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Effect of cultivar on biocontrol efficacy of Pythium in hydroponic tomato system

Liza DeGenring: University of New Hampshire

<div>Oomycete pathogens cause significant losses in greenhouse production due to their swimming zoospores and wide host range. Many greenhouse producers have utilized commercial biological control agents (BCA), in addition to chemical treatments, to protect plants from these pathogens. Few studies have evaluated the effect of cultivar on BCA colonization and disease suppression efficacy in horticulture crops. This research evaluated the effect of cultivar on biocontrol efficacy in a small scale tomato hydroponic system to identify IPM potential. We predicted that there would be a significant difference in efficacy of BCA between tomato cultivars. Ten cultivars, ranging from those currently used in commercial production to wild relatives, were screened for disease susceptibility using <em>Pythium</em> spp. inoculated at transplant. Four cultivars were selected and evaluated for differential biocontrol efficacy. Biocontrols were applied twice as a drench at transplant to rockwool blocks and at transplant to coco filled pots or rockwool slabs. Plants were challenged 3 days after application with <em>Pythium</em> spp. Root rot, plant height, and dry biomass were evaluated after 3 weeks. This experiment will provide initial data for future research analyzing the causal reasons for varying BCA performances between cultivars and substrates. Results from this research will be shared with growers and biocontrol producers in an effort to improve on-farm performance and increase adoption of biopesticides as plant disease management tools.</div>