Search

Elucidating the correlations among maize (Zea maysL.) brace-root traits and identifying the quantitative trait loci (QTL) that control the traits are important for genetic improvement of brace-root traits. Two maize inbred lines, Yi17 (well-developed root system) and Yi16 (poorly developed root system), an F2population derived from their cross containing 276 individuals, and an F2:3population containing 241 families were used to analyze the correlations among brace-root traits and determine the QTL for brace-root traits at Xiema and Hechuan in 2014 and 2015. All brace-root traits were highly significantly correlated with each other. In particular, brace-root diameter was highly correlated with brace-root fresh weight (r= 0.730), brace-root dry weight (r= 0.729), root fresh weight (r= 0.734), and root dry weight (r= 0.754). A total of 212 simple sequence repeat (SSR) markers were used to develop a genetic map based on the F2population. The total length of the genetic map was 1558.9 cM, with a mean interval of 7.35 cM between adjacent markers. Ninety-three QTL controlling the brace-root traits were detected in generations F2at Xiema in 2014 and F2:3at Xiema and Hechuan in 2015. However, only two consistent major QTL were identified in F2:3generation—qBRTN8b for brace-root tier number and qBRD8b for brace-root diameter. The qBRTN8b was located in the mmc0181 to bnlg1031 interval (bin 8.06) on chromosome 8, which explained 32.64% (at Xiema) and 16.18% (at Hechuan) of phenotypic variation. The qBRD8b was mapped in the umc2367 to umc1846 interval (bin 8.05) on chromosome 8, which explained 14.28% (at Xiema) and 10.41% (at Hechuan) of phenotypic variation. Moreover, three new important chromosomal regions harboring QTL for brace-root traits were detected—bins 5.04, 6.06, and 8.05 to 8.06. These results could provide a very important reference for evaluating root traits under field conditions and for fine mapping QTL of brace-root traits in maize.