| Rice is one of the most important crops in the world and plays an important role in ensuring food safety. However, water shortages have become the main limiting factor of crop production in many countries, which also have a great influence on the development of rice production. Practice shows that crop yield is the final indexes of drought resistance evaluation and that the effective way to reduce limited-effect of drought stress is breeding drought-resistant rice varieties, which is one of the main goals of rice breeding. Excavation the drought tolerance-related QTLs and their closely linked molecular markers through the QTL mapping using molecular marker technology, and regulation drought tolerance at molecular level are effective ways to improve the drought tolerance of rice varieties.In this study, Xiaobaijingzi (an upland rice variety) and Kongyu131(a widely cultivated rice variety) were used as female and male parent, respectively. The two parents and the population derived from the parents, which consisted of220F6:7and F6:8recombinant inbred lines (RILs), were used as experimental materials. In2012, the materials were grown at Northeast Agricultural University’s experimental base (El) and Tieli experimental base (E2). And in2013, they were grown at Northeast Agricultural University’s experimental base (E3), Acheng experimental base (E4) and Tieli experimental base (E5). All of the experimental bases were located in Heilongjiang province. The experiments were laid out as a factorial design with fully irrigated and drought-stressed treatments (two replicates of each) at each place. With SSR molecular markers and the investigation of the traits, such as plant height (PH), number of panicles per plant (PN), panicle length (PL), primary branch number (PBN), secondary branch number (SBN), number of grains per panicle (GN), seed setting rate (SSR) and yield per plant (YP), the effects of QTL additive, epistasis and QE interaction were studied and the yield QTL by conditional and unconditional were detected. The main results were as follows:1. The PH, PN, PL, PBN, SBN, GN, SSR and YP of parents and populations decreased obviously under drought stress in each place. The PH, PL, PBN, SBN, GN, SSR of Xiaobaijingzi decreased less than those of Kongyu131and the damages were relatively mild, but the some performance is different under different places, the PN and YP had no significant difference.2. Genetic linkage maps were constructed using MapMaker/EXP3.0and Mapchart2.2mapping software, and the RIL consisted of220as the mapping populations. The maps contained104SSR markers; the markers were loeated on11chromosomes except chromosomes10. The full-length of the map is1295.03cM, and the average distance is12.45cM Marker numbers on each chromosome were5 to17.3. According to the expression of the main-effect QTLs for the traits under the different conditions, three categories were found:The first one was detected only in the control condition, the second one only in the drought-stress condition, and the third one in both conditions. In addition, the difference across the two conditions was also detected, the results were as follows:4.19QTLs belong to the Type Ⅰ were detected that included4PH QTLs,4PN QTLs,4PL QTLs,4PBN QTLs,4SBN QTLs,2GN QTLs and1YP QTL.5.17QTLs belong to the Type Ⅱ were detected that included4PH QTLs,2PN QTLs,2PL QTLs,1PBN QTLs,3SBN QTLs,3GN QTLs,1SSR QTL and1YP QTL.6.11QTLs belong to the Type Ⅲ were detected that included1PH QTL,2PN QTLs,2PL QTLs,1PBN QTL,3GN QTLs and2YP QTLs.7.6QTLs affecting trait differences between stress and control were identified that included3PH difference QTLs,1difference PN QTL,1PL difference QTL and1GN difference QTL.8.21QE QTLs were detected respectively qPH-4-1, qPH-7-2, qPN-7, qPL-4, qPL-7,qPL-2-1, qPL-2-2, qPL-3, qPBN-7, qSBN-1-2, qSBN-7-2, qSBN-1-3, qSBN-4-1, qSBN-7-1, qGN-1-2, qGN-1-4,qGN-7-2, qGN-1-5, qGN-7-1,qYP-7-2and qYP-7-3.9.22pairs of epistatic QTL were detected and contained6pairs of epistatic QTL on PH,2pairs of epistatic QTL on PN,3pairs of epistatic QTL on PL,1pairs of epistatic QTL on PBN,2pairs of epistatic QTL on SBN,4pairs of epistatic QTL on GN,1pair of epistatic QTLon SSR and3pairs of epistatic QTL on YP.10.9pairs of epistatic QTL showed QTL×environment interactions, contained1pair of epistatic QTL on PH(qPH-1-1and qPH-3-3),2pairs of epistatic QTL on PL(qPL-2-1and qPL-6-2, qPL-5-1and qPL-6-2),1pair of epistatic QTL on PBN(qPBN-4and qPBN-6),2pairs of epistatic QTLon SBN(qSBN-5-1and qSBN-6-1,qSBN-5-2and qSBN-6-2),1pair of epistatic QTL on GN (qGN-1-2and qGN-4),2pairs of epistatic QTLon YP (qYP-8and qYP-9,qYP-6-1and qYP-7-1).11. Conditional QTL mapping and epistatic QTL were conducted for yield when PH, PN, PL, PBN, SBN, GN, SSR were predetermined.When PH, PN, PL, SBN, GN, SSR were predetermined,1QTL was detected, respectively. When PBN was predetermined,2QTLs were detected. When PL, GN, SSR were predetermined,1pair of epistatic QTL were detected, respectively under control conditions. When PH PL, PBN, SBN, GN, SSR were predetermined,1QTL was detected, respectively. When PN was predetermined,3QTL were detected. When SBN, GN, SSR were predetermined,1pair of epistatic QTLs were detected, respectively under drought stress.This research has detected the same interval of the QTLs as previous report, which indicated that these QTLs could stable expression in different environment and has good application value in the marker-assisted selection of drought-resistance rice. The yield QTL under drought stress and normal water conditions are less detected by conditional and unconditional methods, thus those yield QTLs related to drought resistance were detected in this study play some role in the Molecular assisted breeding of drought-resistance rice and offer some informations for future research. |
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