Abstract
In this study, the unconditional and conditional QTL (Quantitative trait locus) analysis for chlorophyll contents (CC) at different development stages of maize were detected under N input (+N) and N stress (-N), using the composite interval mapping method with a 203 F2: 3 population derived from an elite maize hybrid cultivar: Nongda108 (Huang C ×Xu178), and a molecular linkage maps including 189 SSR markers. The results showed that the mean CC at the five development stages (bell stage, BS; florescence stage, FS; early grain filling stage, EGFS; mid-grain filling stage, MGFS; and later grain filling stage, LGFS) for parent Xu178 under -N and +N conditions were 54.12 and 55.76, and there were 1.80 and 2.40 higher than another parent Huang C, respectively. The average CC for the F2: 3 populations were 55.6 and 58.32, higher than the mean of their parents, and the variance range of CC in +N was smaller than that of -N. These results implied that the variance ranges for CC were affected by -N stress in some degree. Under -N and +N conditions, 2, 2, 1, 3, 1 and/or 2, 2, 2, 7, 1 unconditional QTL for CC were detected at the five development stages respectively, and the accumulative contribution of the detected QTL could explain 22.75%, 22.93%, 19.77%, 49.87%, 12.79% and/or 16.95%, 23.49％, 19.38%, 84.56 %, 13.38% phenotypic variances of CC, respectively. There was one conditional QTL identified for periods from BS to FS, from MGFS to LGFS and/ or from BS to FS, and from FS to EGFS under -N and +N conditions, these could explain 12.90%, 25.51% and/or 15.98%, 26.67% phenotypic variances of CC for each period, respectively. There were different spatio-temporal patterns for QTL expression of CC, especially for qchl4 and qchl5b, which are the two major QTLs in maize development.
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