| 21 pairs of combinations were made by testcrossing Q611, a new late-season restorer line which contains two yield-enhancing QTLs yld1.1 and yld2.1 from wild rice and developed by backcrossing the material V20A/O.rufipogon//V20B///V20B////Ce64 (as yield-enhancing QTL donor) to Ce64,a elite late-season rice restorer line as acceptor for three generations and then self-crossing for many generations combining marker-assisted selection (MAS) with field selection in each generation, and restorer line Ce64 to 21 different types of male sterile lines, respectively. The yield-increasing effect of yield-enhancing QTL from wild rice was studied by comparing the yield and yield components of 21 Q611's hybrids to that of 21 Ce64's hybrids (CK) and three elite commercial rice hybrids Weiyou 46 (CK1), Shanyou 63 (CK2), Jinyou 207 (CK3). Furthermore, some morphological and physiological characters were tested with some typical hybrids of Q611 as materials and molecular marker detection and genetic background analysis were conducted on Q611 and its hybrids to probe into the physiological and molecular basis for increasing yield of yld1.1 and yld2.1. The main results are as follows.1) The yield-enhancing QTL from wild rice can increase rice yield remarkably. The average yield of the hybrids of Q611 was remarkably higher than that of the hybrids of Ce64 with 17 of 21 pairs of combinations increasing yield. The rate of yield-increasing combinations was 81%. Among 21 hybrids of Q611, two, seven and eight hybrids have higher yield over CK1, CK2 and CK3, respectively, indicating the yield-enhancing QTLs yldl.l and yld2.1 from wild rice fully expressed in restorer line Q611 and its hybrids.2) Hybrids of Q611 have the characteristics of bigger panicle (the average number of spikeletsper panicle was 244.71, 61.26% more than that of hybrids of Ce64), fewer effective panicles, lower seed-setting rate, lighter 1 000-grain weight and larger sink than that of hybrids of Ce64. They are source-restriction type combinations and seed-setting rate, 1 000-grain weight, grains per panicle and lodging resistance are the main restrictive factors to reach a higher yield. To fully exploit the high-yielding potential of Q611's hybrids, the combinations with high seed-setting rate, heavy 1000-grain weight, many grains per panicle and strong resistance to lodging should be selected.3) The phenotype of hybrids of Q611 was markedly improved compared to that of Ce64's hybrids. They had long and erect functional leaves, small leaf angles, large leaf area and large dry matter accumulation of individuals as well as population and their functional leaves are in good quality with a high and stable weight/area ratio and a high net photosynthesis rate, which prepare sufficient matter for high grain yield. Flowing not smoothly enough is the major restrictive factor to get a higher yield for Q611 's hybrids with both sufficient source and large sink. Keeping flow smoothly are needed to improve seed-setting rate and grain's plumpness for a higher yield of Q611's hybrids.4) Among the high-yielding combinations of Q611, Jinyou 611(Jin 23A/Q611) had a super high yield potential while its plant height was some high and easy to lodge and Weiyou 611(V20A/Q611) had a strong resistance to lodging as well as its male parent Q611. Stronger resistance of base internode to breaking, lower plant height and lighter fresh weight of the plant are helpful to enhancing the resistance to lodging. The correlation between lodging degree in filed and lodging index (LI) of base internode tested in lab was remarkable, indicating LI can be used to evaluate the resistance of lodging when the plants in field are not lodging.5) The results of molecular marker detecting showed tnat the pure yield-enhancing QTLs yldl.l and yld.2.1 from wild rice had been transferred into the DNA of Q611, but the difference of DNA between Q611 and its original parent Ce64 reached to a high level of 38.8%. It was mainly resulted from less backcrossing times, independent selection in the field and linkage inheritance of genes. While selecting the yield-enhancing QTL by MAS method, the selection of morphological characters in the field should be fulfilled independently according to the need of super high yield breeding rather than according to the morphological characters of the acceptor parent, realizing the combining of inner yield-enhancing QTL with outer good morphological characters, which is beneficial to the full expression of the QTL.
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