ارزیابی تاثیر محلول‌پاشی پلی‌آمین‌ها بر رشد، ویژگی‌های میوه و عملکرد درختان پسته (pistacia vera l.) رقم ̕اکبری̔

کاهش عملکرد پسته ارتباط نزدیکی با اختلالات میوه و تنش های مختلف محیطی دارد. پلی آمین ها گروهی از تنظیم کننده های رشد گیاهی هستند که تاثیر مثبتی بر رشد و توسعه گل و میوه در برابر تنش ها دارند. بنابراین، هدف این مطالعه ارزیابی تاثیر پلی آمین ها در شرایط کم آبی محل آزمایش بر صفات رویشی، ویژگی های میوه و عملکرد درختان پرمحصول و کم محصول پسته رقم ̕اکبری̔ بود. برای این منظور، آزمایشی به صورت کرت های خرد شده در زمان بر پایه طرح بلوک های کامل تصادفی با سه تکرار و هفت تیمار شامل محلولپاشی پلی آمین های پوترسین، اسپرمیدین و اسپرمین در غلظت های صفر (شاهد)، 0.1 و 1 میلی مولار در دو مرحله زمانی تمام گل و دو هفته بعد از تمام گل در منطقه فیض آباد مه ولات استان خراسان رضوی در سال 1395 انجام شد. نتایج نشان داد که محلول پاشی پلی آمین ها در درختان کم محصول با وجود کاهش درصد پوکی تاثیر معنی داری بر عملکرد پسته نداشت. با این وجود در درختان پرمحصول، کاربرد این تنظیم کننده ها به ویژه پوترسین سبب کاهش ریزش میوه و افزایش شاخص سبزینگی، تعداد دانه در خوشه و عملکرد در مقایسه با شاهد شد. با توجه به نتایج همبستگی، تاثیر مثبت پلی آمین ها بر بهبود عملکرد در درختان پرمحصول عمدتاً به دلیل جلوگیری از ریزش میوه و افزایش تعداد دانه در خوشه بود. به طوری که میزان تولید در شاخه در تیمارهای پوترسین، اسپرمین و اسپرمیدین در غلظت 0.1 میلی مولار به ترتیب 46.2، 14.6 و 15.2 درصد و در غلظت 1 میلی مولار به ترتیب 38.7، 24.7 و 19.9 درصد در مقایسه با شاهد افزایش داشت. همچنین محلولپاشی پلی آمین پوترسین دو هفته بعد از تمام گل نتایج بهتری در افزایش طول شاخه در درختان پرمحصول نشان داد. به طور کلی، نتایج این آزمایش نشان می دهد که محلول پاشی پوترسین در مقایسه با اسپرمین و اسپرمیدین در شرایط کم آبی می تواند بر بهبود صفات رویشی و زایشی و در نتیجه عملکرد درختان پسته رقم ̕اکبری̔ موثرتر باشد.

Evaluation of the Effect of Exogenous Application of Polyamines on Growth, Nut Traits and Yield of ‘Akbari’ Pistachio Trees (Pistacia vera L.)

Introduction: Pistachio (Pistacia vera L.) is an important horticultural crop that has high economic value. Pistachio trees display some physiological disorders including abscission of inflorescence buds, fruit abscission, blankness, nonsplitting, early splitting and deformation of nuts. Unfavorable environmental conditions in most pistachio orchards and inadequate nutrition during the flowering time and after flowering has increased these problems in recent years. Polyamines such as putrescine, spermine and spermidine are some low molecular weight polycationic compounds that have been shown to play an important role as growth regulators in different stages of growth and development of buds, flowers and fruits and resistant plants to abiotic and biotic stress. Therefore, the objective of this study was to investigate the influence of polyamines in water scarcity condition on growth, nut traits and yield of ‘Akbari’ pistachio trees. Materials and Methods: The study was carried out in growing season 2016 in a pistachio orchard (Pistacia vera L. cv Akbari) located in Feyzabad, Mahvelat, Khorasan Province, Iran (34° 40´ N latitude, 58° 25´ E longitude, and around 1253 m above sea level). The climate of the experimental area was arid and semiarid. The mean annual precipitation was about 171 mm. The irrigation of orchard trees was at 36day intervals. The experiment was conducted as split plot based on a randomized complete block design with three replications and seven treatments including polyamines spray of Putrescine (Put), Spermine (Spm) and Spermidine (Spd) at concentrations of zero (control), 0.1 and 1 mM on “on” and “off” pistachio trees cultivar Akbari at twotime stages full bloom (FB) and two weeks after full bloom (2WAFB). Leaf chlorophyll index was recorded using the chlorophyll meter (SPAD502, Konica Minolta, Japan). Leaf area from fully expanded leaves was measured by Digital Leaf Area Meter (LI3100c). The length and diameter of currentyear shoots were measured at harvest time. The percentage of flower bud abscission and fruit abscission were calculated on marked shoots. The yield was calculated by weighting the total dried split nuts separated from each shoot. The data were subjected to analysis of variances (ANOVA) using the SAS software (SAS version 9.1). Difference between means was compared using the least significant difference test (LSD) at 5% level (p ≤ 0.05). Results and Discussion: Results showed that among the treatments, Put (0.1 and 1 mM) and Spm (0.1 mM) applied in the “on” trees significantly increased leaf chlorophyll index. Also, Put spray at two weeks after full bloom indicated better results in increase of length shoot in ‘on’ trees. All of the polyamines reduced fruit abscission in the “on” trees however, Put at 0.1 and 1 mM concentrations with 11.3 and 11.1% was more effective in decreasing the percentage of fruit abscission compared to other treatments. Fruit abscission of pistachio is assumed to be related to improper fertilization, the dominance of fruits in a cluster or abnormalities of reproductive organs. Polyamines have been suggested to improve fertilization, and subsequent embryo and fruit development. It also has been reported that common precursor of Sadenosylmethionine (SAM) needed for synthesizing both of PAs and ethylene. Thus, it seems that polyamines reduce the abscission of fruits by the improvement of embryo growth and development or by antagonism with ethylene, possibly by competing for Sadenosylmethionine (SAM). Our study indicated that all of the polyamines decreased the percentage of blank nuts in the “off” trees especially two weeks after full bloom. The results showed that Put (0.1 and 1 mM) and Spd (0.1 mM) were very effective in increasing number of nuts per cluster.  Number of nuts per 100 g, split nuts, and kernel percentage did not differ significantly among treatments. Yield variations were not significantly affected by polyamines in in the “off” trees, but in ‘on’ trees, polyamines of Put, Spm and Spd at 0.1 mM concentration by 46.2, 14.6 and 15.2% and at 1 mM concentration by 38.7, 24.7 and 19.9% increased yield compared to control, respectively. Given to correlation results, the positive effect of polyamines on yield improvement in ‘on’ trees was mainly due to the prevention from fruit abscission and enhancement no. of nuts per cluster. Conclusion: Results showed that application of polyamines treatments in ‘off’ trees only on blank nuts and in ‘on’ trees on leaf chlorophyll index, fruit abscission, No. of nuts per cluster and yield was effected. Foliar application of polyamines was more effective in improving traits of shoot length, leaf area and blank nuts two weeks after full bloom compared to full bloom. The results of this study showed that these plant growth regulators, especially putrescine, had the potential to improve growth, yield and reduce physiological problems of pistachio under unfavorable environmental conditions.