Microbial consortia as an option for biocontrol of Stromatinia cepivora

Abstract

Stromatinia cepivora, the causal agent of white rot, is responsible for 60–80% of economic losses in onion and garlic crops. This work aimed to select biological control agents (BCAs) to control white rot. Ten microorganisms were tested for hyperparasitic activity on S. cepivora sclerotia in garlic (Allium sativum). Bioassays consisted of pots filled with sterile soil and 50 sclerotia in a plastic tulle bag. Four microorganisms were selected to compare their capability for degrade sclerotia on garlic. Our results showed that increasing degradation happened when Th034, Th035, Th003, and Bs006 were added to the pots containing garlic. Subsequently, three application techniques (seeds, seedlings at transplant, and seeds and transplant) were evaluated. Seven BCAs applied singly and in mixtures were evaluated in semi-field experiments for their ability to reduce white rot symptoms in onion plants in soil inoculated with 300 sclerotia per kilogram. The results indicated that efficacy was dependent on microrganism, mixture, and technique of application. The synergy factor showed that only two treatments have synergistic effects. In both cases, the mixture consisted of a strain of Bacillus and two species of Trichoderma (T. koningiopsis, T. atroviride) applied twice. In most cases, antagonistic interactions among BCAs were observed.