Root exudates drive root avoidance of maize in response to neighboring wheat

Background and Aims

Plant roots respond to soil nutrient availability, but also to the identity of neighbor plants, and root exudates play a role therein. However, how root exudates influence root behavior is not well understood.

Methods

A sequence of eight experiments was designed to investigate whether and how root growth and distribution of maize (Zea mays L.) was affected when growing with neighboring wheat (Triticum aestivum L.). We focused on the role of 6-methoxy-benzoxazolin-2-one (MBOA), an important allelochemical in root exudates.

Results

We found that maize roots distributed away from neighboring wheat roots but not from other roots. Root length of maize was reduced by 37%, 40%, and 64% when maize was grown with live wheat plants, with residuals of wheat root exudates, or when directly treated with wheat root exudates, respectively. MBOA concentration in root exudates of wheat/maize intercropping was 315% higher than in maize monoculture. The expression of IAA-related genes in maize roots was down-regulated by the MBOA treatment. MBOA addition decreased maize root length, but wheat root length was not affected under the same concentration.

Conclusions

Our findings demonstrate that root exudate MBOA is an important specific mediator in maize-wheat interspecific interactions, providing new insights into the design and management of sustainable intercropping systems.