Growth chamber and greenhouse screening of promising in vitro fungal biological control candidates for the soybean cyst nematode (Heterodera glycines)

Authors: HAARITH, DEEPAK - University Of Wisconsin; KIM, DONG-GYU - University Of Minnesota; CHEN, SENYU - University Of Minnesota; Bushley, Kathryn

Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/20/2021
Publication Date: 4/23/2021
Citation: Haarith, D., Kim, D., Chen, S., Bushley, K.E. 2021. Growth chamber and greenhouse screening of promising in vitro fungal biological control candidates for the soybean cyst nematode (Heterodera glycines). Biological Control. 160:104635. https://doi.org/10.1016/j.biocontrol.2021.104635.
DOI: https://doi.org/10.1016/j.biocontrol.2021.104635

Interpretive Summary: The soybean cyst nematode (SCN) is a significant pathogen of soybean that causes the largest yield losses worldwide. Control strategies for the SCN are limited and identification of new biological control agents for integrated pest management is essential. This study evaluated the ability of 10 fungi shown to produce compounds in liquid filtrates that are toxic to nematode and 10 fungi that directly parasitized the eggs of the SCN in petri-plate assays to control reproduction of the SCN in more realistic growth chamber and greenhouse plant assays. Results showed that three isolates performed as well as several commercially available biological control products on the market at much lower spore application rates. This research identified promising candidate for development as biological control agents for this plant parasitic nematode.

Technical Abstract: The soybean cyst nematode (SCN; Heterodera glycines) is the most economically consequential pathogen of soybeans worldwide. Although biological control of SCN was proposed decades ago, only a few products are available on the market. Mining for new fungal biological control organisms and evaluating their potential to enhance integrated management of SCN is crucial. In this study, we evaluated 20 candidate biological control organisms in vivo that were selected out of a culturable mycobiome of over 5000 isolates based on their per-formance in in vitro assays. Of these isolates, labelled A through T, we identified three isolates, one Ilyonectria sp. (D), and two Purpureocillium sp. isolates (E and T), that significantly reduced SCN reproduction on a susceptible soybean variety (Sturdy) inoculated with both high and low levels of SCN eggs, compared to an untreated control, in a growth chamber cone-tainer assay. In a greenhouse pot assay, Purpureocillium isolates E and T also controlled nematode reproduction better than an untreated control and performed on par with the commercial fungal biological control agent, MeloCon® WG, which was applied at 41-fold higher concentration. In a second greenhouse assay, with higher nematode numbers, only isolate E performed as well as MeloCon® WG. This research identified promising candidate biological control agents of SCN that are as or more effective than existing products at much lower spore inoculation levels.