M. MADHAIYAN, P. SANTHANAKRISHNAN AND D. PRGATHESWARI
Abstract
Orchid mycorrhizal fungi is essential for germination of orchid seedlings in the field and for a few species, the fungus acquires all carbohydrates for the plant throughout the life of the plant. An attempt was made to study the effect of combined inoculation of orchid mycorrhizal fungi with phosphobacteria in pot culture experiment. Efficient orchid mycorrhizal strains were selected based on the symbiotic germination test viz., Rhizoctonia solani (MSK-01) and Rhizoctonia repens (MSK-02); phosphate solubilizing bacterial strains (Pseudomonas striata PS-1 and PS-2) were also selected. Samples were drawn at 30, 45 and 60 days after planting and analyzed for plant biomass, mycorrhizal colonization and nutrient status. The result revealed that combined inoculation of R. solani (MSK-01) and P. striata (PS-01) induced mycorrhizal colonization (26.98 % and active mycorrhizal colonization 18.59 c)/0) over uninoculated control (18.46 % and active mycorrhizal colonization 13.32 0/0). In addition, other parameters like shoot length (70.38 cm plant-9, root length (16.55 cm plant-'), plant biomass (2.11 g plant-1), chlorophyll content (Chl a- 0.478, Chl b- 0.306 and total Chl- 0.306 mg/g of leaf), plant nutrient (nitrogen-1.32 %, phosphorous-0.27% and potassium-1.84 %) and carbohydrate content (25.89 %) over uninoculated control. The combined inoculation of orchid mycorrhizal fungi with phosphobacteria significantly increased growth, nutrient uptake and carbohydrate translocation.