اثر پوشش‌گذاری خوشه بر میزان رسیدگی و کنترل عارضه آفتاب‌سوختگی در میوه خرما رقم مجول

خرما یکی از محصولات مهم در مناطق خشک خاورمیانه و شمال آفریقا است که در مناطق گرم و خشک جنوب ایران نیز تولید می شود. یکی از مهمترین عوامل کاهش کیفیت و ارزش تجاری میوه خرما عارضه آفتاب سوختگی در دوره رشد و نمو میوه است. بنابراین، این پژوهش به منظور بررسی اثرکاربرد پوشش های کاغذ کرافت، پارچه متقال مشکی، سفید، آبی، توری گلخانه سبز، پوشش حصیری و بدون پوشش (شاهد) در مرحله خارک بر میزان رسیدگی و بروز عارضه آفتاب سوختگی خرمای رقم مجول در قالب طرح بلوک های تصادفی با هشت تکرار در سال های 1399 و 1400 در کلکسیون ارقام خرما واقع در ایستگاه تحقیقاتی ام التمیر، پژوهشکده خرما و میوه های گرمسیری در اهواز، انجام شد. انتهای پوشش ها باز بود و تا زمان برداشت روی درخت باقی ماندند. نتایج این آزمایش نشان داد اثر سال بر وزن خوشه، درصد کیمری، خارک و خرما معنی دار بود. در سال دوم میانگین وزن خوشه ها (5/83کیلوگرم)، درصد کیمری (8/6درصد) و درصد خارک (28 درصد) بیشتر از سال اول بود، در حالیکه درصد خرما در سال اول (10/48درصد) بیشتر از سال دوم بود. درصد میوه های باقی مانده در مرحله کیمری در هنگام برداشت در خوشه های با پوشش متقال مشکی کمتر از سایر پوشش ها بود. در سال اول توری گلخانه سبز، متقال سفید و کاغذ کرافت به ترتیب موجب افزایش 9/81، 12/99و 11/37 درصدی رطب نسبت به شاهد شدند. روش پوشش گذاری تاثیری بر اندازه و وزن میوه نداشت. پوشش های مورد مطالعه موجب کنترل عارضه آفتاب سوختگی شدند. پوشش کاغذ کرافت (6/78درصد) سبب کاهش معنی دار درصد میوه های خشک شده نسبت به شاهد (9/93درصد) شد. پوشش های مورد مطالعه بر میزان پوسیدگی میوه تاثیر نداشتند. با توجه به نتایج این پژوهش، پوشش متقال مشکی و سفید در کنترل میزان پوسیدگی و عارضه آفتاب سوختگی خرما رقم مجول نسبت به سایر پوشش ها موترتر بودند.

effect of bunch bagging on ripening rate and control of sunburn disorder in date palm fruit cv. medjool

date palm is one of the important crops mainly grown in the arid regions of the middle east and north africa as well as in the southern warm and dry areas in iran. one of the most important factors that reduces the quality and commercial value of date fruit is sunburn disorder during fruit growth and development. therefore, this research was carried out to evaluate the effect of kraft paper, black, white, and blue cloth, green greenhouse netting, straw bag, and without bag (control) at the khalal stage on the ripening rate and sunburn incidence of cv. medjool using randomized complete block design with eight replication in in umm al tameir research station, date palm and tropical fruits research, ahvaz, in 2020 and 2021. the bags’ ends were open and remained on the trees until harvest. the results showed that the bunch weight, the kimiri, khalal and date fruits proportions were affected by year. in 2021, average bunch weight (5.83 kg), kimiri percentage (8.6%) and khalal percentage (28%) were more than 2020, while in 2020 the percentage of date fruits (10.48%) was more than 2021. the rate of kimiri at harvest was lower in black cloth than in others bags. in 2020, bunch bagging with green greenhouse netting, white cloth, and kraft paper increased rutab rate by 9.81%, 12.99% and 11.37%, respectively, as compared to control. bagging did not affect fruit size and weight. all kind of bags decreased the incidence of sunburn disorder. kraft paper bag significantly decreased the percentage of dried fruits to 6.78% as compared to control with 9.93%. the rate of fruit decay was not affected by bagging. considering the results of this research, it was concluded that black and white cloth bags were more effective in reducing sunburn disorder and fruit decay rate of palm date fruit cv. medjool. keywords: date palm, bunch weight, fruit weight, khalal, kimiri, rutab, tamar. introductiondate palm (phoenix dactylifera l.) is a monocotyledonous species of the arecaceae family widely grown in the arid regions of the middle east and north africa (kordrostami et al., 2022). recently, the production and cultivation of date cv. medjool as the most popular and expensive date has attracted attention of consumers in many countries. failure to ripe of some of the fruits is one of the most important reported problems of this palm date commercial cultivar, which reduces its marketable fruit yield and quality. in addition, the incidence of sunburn disorder decreases the quality of the fruit of date cv. medjool.to prevent losses due to biotic and abiotic factors and to produce quality fruits with less dependency on chemicals, several good agricultural practices (gap) have been examined around the world. among these good practices, preharvest bagging of fruit has gained popularity as an effective method in different parts of the world (fao, 2016). bagging affects fruit maturity and ripening. there are conflicting results in literature in this regard. harash and al-obeed (2010) reported that bagging bunches with black, white, blue, or yellow plastic bags accelerated fruits ripening of cv. succary and cv. khalas dates and stated that the blue color bags were more effective in accelerating the ripening of date fruits.kahramanoglu and usanmaz (2019) studied the effect of bagging on dates of cv. medjool and found that bagging with black and porous polyethylene bags increased the fruit-ripening rate. it has been shown that bunche bagging can reduce the incidence of some disorders, so this method is widely used in some countries to reduce sunburn disorder and fruit cracking (sharma, 2009). therefore, this research was carried out to assess the effect of bunch bagging on ripening and prevention of sunburn disorder incidence in palm date fruits cv. medjool. materials and methodsthis research was carried out to evaluate the effect of kraft paper, black, white, and blue cloth, green greenhouse netting, straw bag, and without bag (control) at the khalal stage on the ripening rate and sunburn incidence of cv. medjool using randomized complete block design with eight replication in in umm al tameir research station, date palm and tropical fruits research, ahvaz, in 2020 and 2021. the bags’ ends were open and on the trees until harvest. after harvest, bunch weight, kimiri, khalal, rutab, and, tamar proportions, length, diameter, and weight of fruit, and rate of sunburn disorder and fruit decay as well as dried fruits were recorded. combined analysis of variance was performed, based on randomized complete block design principles, using sas 9.4 software. tukey test was employed for means comparison at the 5% probability level. results and discussionthe results of this research showed that bunch weight, and proportions of kimiri, khalal, and tamar were affected by growing. in 2021, the average bunch weight (5.83 kg), kimiri percentage (8.6%), and khalal percentage (28%) were more than 2020 (3.61 kg, 5.36%, and 25.27%, respectively), while the percentage of tamar in 2020 (44.51%) was higher than in 2020 (34.03%). this difference can be attributed to the difference in weather conditions during two growing season. in general, the weight of bunches covered with different bags was higher than control. the results are consistent with the results reported by omar et al. (2014) regarding the increase in bunch weight with the application of bags. the proportion of kimiri at harvest time in kraft paper bags (10.21%) was higher than in the other bags with the lowest in black cloth bags (4.19%). in 2020, greenhouse netting (18.38%), white cloth (21.56%), and kraft paper (19.94%) bags significantly increased in rutab percentage as compared with control (8.57%). it can be stated that bagging (with the open-end bags) in this research did not affect fruit ripening rate of date cv. medjool, and weather conditions were the main factor. bagging did not affect fruit size and weight. in some countries, this method is widely used to reduce the sunburn disorder of date fruits. in this research, all kind of bags reduced the incidence of sunburn of fruits. in 2020, the proportion of dried fruits (14.24%) was higher than in 2020 (4.74%) and the kraft paper bag (6.78%) significantly decreased as compared to control (9.93%). the fruit decay rate was not affected by bagging. considering the results of this research, it was concluded that black and white cloth bags were more effective in reducing sunburn disorder and fruit decay rate of date cv. medjool. references fao. 2016. a scheme and training manual on good agricultural practices (gap) for fruits and vegetables. volume 1: the scheme-standard and implementation infrastructures. food and agriculture organization of the united nations. regional office for asia and pacific. bangkok, thailand. 122 pp.harash, m.m. and al-obeed, r. 2010. effect of bunch bagging colour on yield and fruit quality of date palm. american-eurasian journal of agriculture and environmental sciences, 7(3), pp.312-319.kahramanoglu, i. and usanmaz, s. 2019. preharvest and postharvest treatments for increasing the rate of ripening of date palm fruit (phoenix dactylifera l.) cv. medjool. progress in nutrition, 21(1), pp.215-224. doi: 10.23751/pn.v21i1.7817omar, a.d.e.k., al-saif, a.m. and ahmed, m.a.e.a. 2014. bagging of bunches with different materials influences yield and quality of rothana date palm fruit. journal of food, agriculture & environment, 12 (2), pp.520-522.