بررسي كود زيستي مايكوگرين بر روابط آبي و راندمان توليد ريز غده سيب‌زميني در شرايط تنش خشكي

Evaluation of Biofertilizer “Myco-green” on Water Relation and Efficiency of Potato Minituber Production in Drought Stress Condition

به منظور بررسی كود زیستی مایكوگرین بر رشد، عملكرد و كیفیت ریزغده سیب‌زمینی در شرایط تنش خشكی پژوهشی به صورت فاكتوریل درقالب طرح كاملاً تصادفی و در چهار تكرار در شرایط گلخانه انجام شد. بدین منظور بستر كشت به نسبت 2:3 (پیت: پرلیت) تهیه و با نسبت وزنی 1 درصد با كود زیستی مایكوگرین مخلوط شد. تیمارهای آزمایشی شامل ریزغده¬های دو رقم سیب‌زمینی (آگریا و مارفونا) و سطوح آبیاری با سه دور 5، 8 و 11 روزه بودند. پس از برداشت، ریزغده‌ها به اندازه‌های مختلف تفكیك شده و درصد ماده خشك آن¬ها نیز اندازه‌گیری شد. نتایج نشان داد كه در تیمار شاهد ( دور آبیاری 5 روزه) گیاهان حاصل از ریزغده به طور معنی¬دار از مقدار نسبی آب برگ بیشتری نسبت به گیاهان در دو تیمار دیگر برخوردار بودند. اما گیاهان در دو دور آبیاری 8 و 11 روزه در مقایسه با شاهد پتانسیل اسمزی پایین¬تر و پرولین بیشتری داشتند و توانایی تنظیم اسمزی گیاهان با افزایش دور آبیاری با مصرف كود زیستی افزایش پیدا كرد. تفاوت معنی‌داری در میزان تولید ریزغده با اندازه متوسط و ریز در سه دور آبیاری مشاهده نشد. با این حال در تولید ریز غده درشت تفاوت تیمارهای آبیاری معنی¬دار بود. در دو دور آبیاری 5 و 8 روزه در مقایسه با تیمار 11 روزه به طور متوسط 62 درصد غده درشت¬تری تولید شد. در درصد ماده خشك ریز غده تولیدی سه سطح آبیاری وضعیتی مشابه داشتند. دو رقم سیب زمینی در مجموع واكنشی متفاوت در تولید ماده خشك ریزغده داشتند. در مجموع با نتایج این پژوهش مشخص شد كه استفاده از كود زیستی مایكوگرین در كشت ریزغده سیب‌زمینی در شرایط معمول آبیاری و حتی با اعمال تنش ملایم (افزایش طول دوره آبیاری به 3 روز)، سبب افزایش عملكرد كمی و كیفی تولید ریزغده در گیاهچه¬ها می¬شود.

Introduction Today biological fertilizers are suitable substitutes for chemical manure. Hence they can improve soil fertility in sustainable agriculture system (Mandal et al, 2007). Moreover, in some composition they are accompanied with plant growth promoting rhizibacteria (PGPR), namely Pseudomonas and some Bacillus species. These bacteria can improve growth rate of the plants by some physiological aspects namely, cidrophore acid production, increasing endogenously phytohormone and helping more phosphor absorption and fixation of biological nitrogen (Tilack et al., 2005). The symbiosis of mycorrhiza with plants confers numerous benefits to host plants including improved plant growth and mineral nutrient absorption, tolerance to diseases and stresses such as drought, temperature fluctuation, metal toxicity, salinity and other adverse conditions (Fortin et al, 2002. Ryan et al, (2003) and Smith and Reed, (2008).Mycorrhizal plants are capable of absorbing more water in lower potential of water as compared with non-mycorrhizal plants (Sanchez and Blanco, 2001). Micro propagation of potato by micro and mini tubers have been established for improving multiplication rate and possibility of reserving some more stock plants as germplasm. Multiplication of the minitubers already have been accompanied by lower establishment that causes low vigor and performance of the plant. This experiment was performedto study the effect of biological manure accompanied with mycorrhiza and plant growth promoting rhizobacteria on water relationship and vigor of the plantlets derived from minituber in water stress condition. Material and Methods Myco-green is produced by Peat grow company in Malaysia and has been spreading in floriculture, seed beds, vegetable crops, seedling plant of oil palm and many other plants. The experiment was performedatthe University of International Technology Mara Sarawak (UITM). As first step, soil bed composition was combined with peat and perlite (1:3 ratio). Then it was completely mixed by Mycogreenbiofertilizers by 1 percent of weight ratio. Mixed soil bed and biofertilizer were transferred to boxes. Minitubers of two potato cultivars (Agria and Marfona) were cultivated in the boxes arranged with 6×8 cm distance. The test was conducted in a factorial experiment based on completely randomized design with four replications. The factors included three interval irrigation regimes (5, 8 and 11 days) and two potato cultivars. The amount ofwater supplement according to their treatment was evaluated by weighing the boxes and was calculated as the amount of field capacity base. Fertile grow as a completed micronutrient had been mixed thoroughly in the soil bedby 1% weight proportion because myco-green didnot possess it. Some water relation traits such as leafosmotic potential, relative water content (RWC), osmotic adjustment and leaf proline content were measured. The method described by Bierman and Liderman (10) was used for root colonization assessment. Mini-tuber obtained from any plantlet was weighed, arranged in four groups including less than one gram, between one to three grams, between three to five grams and more than five grams. To assess mini-tuber dry matter of any replication, three mini-tubers were randomly selected and sliced to one mm thick. The first group of samples were weighed-and then placed inside the drying oven for 48 hours at a temperature of 85ºC. The dried samples were weighed again and mini-tuber dry matter percentage was calculated. Two-way analysis of variance (ANOVA) of the data was carried out using SAS software (v. 8.02, SAS Institute, Cary, NC) and the means were compared by the Duncan’s Multiple Range Test. Results and Discussions: Results- showed that application of myco-green biofertilizers had significant effect (p <0.01) on relative water content of the potato plantlets’ leaves bythree interval irrigation regimes in three phases. Interaction -between cultivar and interval irrigation regimes was not significant. 5 and 8 days interval irrigation regimes had more RWC and did not significantly differ with each other. the higher amount of RWC in two irrigation regimes can be correlated with colonization of mycorrhiza. In contrast, RWC was diminished in 11 days interval irrigation regime. We can conclude that although mycorrhiza was able to absorb more water by increasing water conductivity, but this ability is not limited and can be ultimate by critical threshold of water accessibility. Concentration of free proline amino acid was higherin plantlets treated by 8 and 11 days interval irrigation regimes in comparison with control regime. We can conceive that proline levels are correlated with changes of osmotic potential in the plant. Cultivated plantlets in 5 days interval irrigation regime donot confront the water stress. Therefore, donot take more signaling agent for induction of producing endogenous proline. Interval irrigation regimes of 5 and 8 days produced larger minituber size in comparison with 11 days irrigation regimes. Howeverthere were no significant differences amongthree interval irrigation regimes in production of the smallestminituber size. Dry matter of minituber was not affected by application of biofertilizer in three interval irrigation regimes. Addition of biofertilizer in this research was applied in three interval irrigation regimes,whereas there is no unapplied biofertilizer treatment in this experiment, so we cannot pretend that biofertilizerdoesnot affect the dry matter of minituber. Yet, there is considerable achievement that dry matter of minituber had the same levels in three irrigations regimes even by reducing much more water (11 days irrigation interval treatment). ConclusionsIt is concluded that Myco-green biofertilizer containing mycorrhiza and plant growth promoting rhizibacteria had considerable effect on growth vigor by adjustment of water stress through promoting mineral nutrients absorption and increasing osmotic potential capability. This ability could be different with intensity of water deficiency. There is more effect of biofertilizers in mild water stress as compared to severe water stress conditions.