تاثیرتیمار بیولوژیک بذر Astragalus cicer با باکتری اندوفیت Bacillus subtilis بر نرخ جوانه زنی و بهبود شاخص قدرت رویشی گیاه

Chickpea milkvetch (Astragalus cicer) belong to the leguminous family is a useful plant with pasture feed value, high protein contain and digestibility. Low germination rate and poor stand establishment of seedlings prevented the mass production of A. cicer until now. Among the growth-promoting bacteria, endophytic isolates of Bacillus subtilis was considered by many researchers in biological treatment of seed, due to their establishment in plant tissue and their beneficial effect on plant metabolism. In this study, different isolates of gram-positive bacteria (from the genus Bacillus) were isolated from the nodules located in the roots of chickpea milkvetch (plants located in the field of Seed and Plant Registration and Certification Research Institute, Karaj). One of the isolates (Ye2) showed more than 99.5% similarity to the B. subtilis species based on the results of the 16S rDNA sequence homology with the known sequences in the NCBI genomic database. The plant growth promotion features of Ye2 were investigated and the effect of the biological treatment of A. cicer on seed germination rate and seedling vigor were analyzed based on the instructions of International Seed Testing Association. After surface disinfection, seeds treated with suspension of B. subtilis (Ye2) (108 CFU/gram seed), and the planted seeds were kept in controlled condition at 25°C. The treated seed germination rate were recorded regularly and after two weeks, vigor indices, plant length, root length, dry weight of seedlings obtained from treated and untreated seeds. The results of the present research showed that the Ye2 isolate had a high ability to produce phytase enzyme, ACC deaminase enzyme, auxin and has nitrogen fixation ability, so showed good potential in improving the vegetative characteristics of seedlings and seed germination. The seeds of A. cicer which treated with Ye2, showed increase in germination rate from 36% to 54% which equivalent to 1.5 times more than not treated seed. Also, the increasing of 1.27 times of the seedling length, 1.25 times of the stem length, and 1.26 times of the root length compared to the control showed the acceptable effect of seed treatment with the B. subtilis (Ye2) in improving the growth index of the Chickpea milkvetch. Although additional research to improve higher germination rate is a necessity for commercial seed cultivation and propagation.