Enhancing seedling emergence and plant growth of forage brassica with a Trichoderma bio-inoculant

Abstract

Forage brassicas occupy the largest area (250,000 ha) of cultivated crops in New Zealand (NZ) to supplement pastures both in the dairy and dryland farming systems. Forage yields are affected by poor crop establishment due to the increased susceptibility of brassica crops to Rhizoctonia solani, a soil-borne fungal pathogen causing damping-off and root rot. The effectiveness of a Trichoderma bio-inoculant (TBI) was evaluated in glasshouse experiments using potting-mix and field soils artificially inoculated with R. solani inoculum with kale variety "Gruner", forage rape variety "Interval" and turnip variety "Dynamo" as test crops. TBI treatment significantly increased seedling emergence of all the test crops. Regular monitoring of plant growth revealed that plants were healthier in the TBI treatment with lower incidence of wire-stem disease symptoms compared to controls. Increased seedling emergence resulted in sig­nificantly more shoot dry matter in the TBI treatment with kale and turnip plants, whereas the root dry matter was significantly higher in all the three forage brassicas tested. In the TBI treatment, visual observation of roots showed a marked increase in fine root growth in kale and forage rape plants, while in turnip, bulb growth was enhanced. On-going work is developing an appropriate seed-coating formulation that will allow TBI to be inte­grated into sustainable forage crop management prac­tices in NZ.