Effect of Arbuscular Mycorrhizal (AM) Fungus (Rhizophagus Irregularis) Inoculation in Different Levels of Water Deficit on Minituber Production in Potato

The symbiotic relationship between arbuscular mycorrizae and plants can improve plant growth by increasing mineral nutrient absorption, tolerance to diseases and stresses such as drought, temperature fluctuation, metal toxicity, salinity and other adverse conditions. 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 has been accompanied by lower establishment that causes low vigor and performance of the plant especially in water stress conditions. This experiment was done to study the effect of arbuscular mycorrhiza fungus inoculation on vigor and performance of planlets derived from minituber in green house conditions.
Material and This experiment was conducted as factorial based on a randomized complete design with four replications. The treatments were irrigation levels (100%, 85%, 75% and 65% of field capacity) and two levels of culture medium inoculation (inoculation with Rhizophagus irregularis and non- inoculation). The amount of water supplement was evaluated according to their treatment by weighing the boxes and calculating the amount of field capacity base. The method described by Gonigle et al (1990) was used for root colonization assessment. Mini-tuber obtained from any plant was weighed, arranged in three groups. Two-way analysis of variance (ANOVA) was carried out using SAS software (v. 8.02, SAS Institute, Cary, NC).
Analysis of variance showed that in all minitubers the main effects of incubation with mycorrhiza, irrigation levels and their interaction were significantly different (p≤0.05). Minituber dry matter percentage showed a significant difference (p≤0.05) with mycorrhizal inoculation and interaction between mycorrhiza and irrigation levels. Means comparison showed that generally more minituber production in different sizes was accomplished by mycorrhizal treatments in all irrigation levels in comparison with non-inoculated ones. The most minitubers in different sizes were accomplished with inoculated and providing 85% FC water treatment. Inoculation of minitubers in 65% and 75% FC of irrigation levels did the same as the competitive situation with non-inoculated miniturbers in 85% and 100% of irrigation at the most traits related with quantity and quality of minituber production.
It is concluded that although mycorrhiza was able to promote growth and final yield of minituber production and multiplication rate, this ability is not limited and can be extended ultimately by critical threshold of water accessibility. Dry matter of minituber was affected by application of mycorrhiza in four irrigation regimes. In relation with minituber dry matter, it is conceived that mycorrhiza can affect the dry matter of minituber but irrigation levels must be remarkable in this situation. Generally, it is concluded that mycorrhiza had considerable effect on performance of planted minitubers 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.