Mapping QTLs for Root Architecture and Yield in Maize

In crops, the genetic control of root architecture variation in the field and its relationship with yield are incompletely known. A 75 introgression-line (IL) collection from the maize cross B73 x Gaspé Flint was previously shown to segregate for several agronomically important traits (Salvi et al. 2011, BMC Plant Biology). The aim of our study was to investigate the presence of genetic variation for root traits at the adult stage in the field, and its effect on grain yield. For this purpose, the IL collection was grown in a replicated field trial at two water regimes (well-watered, WW, and water-stressed, WS). Forty-four traits covering phenology, plant architecture, yield, and root architecture were analyzed. Root architecture was investigated by means of shovelomics coupled with software-assisted digital image analysis, for a total of > 1,000 analyzed root images. The stress imposed in the WS experiment resulted in significantly lower yield and longer anthesis-silking interval when compared with WW. In WS, statistically significant lower root dry weight and higher number of brace roots were also observed. Relatively high correlation values (up to r = 0.66) were observed between visually or manually scored root traits and corresponding traits based on software-based analysis. QTL analysis showed a complex genetic control for most root traits, and only limited overlap between root and yield or yield components QTLs.  We will also report on the results from two very large QTL meta-analyses for yield and root traits in maize. These studies should contribute to unveil the role of root architecture variation on maize yield. (The financial support of EU FP7 Water4Crops, grant agreement#311933 is gratefully acknowledged).