Weed presence altered biotic stress and light signaling in maize even when weeds were removed early in the critical weed-free period

Authors: Horvath, David; BRUGGEMAN, STEPHANIE - South Dakota State University; MORILES-MILLER, JANET - South Dakota State University; Anderson, James; Dogramaci, Munevver; CLAY, SHARON - South Dakota State University

Submitted to: Plant Direct
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/22/2018
Publication Date: 4/23/2018
Citation: Horvath, D.P., Bruggeman, S., Moriles-Miller, J., Anderson, J.V., Dogramaci, M., Scheffler, B.E., Hernandez, A.G., Foley, M.E., Clay, S. 2018. Weed presence altered biotic stress and light signaling in maize even when weeds were removed early in the critical weed-free period. Plant Direct. Available: https://onlinelibrary.wiley.com/doi/abs/10.1002/pld3.57.

Interpretive Summary: Weeds reduce crop yield even if they are removed early in the growing season. We investigated which genes were turned on or off when weeds were present in corn under field conditions through the V4 stage and the V8 stage of development (early and late in the critical weed free period – the time that weeds have their greatest impact on crop yields). We identified numerous genes that were turned on or off consistently, over two growing seasons, when corn was competing with two different weeds. We determined that the changes in gene expression appear to be related various physiological and signaling processes including oxidative stress, various hormones, nutrient deprivation, and light and biotic stress signals. Most importantly, we determined that even if weeds were removed early in the critical weed free period, lingering effects on biotic stress and light signaling remain at least through the V8 stage. Both of these signals have been associated with reduced plant growth. This work provides several processes that can be targeted to help make plants more weed tolerant to reduce herbicide use.

Technical Abstract: Weeds reduce crop yield even when there is no competition for resources. A phenomena known as the critical weed-free period (CWFP), which occurs early in the crop’s life cycle, is the essential interval when weed presence can reduce crop growth and yield. Even when weeds are removed after the CWFP, crop growth and yield are not recoverable. In this study, we used RNAseq technology to analyze the transcriptome of field-grown hybrid maize at the end of the CWFP (V8) with or without the presence of weeds (velvetleaf or canola) during the CWFP in two consecutive years. Additionally, we compare the transcriptome of field-grown hybrid maize at V8 following weed removal at V4 to identify genes and pathways that are effected long-term by weed presence through the early CWFP. Physiological differences associated with altered photosynthetic processes, hormone signaling, nitrogen use and transport, and biotic stress responses were identified. Even when weeds are removed early in the CWFP, carbon:nitrogen supply imbalance, salicylic acid signals, and growth responses remain altered at V8. These underlying processes and a small number of developmentally important genes are potential targets for decreasing the maize response to weed pressure. Expression differences of several novel, long non-coding RNAs resulting from exposure of maize to weeds during the CWFP were also observed, and could open new avenues for investigation into the function of these transcription units.