Cereal Rye Allelochemical Interaction with Pythium

Iowa landscape
Practice: 
Nutrient Management

Title: Furthering our understanding of the interaction of cereal rye allelochemicals with Pythium species and their impact on corn in the cereal rye-corn production system

Location: Iowa State University Campus

Time Period: 2021 - Present

Research Team: Alison Robertson and Jyotsna Acharya

Project Description: The most prevalent cover crop used in the corn-soybean production system in Iowa is cereal rye (CR). Management of CR in field crop production system continues to evolve, for example, some farmers are growing CR longer (planting corn into standing green rye) to get more biomass and greater ecosystem services. However, there are challenges associated with greater CR biomass production including reduced corn growth and yield. Proposed reasons for this yield decline in corn are seedling disease and allelopathy.

We have consistently demonstrated a CR cover crop serves as a green bridge for soil-borne pathogens of corn that cause seedling diseases and yield reductions, and we hypothesize allelopathy may also play a role. Allelopathy is a complex process in which plants release chemical compounds that affect the growth and physiological processes, e.g. defenses, of other plants. Allelochemicals also affect plant-microbiome interactions. Recently, with funding from INRC, we demonstrated synthetic MBOA, an allelochemical produced by CR, and secondary metabolites from CR plants reduced corn shoot and root growth in vitro and caused more severe seedling disease when Pythium was present.

The infective propagules (inoculum) of Pythium are oospores, sporangia, zoospores. Their germination is stimulated by seed and root exudates. We hypothesize allelochemicals released from decomposing rye residue favor germination and/or activity of Pythium in the corn spermosphere facilitating increased infection of the seedling that results in poor vigor and corn yield reductions in the cereal rye-corn production system by favoring seedling pathogen-corn interactions and by affecting early corn growth and development. In controlled studies, we will determine the effect of rye exudates on the (i) germination of oospores and sporangia, and (ii) movement of zoospores of Pythium species, belonging to Clade B and F, in the presence and absence of corn seedling exudates.

Publications:

Acharya, J., Kaspar, T. and Robertson, A.E. 2021. Effect of 6-Methoxy-2-benzoxazolinone (MBOA) on Pythium species and corn seedling growth and disease. Plant Dis. https://doi.org/10.1094/PDIS-04-20-0824-SC

Funders: Iowa Nutrient Research Center