Benefits of winter cereal rye cultivar selection in mitigating corn yield drag

Sep 2022


Winter cereal rye (CR) is the most popular species of cover crop grown in Iowa and supports agricultural sustainability. CR may be planted before either corn and soybean, however, the response of these cash crops to the CC varies, including a positive or no effect on soybean yield versus and often, a negative effect on corn yield.

Two factors that may play a role in reduced corn yields are allelopathy and seedling disease caused by Pythium spp. We demonstrated more severe seedling disease (root rot) was observed when corn was inoculated with Pythium spp. and grown in the presence of rye allelochemicals and root extracts. Levels of allelochemicals in CR can vary depending on the cultivar, growth stage of the CR, above ground biomass and growing conditions. Since reduced yields of corn following a CR occur across different fields and years, we hypothesize characteristics of a CR cultivar (biomass and/or allelochemical production) may affect the alleopathy-Pythium spp.-corn interaction.

In this research, we plan to investigate if corn seedling disease caused by Pythium species varies among CR cultivars due to differences in allelochemical production by each CR cultivar.


An improved understanding of how CR cultivars affect seedling disease and corn yield would lead to recommendations regarding the best cultivars to plant ahead of corn and thus improve best management practices for using cereal rye as a cover crop in corn-soybean production systems. More specifically, resesarchers plan to:

  1. Evaluate the effect of exudates obtained from different CR cultivars on corn seedling growth.
  2. Evaluate the effect of exudates obtained from different CR cultivars on the growth of Pythium species.
  3. Observe the interaction between Pythium spp. and exudates obtained from different CR cultivars on corn seedling growth and root rot development.
  4. Present research at professional meetings and conferences and field days.


For objectives 1-3, a plate assay will be used to study rye exudates and allelochemicals from five cultivars of CR (Serafino, Hazlet, Tayo, Yankee, and Elbon). The growth of corn (Obj. 1), Pythium species, (P. lutarium, P. oopapillum, and P. torulosum) (Obj. 2), and corn seedlings inoculated with Pythium spp. (Obj.3) will be evaluated on media amended with the allelochemical exudates from each CR cultivar. For objective 3, a cup assay will also be used. Each treatment (Pathogen alone, corn alone, Pathogen + corn) will be replicated six times and each experiment repeated twice.

Corn seedling growth parameters (emergence, radicle length, shoot length) and percent of seedling root rot of each seedling will be recorded and analyzed.

Award Number: 

Project Updates

Note: Project reports published on the INRC website are often revised from researchers' original reports to increase consistency.

December 2023


Key Research Questions

We hypothesized characteristics of a cereal rye cultivar (biomass and/or allelochemical production) would affect the biological values of cover crops as a conservation practice. We compared corn seedling disease caused by Pythium species among CR cultivars.

Key Findings

In general, crude extracts from all CR cultivars slowed pathogen growth and reduced corn coleoptile and radicle lengths. When corn was grown on media amended with crude extracts from five CR cultivars (Elbon, Hazlet, Serafino, Tayo and Yankee) and colonized with Pythium lutarium, corn growth was reduced and root rot severity increased compared with the check (no extract with pathogen).

Subsequently, a cup assay was used to further investigate the allelopathic effect of Elbon, Hazlet, and Serafino on corn seedling growth and root rot. Corn grown in cups into which each cultivar had been planted had shorter radicles and coleoptiles compared with the check (no CR), regardless of the CR cultivar. Results from this study suggest that allelochemicals released from decomposing CR vary among cultivars, and their interaction with Pythium spp. could affect seedling disease on corn. Consequently, choice of CR cultivar may be an important management decision to reduce the negative effects of CR on corn.

Project Activities

Four presentations.

Publications / Journal Articles

Acharya, J., and Robertson, A.E. 2023. Effect of allelochemicals from cereal rye cultivar and Pythium lutarium on corn growth and disease. PhytoFrontiers 3: 847-845

Leveraged Dollars


December 2022

During this project period:

Allelochemicals were extracted from five cereal rye cultivars (Serafino, Elbon, Hazlet, Tayo, and Yankee). A plate assay was used to assess the effect of the allelochemicals on the Pythium-corn seedling interaction.

When corn seedlings were grown on media amended with extracts from each cultivar and inoculated with P. lutarium, an effect of extracts was detected for coleoptile length, radicle length and root rot severity in run 1. Corn coleoptiles and radicles were shorter than the check (no extract but pathogen present) and did not differ among CR cultivars. Root rot severity increased on extract amended media inoculated with the pathogen (run 1) P=0.21 (run 2) compared to the check.

In run 1, the greatest root rot severity was detected with extracts from Elbon, Serafino and Tayo compared to extracts from Hazlet and Yankee. In run 2, extracts from Serafino cultivar had numerically greater root rot severity than Elbon and Hazlet.