QTL Identification for Brace‐Root Traits of Maize in Different Generations and Environments. Issue 1 (12th October 2016) - Gu, Dongdong
Abstract : Elucidating the correlations among maize ( Zea mays L.) 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 F2 population derived from their cross containing 276 individuals, and an F2:3 population 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 F2 population. 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 F2 at Xiema in 2014 and F2:3 at Xiema and Hechuan in 2015. However, only two consistent major QTL were identified in F2:3 generation—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.