koshia/Dargazi combination exhibited more resistance to fire blight compared to the Koshia/Pyrodwarf combination. The Dargazi/Pyrodwarf and Dargazi/Dargazi combinations were highly resistant to fire blight. The symptoms of fire blight were not observed in the Dargazi/Dargazi combination even 18 days after inoculation. The pH levels in the leaf tissue varied among the different combinations. The Koshia/Pyrodwarf and Koshia/Dargazi combinations showed fluctuations in pH levels, while the Dargazi/Pyrodwarf and Dargazi/Dargazi combinations had more consistent pH levels. The amount of sorbitol and sucrose sugars decreased slightly in the resistant Dargazi cultivar until 12 days after bacterial induction. In the Koshia/Pyrodwarf combination, the amount of these sugars decreased with the intensity of bacterial development in the tissues. However, in the Dargazi/Dargazi combination, the amount of sugars remained constant due to the lack of bacterial penetration and the cultivar's resistance to the disease. These findings suggest that using resistant rootstocks or inter-stocks can contribute to disease resistance in pear trees. The results of this experiment provide valuable information for researchers and growers in selecting appropriate rootstocks and cultivars to mitigate fire blight infection.
Conclusion
results showed that the Koshia/Dargazi combination had higher resistance to fire blight compared to the Koshia/Pyrodwarf, and the pH and carbohydrate content in the leaf tissue of the rootstock influenced the growth and proliferation of fire blight bacteria.The results of this study showed that there are different degrees of resistance to fire blight among the studied combinations, which indicates the existence of sufficient potential for the program to breed and improve pear to resist this disease. Dargazi cultivar has a very high degree of resistance to fire blight in both orchard and greenhouse conditions. In general, the resistant of Dargazi rootstosk has some effect of its resistance on the sensitive Koshia cultivar.
کلیدواژه‌ها [English]
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