اثر دو پایه نیمه‌پاکوتاه oh×f87tmو پیرودوارف بر جذب آهن و خصوصیات مرتبط با سبزینگی برگ برخی ارقام تجاری گلابی

از مهمترین شاخص ها در گزینش نهائی پایه های گلابی برای کشت در مناطق پرورش این محصول در کشور، خصوصیات مرتبط با جذب آهن و سبزینگی برگ و عدم بروز کلروز برگی در ارقام پیوند شده می باشد. بر این اساس، پژوهش حاضر با هدف ارزیابی قدرت جذب آهن کل و میزان آهن فعال و اثرآن بر روی خصوصیات مرتبط با سبزینگی برگ در چهار رقم تجاری گلابی روی دو پایه پیرودوارف و oh×f87tm در سال 1403 در ایستگاه تحقیقات باغبانی کمالشهر کرج اجرا شد. ارقام گلابی مورد بررسی شامل چهار رقم، پکهامز تریومف، اسپادونا، درگزی و لوئیزبون بودند. طرح آزمایشی به صورت فاکتوریل در قالب طرح بلوک های کامل تصادفی با سه تکرار با سه عامل پایه در دو سطح، رقم در چهار سطح و موقعیت برگ در دوسطح بود. نتایج بیانگر معنی دار بودن اثر پایه، رقم و موقعیت برگ روی صفات آهن کل، آهن فعال، کلروفیل کل،کلروفیلa و b و همچنین شاخص های رنگ سنجی برگ بود. عدم وجود تفاوت معنی دار بین دو پایه مورد بررسی در رابطه با میزان آهن کل و از طرف دیگر، وجود میزان بالاتری از محتوای آهن فعال، به میزان 86/2میلی گرم بر کیلوگرم وزن خشک برگ، درارقام پیوندی روی پایه oh×f87tm نشان دهنده مطلوبیت نسبی این پایه در خاک هایی با سطح متوسطی از آهک فعال بود. دامنه درصد آهن فعال برگ نسبت به آهن کل، در ارقام گلابی مورد بررسی از 19/76درصد تا 20/7درصد متفاوت بود. همچنین بیشترین محتوای کلروفیل کل در برگ های رقم درگزی و کمترین مقدار کلروفیل کل در رقم اسپادونا در مقایسه با سایرارقام مشاهده شد. پایه، رقم و موقعیت برگ بر شاخص های رنگ سنجی b*، a* وl* برگ اثرگذار بودند. حداقل شاخص a* و b* در ترکیب پیوندی رقم درگزی روی پایه oh×f87tm مشاهده شد، درحالی که این ترکیب پیوندی از نظر محتوای آهن و کلروفیل کل، بیشترین میزان را دارا بود. نتایج این پژوهش نشان داد که پایه  oh×f87tm 7از توانایی مطلوبی در مقایسه با تجاری پیرودوارف در رابطه با جذب و نگهداری آهن به فرم آهن فعال برخوردار بود.

effect of two semi-dwarf oh×f87tm and pyrodwarf rootstocks on iron absorption and chlorophyll related characteristics of leaves in some commercial pear cultivars

iron absorption, leaf chlorophyll content and tolerance to leaf chlorosis are among important chrachteristics in the final selection of pear rootstocks for cultivation in alkaline and semi-alkaline soils of iran. therefore, this study aimed to evaluate the total iron absorption potential, active iron content, and their impacts on leaf chlorophyll content in four commercial pear cultivars grafted on two oh×f87tm and pyrodwarf rootstocks. pear cultivars; cv. packham's triumph, cv. spadona, cv. dergazi, and cv. louis bonne were grafted on oh×f87tm and pyrodwarf rootstocks. the experiment was carried-out as factorial arrangements in randomized complete block design wsith three replications and three experimental factors; rootstock at two levels, pear cultivars at four levels and leaf position at two levels. results indicated significant effect of rootstock, cultivar, and leaf position on total iron, active iron, chlorophyll a, and b, total chlorophyll, and leaf colorimetric indices. active iron in the leaves of pear cultivars varied from 19.76% to 20.7% of total iron. the higher active iron content in the oh×f87tm rootstock (86.32 mg kg-1 dw) suggests its adaptability to moderate level of active lime in the soil. among the pear cultivars, cv. dergazi had the highest total chlorophyll content, while cv. spadona had the lowest. the rootstock × cultivar × leaf position effect on colorimetric indices, l*, a*, b*, and cv. dergazi cultivar on oh×f87 tm rootstock showing the lowest a* and b* indices and the highest iron and total chlorophyll content. keywords: pear, total iron, active iron, colorimetric index, chlorophyll content, spad index.introductionpear (pyrus communis l.) is among the five most important fruits in the world mainly due to its high adaptability to different climatic conditions. iran is one of the main centers of diversity of the genus pyrus in the world, and different cultivars of common pear belonging to the species p. communis l. are well adapted to the temperate climate of this region (abdollahi, 2010). accordingly, the cultivation of pear trees in iran has a history of several thousand years, and traditional orchards of this fruit tree have developed and improved over the past few decades (abdollahi, 2010; abdollahi, 2021). currently, one of the main components in the development and improvement of pear orchards is usage of semi-dwarf and dwarf rootstocks with adaptability to the climatic and soil conditions of the pear production areas in iran.adaptability tests of different pear cultivars and rootstocks demonstrated the impact of both on fruit yield, fruit quality and the final size of pear trees in commercial orchards (alizadeh fallahet al., 2022). during recent decades, pyrodwarf rootstock has been identified as a suitable rootstock for promoting early fruiting potential and reducing tree size in pear orchards established by commercial cultivars such as dergazi, louise bonne and spadona (abdollahi, 2021). additionally, oh×f rootstock series, paricularly oh×f217 and oh×f87, have shown promising results for fruit yield and quality. these impacts of rootstocks express in various ways, including crown volume, vigor, and growth habit induced in the grafted cultivars. the rootstocks also affect tolerance to the alkaline soils, which in turn affects the rate of iron absorption and transfer to cultivars and ultimately leaf chlorophyll content (fallahi et al., 2002).tthis study aimed to compare pyrodwarf and oh×f87tm rootstocks effect on iron absorption and leaf chlorophyll content in different grafted pear cultivars. materials and methodsthe trees were grafted on two rootstocks, pyrodwarf and oh×f87tm, with four fire blight tolerant commercial pear cultivars including; cv. packham's triumph, cv. spadona, cv. dargazi, and cv. louise bonne. the trees were seven years old at the time of evaluation. the experiment was factorial arrangements in randomized complete block design with three replications and tthere experimental factors; rootstaock at two levels, cultivar at four levels and leaf position at two levels. each experimental plot consisted of six trees of each scion/rootstock combination. sampling was conducted in august 2024 to assess the iron absorption characteristics; total iron and active iron, as well as leaf chlorophyll content and leaf colorimetric indices. leaf samples were collected from the lower and upper leaves of the shoots from the current season growth. these samples were then taken to the laboratory, where the leaf chlorophyll content was determined based on the spad index (spad, dch-52p minolta, japan). total iron conten was measured colorimetrically using orthophenanthroline reagent and read at 515 nm in a spectrophotometer. the chlorophyll a and b contents, and total chlorophyll content were measured using the spectrophotometric method with 80% acetone solvent and at 663 and 645 nm wavelengths. analysis of variance for data was performed using sas 9.2 software. the least significant difference (lsd) test was employed for means comparison at the 5% probability level. results and discussiondata analysis revealed that the effects of rootstock, cultivar, and leaf position were significant on the total iron, active iron, chlorophyll a, chlorophyll b, total chlorophyll contents, and leaf colorimetric indices. additionally, rootstock × cultivar × leaf position on these traits were significant, except for chlorophyll b. the lack of significant differences in total iron content between the two rootstocks, oh×f87tm and pyrodwarf, suggests that rootstock oh×f87tm is suitable for soils with moderate levels of active lime. this is supported by the slightly higher active iron content in rootstock oh×f87tm compared to pyrodwarf. comparison of colorimetric indices revealed significant difference between two rootstocks, oh×f87tm and pyrodwarf, in a*, b*, r, g, and b indices, with the exception of the l* index. in conclusion, the comparison between two rootstocks showed that oh×f87tm rootstock can be considered and recommended as a suitable rootstock, and even superior to pyrodwarf, for establishing semi-dwarf pear orchards in regions with soils of moderate levels of active lime. referencesabdollahi, h. 2010. pear: botany, cultivars and rootstocks. ministry of agriculture, tehran, iran. 210 pp. (in persian).abdollahi, h. 2021. comparison of bearing and yield efficiency of commercial pear cultivars on pyrodwarf semi-dwarfing rootstock. seed and plant journal, 37(4), pp.399-423 (in persian). doi: 10.22092/sppi.2022.356262.1254alizadeh fallah, m., yadegari, m., davarynejad, gh. and nemati, s.h. 2022. the rootstock and scion interaction effects on growth and bearing characteristics of young pear trees. journal of horticultural science, 36(2), pp.519-531. (in persian). doi: 10.22067/jhs.2022.73938.1112fallahi, e., colt, w.m., fallahi, b. and chun, i.j. 2002. the importance of apple rootstocks on tree growth, yield, fruit quality, leaf nutrition, and photosynthesis with emphasis on fuji. horticultural technology, 12(1), pp.38-44. doi:10.21273/horttech.12.1.38