| Backbone parents have played an important role for the development of wheat in China, which have produced many large-grown varieties and important breeding lines. Analyzing the agronomic traits and the genetic structure characteristics of backbone parents has great significance in studying and utilizing them better, as well as creating new milestone parents and selecting parents in cross breeding. With wheat milestone parent Bima 4 and its progenies, this study tried to reveal the main agronomic traits, the specific genome loci and their transmission in derivatives of Bima 4 by field investigation and genomic scanning. Main results were as follows:(1) Eighty wheat varieties were planted in the agronomy experiment station of Shandong Agricultural University from October 2006 to June 2009, and main agronomic traits were surveyed and analyzed. The results indicated that the milestone parent Bima 4 was more atrractive than other three parents of the first generation verieties, i.e., Early Piemium, Jubileina 2, and Ckopocneлka JI-1 on spikelets per ear, grains per ear, 1000-grain weight, and yield per plant. Furthermore, Bima 4 produced prominent contribution to its progenies in primary yield factors of wheat such as grain number per ear, 1000-grain weight, yield per plant and so on.(2) The four parents of the first generation varieties of Bima 4 were genotyped using 193 EST-SSR markers that were not localized to certain chromosome. As a result, 6 Bima 4 pecific markers were detected, and 41 alleles could be amplified using them. In addition, the 6 EST-SSR markers were localized to certain chromosomes using Chinese spring nulli-tetrasomic lines of wheat. Markers ww106, ww114 and ww122 were assigned to chromosome 1A, markers ww123 and ww176 were assigned to chromosome 2D and 3B respectively; and ww84 was localized to chromosomes 6A, 7A and 6D.(3) The four parents of the first progenies of Bima 4 were analyzed by a total of 1432 SSR, EST-SSR and STS markers (including 193 EST-SSR markers aforementioned) covering the whole genome of wheat. Thirty-nine markers were effective to trace specific loci of Bima 4 from the first to the fourth generation. In the first and the second generations, 38 markers, except for Xgwm577, could amplify the specific bands of Bima 4. In the third and the fourth generations, 35 and 25 specific markers were observed, 10 and 6 loci had the transmission rate over 50.0%, respectively. Among the specific loci, ww122, Xgwm261, Xedm80, SWES222 and CFE223 possessed the inheritable frequency over 50% in all four generations. Besides, 22 specific loci of Bima 4 were detected in the progenies with genetic contribution ratio over 25%. So it was speculated that these important loci and the nearby chromosome regions of Bima 4 should be intensively selected in breeding programs.(4) There were 22 Bima 4 specific loci with genetic contribution ratio over 25% to its derivatives. Nine out of the 22 Bima 4 specific loci were detected by EST-SSR markers. According to wheat genetic maps reported and genes and QTL identified, we found that 8 out of another 13 SSR markers were related to some important agricultural traits. For instance, BARC83 was associated with QTgw.ucw-1A, QGlui.ucw-1A, QSev.ucw-1A and so on; BARC13 was associated with QYr.sgi-2B.1, QEet.inra-2B and so on; Xgwm261 was associated with QGy.ccsu-2D, QHi.ccsu-2D.2, QSl.ccsu-2D.2 and so on. These results indicated that some desirable traits such as yield, grain quality, disease resistance and adaptability may be connected with these chromosomal loci and regions of Bima 4. This could be the basic genetic features of Bima 4 acting as a milestone parent. |
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