Multiple brace root phenotypes promote anchorage and limit root lodging in maize

Abstract

A changing global climate brings increasingly prevalent and severe storms that threaten crop production by imparting mechanical stresses. Plant failure due to mechanical stress is termed lodging and in the United States, yield loss due to lodging has been estimated at 7-25% for maize (Zea mays). In maize, the presence of specialized aerial brace roots has been shown to increase anchorage and root lodging resistance. However, beyond scoring for presence, there have been limited attempts to define the brace root phenotypes that optimize anchorage. This study reports variable root lodging and plant biomechanics in a population of 52 maize inbred lines. To quantify the variation in brace root phenotypes within this population, a semi-automated phenotyping workflow was developed. These empirical measurements were integrated into predictive random forest models to demonstrate that brace root phenotypes can classify root lodging incidence and plant biomechanics. The prediction accuracy of these models is driven by multiple brace root phenotypes suggesting that anchorage can be optimized by the manipulation of multiple functional traits. Plant height has been previously associated with lodging susceptibility yet the inclusion of plant height as a predictor does not always improve prediction accuracy. Previously, brace root node number has been shown to be genetically linked to plant height and here we show that additional brace root phenotypes are linked to plant height but with opposing effects on root lodging susceptibility. Together these data define the important brace root phenotypes that predict root lodging resistance and demonstrate the need to uncouple the linkage between plant height and root traits for the development of climate resilient crops.

Genome-wide association study reveals the genetic basis of brace root angle and diameter in maize

“…However, Sharma and Carena (2016) reported that there was no correlation between plant height and root lodging during natural root lodging events. Notable, Hostetler et al (2021) described the low positive correlations between brace root phenotypes and plant height, and analyzed their opposing effects on lodging susceptibility. The taller plants are susceptible to lodging, but stronger brace roots provide them with more lodging-resistance.…”