Utilization of Inoculum Produced On-Farm for Production of AM Fungus Colonized Pepper and Tomato Seedlings Under Conventional Management

Arbuscular mycorrhizal [AM] fungus inoculum may be used to produce colonized vegetable seedlings for outplanting. Success depends, in part, upon a nutrient regime in the greenhouse that is conducive to AM fungus hyphal growth and signalling/recognition events between host and fungus. Experiments were conducted to develop a fertilization regime conducive to colonization of tomato (Lycopersicon esculentum L.) and pepper (Capsicum annum L.) seedlings utilizing a mixed species inoculum of AM fungi produced on-farm in a compost and vermiculite mixture. The regulation of colonization by phosphorus nutrition in these crops was contrasted to that in bahiagrass (Paspalum notation Flugge). Bahiagrass had higher levels of colonization than tomato or pepper at all P levels tested (0.31 to 62 ppm). Colonization of the vegetable seedlings dropped to nearly zero at 31 ppm P and above while that of bahiagrass remained at approximately 20% of root length. However, colonization of pepper and tomato seedlings was above 10% of root length at the 0.31 and 3.1 ppm P additions. Another experiment with eight cultivars each of pepper and tomato demonstrated a significant cultivar effect upon colonization of roots by AM fungi. Plants were satisfactorily colonized when grown for 4 weeks in horticultural potting media amended 1:9 or 1:19 (v/v, on-farm inoculum:media) and fertilized with a solution containing 0.31 ppm P.