Genetic control of root architectural plasticity in maize.

Stephanie P Klein,Rahul Bhosale,Kathleen M Brown,Shawn Kaeppler,Hannah M Schneider,Meredith T Hanlon,Andrew Warry,Eric A Nord,Jonathan P Lynch,Ian Dodd

doi:10.1093/jxb/eraa084

Abstract

Root phenotypes regulate soil resource acquisition; however, their genetic control and phenotypic plasticity are poorly understood. We hypothesized that the responses of root architectural phenes to water deficit (stress plasticity) and different environments (environmental plasticity) are under genetic control and that these loci are distinct. Root architectural phenes were phenotyped in the field using a large maize association panel with and without water deficit stress for three seasons in Arizona and without water deficit stress for four seasons in South Africa. All root phenes were plastic and varied in their plastic response. We identified candidate genes associated with stress and environmental plasticity and candidate genes associated with phenes in well-watered conditions in South Africa and in well-watered and water-stress conditions in Arizona. Few candidate genes for plasticity overlapped with those for phenes expressed under each condition. Our results suggest that phenotypic plasticity is highly quantitative, and plasticity loci are distinct from loci that control phene expression in stress and non-stress, which poses a challenge for breeding programs. To make these loci more accessible to the wider research community, we developed a public online resource that will allow for further experimental validation towards understanding the genetic control underlying phenotypic plasticity.

Highlights

Crop varieties are generally developed for specific environmental and management scenarios
Plastic responses to drought and environment varied by phene (Fig. 1) and genotype (Fig. 2) for all four root phenes measured [angle (ANGLE), lateral branching frequency (BF), average lateral root length (LL), and distance to the first lateral branch (DISTLAT)] (Table 1)
Most genetic loci associated with stress or environmental plasticity were distinct from loci controlling phenotypic expression in water-stressed or well-watered conditions (Figs 3, 4; Supplementary Figs S2–S4; Supplementary Tables S6–S10)

Summary

Introduction

Crop varieties are generally developed for specific environmental and management scenarios. Increasingly unpredictable growth environments due to climate change, decreasing freshwater availability, and rising costs of fuel and nitrogen fertilizer require the development of crop varieties that are resistant to abiotic stress and for increased production in marginal soils (Tebaldi and Lobell, 2008; Brisson et al, 2010; Woods et al, 2010; Sandhu et al, 2016). The occurrence of water deficit stress is likely to become increasingly frequent and unpredictable as a result of global climate change. Plasticity may be morphological, anatomical, and developmental, involve changes in resource allocation (Sultan, 2000), and is under genetic control

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