| The flowering time and tassel-related traits are two types of important agronomic traits in the process of maize breeding for maize stability and adaptability. Therefore, studies on genetic backgrounds and mechanisms of these traits may give an important clue for the marker-assisted selection (MAS). Totally 230 and 235 F2:3 families derived from Qi319xHuangzaosi population (Q/H) and Ye478xHuangzaosi population (Y/H), respectively, were phenotyped under six different environments (2007-Beijing,2008-Beijing,2007-Henan,2008-Henan,2007-Xinjiang, and 2008-Xinjiang). QTLs controlling four flower-related and two tassel-related traits of maize were detected by using the inclusive composite interval mapping method (ICIM). Meanwhile, QTLNetwork v2.0 was used to analyze epistasis among QTLs and QTL by environment interaction (QEI). The QTLs which were observed to be consistent in different environments or genetic backgrounds would be useful for precise mapping and postional cloning. The main results were as follows:1. Two F2:3 populations Qi319xHuangzaosi and Ye478xHuangzaosi which contained two 230 and 235 F2:3 families, respectively were constructed for mapping, and two genetic linkage maps containing 194 and 159 SSR markers were constructed for Q/H and Y/H, apart. The Q/H map spanned a total of 2493.7 cM with an average interval of 12.85 cM. Among these markers,63 (32.5%) markers showed the genetic segregation distortion (P<0.05). The Y/H map spanned a total of 3168.99 cM with an average interval of 20.19 cM, and 59 (32.8%) SSR markers showed the segregation distorition.2. With the inclusive composite interval mapping method (ICIM), QTL were detected for 4 flowering and 2 tassel-related traits under different environments. Based on single environment's analysis, a total of 115 QTLs (containing 85 QTLs in Q/H and 30 QTLs in Y/H) controlling the flowering-related traits,40 QTLs controlling the tassel primary branch number (TPBN, containing 23 QTLs in Q/H and 17 QTLs in Y/H) and 11 QTLs controlling the tassel weight(TW, containing 10 QTLs in Q/H and 1 QTLs in Y/H) were identified in the two populations. For flowering-related traits,36 major QTLs were detected (containing 24 QTLs in Q/H and 12 QTLs in Y/H), and two and one important QTL which expressed among multi-environments with the PVE≥10% were found in Q/H and Y/H, respectively, i.e. the QTLs located in the umc1562-bnlg1651 marker interval on chromosome bin 8.05 were controlling DTT and DTP, the QTLs identified in phi062-umc1115 on bin 10.04 were controlling DTT, DTP, DTS and ASI, and the QTLs for DTT, DTP and DTS were detected in nc030-umc2166 interval on bin 3.04-3.05. The numbers of major QTLs for TPBN and TW were 5 (3 QTLs in Q/H and 2 QTLs in Y/H) and 2 (1QTL in Q/H and the other in Y/H), respectively. Especially, the QTL for TPBN and TW detected in the umc2160-umc1016 interval on chromosome bin 7.01-7.02 and the QTL for TW identified in bnlg1094-bnlg1579 on bin 7.02-7.03 were detected as the important QTL regions for Q/H population.3. QTLxenvironment interaction (QEI) was analyzed based on mixed linear model for the six target traits. For the flower-related traits, there were 17 pairs of epistasis detected in Q/H population, and many QTLs were found interacted with multi environments significantly. The important genetic regions defined on the chromosome 8 and 10 showed the high level of QEI and the average PVE of interactions were over 15%.Only 3 pairs of epistasis were identified in Y/H population, and the major QTL detected on the chromosome 3 just existed QEI at 1 environment with the 1% PVE of interactions, which was confirmed as an important and stable QTL for the flower-related traits. For the tassel related traits, there were 6 pairs of epistasis detected for TPBN and TW respectively in Q/H population, and the QTL in umc2160-umc1016 interval interacted with 4 environments with the PVE of 21%, while the other more stable QTL identified in bnlg1094-bnlgl579 just showed the low level of QEI (1% PVE) at 1 environment.5 pairs of epistasis for TPBN were found in Y/H population, however there were not any QTLs detected for TW in Y/H under the joint environments.4. There were many consistent genetic regions when compared the results of QTLs detected in this study with other research's reports, i.e. the consistent QTL region in both Q/H and Y/H populations controlling multi flower-related traits on the linkage 3 overlapped with many flower related QTLs detected in different genetic backgrounds with the average PVE of 10%, which indicates 3.04-3.05bin were another important region for flower-related trait besides 8.05bin in Maize. We also identified a major QTL located on 10.04 bin controlling several flower traits in multi environments, which were nearby another reported major QTL for DTP with the PVE of 40%. The stable QTL-Qqtw7-2 for TW found on 7.02-7.03bin closed to ral which regulated the tassel branch length, and the alleles from Huangzaosi increased the TW by 0.55g. The other consistent regions in this study (i.e. QTL for DTT on 2.05bin) were new, which were considered to be detected in the further research.
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