Managing tomato vine decline with soil amendments and transplant treatments: fruit yield, quality, and plant-associated microbial communities

Abstract

Tomato vine decline (TVD) disease complex results in fruit yield loss, but what soil management strategies might mitigate it? In commercial fields with a history of TVD, five approaches (soil organic amendments and transplant treatments) were evaluated for their impact on fruit yield, fruit quality, and microbial abundance or diversity at four site-years. One site-year had very high TVD pressure and high variability with no yield differences, thus efforts focused on the remaining site-years. Marketable yield was not different among treatments but numerically followed a trend similar to total yield. Amending soil with poultry manure delayed maturity (i.e., increased proportion of green fruit) and had the greatest total yield increases of 17.2%, congruent with decreased abundance of root pathogens (Verticillium dahliae, Rhizopicnis vagum). Microbial DNA fingerprinting data of rhizospheres, roots and (or) stems suggested treatments did not significantly shift the total diversity fungal nor bacterial populations, but the aforementioned pathogen loads were reduced with the application of organic amendments relative to the untreated control. While drenching tomato transplants with pseudomonad culture increased their presence in roots, pathogen load was not reduced relative to the untreated control. Overall, these results show that soil organic amendments were able to improve tomato total yield in two of four site-years without reducing fruit quality (i.e., soluble solids, pH, colour), perhaps, in part, due to their ability to suppress specific root pathogens in commercial fields.