Effects of Streptomycets on Growth and Mycorrhizal Colonization of Leek Root

It has been established that arbuscular mycorrhizal fungi (AM) as symbiont of plant roots improve their growth in nutrient poor conditions as well as stressful environments. There are evidences that the presence of some microorganisms including actinomycets or their metabolites، has provided the mass production of these fungi by stimulation of their spore germination percent and rate. In a pot culture experiment، leek plants (Allium ampeloprasum L.) were co-inoculated with Glomus intraradices and Streptomyces species (Streptomyces. sp، S. griseus and S. albogriseus) in a sterile sandy loam soil. At harvest، mycorrhizal colonization and frequency of fungal organs (hyphae and vesicles) in root، fresh and dry weights of root and shoot and also root and shoot P concentrations were measured. Results indicated that not only these species of Streptomyces promoted symbiosis formation، but they was also implicated in complementing the function of mycorrhizal fungus، including P acquisition and root and shoot growth of leek plant. All three species of Streptomyces significantly increased the percentage of mycorrhizal root colonization (p<0. 01) compared to the non- Streptomyces control. These increments were 63. 01% in S. sp، 56. 91% in S. albogriseus and 32. 27% in S. griseus compared to the control.. The fungal organs in roots were significantly increased at the presence of three Streptomyces species. Three species of Streptomyces، signficantly increased frequency of hyphae in roots up to 84. 1%، 78. 6% and 71. 67%، in Streptomyces. sp، S. albogriseus and S. griseus، respectively. Thus، S. sp، S. albogriseus and S. griseus enhanced the frequency of vesicles in mycorrhizal roots up to 43. 46%، 41. 33% and 29. 96%، respectively. Mycorrhizal leek roots inoculated with each species of Streptomyces significantly increased the fresh and dry weights of root، and dry weight of shoot، and root and shoot P concentrations.