تاثیر باکتری‌های حل‌کننده فسفات در تامین فسفر از سنگ فسفات و بهبود رشد دانهال‌های پسته (pistacia vera l.) در سطوح مختلف شوری آب آبیاری

استفاده از باکتری‌های حل‌کننده فسفات (psb) متحمل به شوری از روش‌های موثر در افزایش کارایی سنگ فسفات، تامین فسفر مورد نیاز گیاه و بهبود رشد آن در محیط‎های شور می‌باشد. به‌منظور بررسی نقش psb در تامین فسفر مورد نیاز دانهال‌های پسته در شرایط شور، آزمایشی ‌به‌صورت فاکتوریل در قالب طرح کامل تصادفی با سه تکرار در شرایط گلخانه‌ای انجام شد. فاکتورهای آزمایشی شامل psb در سه سطح [شاهد (psb0)، باکتری pseudomonas sp. 1 (psb1) و باکتری pseudomonas sp. 2 (psb2)]، سنگ فسفات در دو سطح (صفر و 30 میلی‎گرم فسفر از منبع سنگ فسفات) و شوری آب آبیاری در سه سطح (صفر، 5 و 10 دسی زیمنس بر متر) بود. نتایج نشان داد که شوری آب موجب کاهش وزن خشک اندام هوایی و ریشه، کلروفیل، کاروتنوئیدها، مقدار نسبی آب و شاخص پایداری غشای برگ و غلظت فسفر اندام هوایی و ریشه دانهال‌های پسته گردید. در مقابل، پرولین، قندهای محلول و سدیم با افزایش شوری آب در برگ دانهال‌ها انباشته شد. با توجه به نتایج، اگرچه کاربرد سنگ فسفات به‌تنهایی تاثیر چندانی بر شاخص‌های مورد مطالعه نشان نداد، امّا کاربرد ‌هم‌زمان آن با باکتری‌ها بیشترین نقش را در بهبود رشد دانهال‌های پسته ‌به‌ویژه در شرایط شور داشت. بیشترین مقدار وزن خشک اندام هوایی (1/89 گرم بر دانهال) و ریشه (1/59 گرم بر دانهال)، کلروفیل b (1/30 میلی‎گرم بر گرم وزن تر)، کاروتنوئیدها (1/35 میلی‎گرم بر گرم وزن تر)، قندهای محلول (59/1 میلی‎گرم بر گرم وزن تر)، پرولین (36/7 میلی‎گرم بر گرم وزن تر)، مقدار نسبی آب برگ (91/0 درصد)، شاخص پایداری غشا (84/0 درصد)، غلظت فسفر اندام هوایی (0/39 درصد) و غلظت فسفر ریشه (0/35 درصد) از کاربرد ‌هم‌زمان سنگ فسفات و باکتری‌ها (‌به‌ویژه سویه psb2) در شرایط غیرشور ‌به‌دست آمد. از طرفی، تلقیح با psb (هم ‌به‌صورت مجزا و هم همراه با سنگ فسفات) موجب کاهش تجمع سدیم در اندام هوایی و ریشه دانهال‌های پسته شد. ازاین‌رو، استفاده از باکتری‎های حل‌کننده فسفات با کارایی بالا و خصوصیات محرک رشدی مناسب، می‎تواند علاوه‎بر افزایش کارایی سنگ فسفات و تامین فسفر مورد نیاز دانهال‌ها موجب بهبود رشد و افزایش مقاومت آن‌ها به تنش شوری گردد.

the effect of phosphate-solubilizing bacteria in availability of phosphorus from rock phosphate and improving pistachio (pistacia vera l.) seedlings growth at different levels of irrigation water salinity

introductionphosphorus (p) is one of the most important nutritional elements of plants and it is necessary for the development of plant roots. due to the high cost of chemical fertilizers, it is important to use cheap sources such as rock phosphate (rp) to supply p needed by plants. the efficiency of rp is low and its use alone cannot supply the p required by the plant. one of the ways to increase the efficiency of rp is to use phosphate solubilizing bacteria (psb). considering the salinity of soil and irrigation water in many pistachio-growing areas of iran, the use of salt-resistant psb can increase their resistance to salt stress in addition to supplying the p required by pistachios. materials and methodsin order to investigate the role of psb in supplying the required p of pistachio seedlings under saline conditions, a factorial experiment was conducted in the form of a completely randomized design with 3 replications in greenhouse conditions. the factors included psb at three levels [control (psb0), pseudomonas sp. 1 (psb1) and pseudomonas sp. 2 (psb2)], rp at two levels (0 and 30 mg p from rock rp) and irrigation water salinity at three levels (0, 5 and 10 ds/m). the bacteria used in this study were able to produce acc-deaminase, indole acetic acid and dissolve tricalcium phosphate in vitro. for inoculation, inoculum containing each bacterium with a population of 108 cells/ml was prepared in the nutrient broth medium and each pistachio seed (p. vera l. cv. badami) was inoculated with 500 µl of bacterial inoculum. the plants were irrigated with non-saline water for four weeks and then with saline water until harvesting based on experimental treatments. during the growth period, the soil moisture of the pots was kept at about 80% of the field capacity by weight method. finally, shoot and root sampling was performed and various characteristics such as shoot and root dry weight, chlorophyll, carotenoids, proline, soluble sugars, rwc, msi and phosphorus as well as sodium concentrations were measured. analysis of variance of traits was performed using sas software and the means were compared using the lsd method with a probability level of p≤0.05. results and discussionthe results showed that water salinity decreased the dry weight of shoot and root, chlorophyll a, chlorophyll b, carotenoids, relative water content (rwc) and membrane stability index (msi) of leaf and p concentration of shoot and root of pistachio seedlings. auxin produced by bacteria can directly increase cell division and growth or indirectly increase acc-deaminase production. on the other hand, proline, soluble sugars and sodium were accumulated in the leaves of seedlings with increasing water salinity. according to the results, although the use of rp alone did not show significant effect on the studied indicators, its simultaneous use with psb had the greatest role in improving the growth of pistachio seedlings, especially in saline conditions. the highest amount of dry weight of shoot (1.89 g.plant) and root (1.59 g.plant), chlorophyll b (1.30 mg/g fresh weight), carotenoids (1.35 mg/g fresh weight), soluble sugars (59.1 mg/g fresh weight), proline (36.7 mg.g-1 fresh weight), leaf rwc (91 %), leaf msi (84%) and the p concentration of shoot (0.39 %) and root (0.35 %) was obtained from the simultaneous application of rp and psb (especially psb2) in non-saline conditions. the psb increase soil p availability by reducing of soil ph by release of protons and organic acids and mineralization by production of acid phosphatases. bacteria, in addition to increasing soil p availability, improve phosphorus uptake and chlorophyll content in plants by affecting root morphology and its development in soil. on the other hand, inoculation with psb (both separately and together with rock phosphate) reduced sodium accumulation in the aerial parts and roots of pistachio seedlings. conclusionunlike pistachio trees, the tolerance of pistachio seedlings to salt stress is low. according to the results, the salinity symptoms were visible in the pistachio seedling leaves at the water salinity level of 10 ds/m, which caused the drying of the lower leaves and the burning of the edges of the young leaves. on the other hand, although the application of rp alone did not have significant effect on increasing the tolerance of plants to salt stress, the simultaneous use of rp with psb increased growth, the accumulation of proline and soluble sugars, the concentration of chlorophyll and carotenoids, the amount of rwc and msi and p concentration of pistachio seedlings, especially in saline conditions. therefore, the use of psb can help the growth and establishment of pistachio seedlings under salinity stress conditions and increase the efficiency of rp and supply p needed by the seedlings.