| Founder parents have played very important role in crop breeding and production in China, but there were few studies on founder parents about the formation and genetic basis, which lead to difficulty to predict and make full use of them. So, it will be very helpful to exploring the formation mechanism of founder parent comprehensively and reach higher aims of super high yield and high efficient breeding in wheat to analyze the inherited characters of founder parent about the stripe rust resistance, endosperm storage protein and composition of important chromosomes.In this study, Bima 4's 80 progenies which fall into different generations, 18 intermediate parents related to this pedigree, 6 sister cultivars (from Bima 1 to Bima 6) and their parents (total 106 accessions) were analyzed. Firstly, seventy-seven accessions were appraised using 23 different stripe rust races at seedling stage in greenhouse and resistant genes were postulated, at the same time, their reactions to powdery mildew and stripe rust in field were tested; secondly, the endosperm storage protein composition of total accessions were evaluated; finally, 98 accessions were analyzed using 48, 26 and 25 SSR markers on the chromosomes 2A, 1B and 1D which carried many important genes loci such as Yr1, Yr9, Glu-1, Gli-1 and Gli-2 respectively, and association test among the SSR markers and agronomic traits including spike length, spikelet number, grain number, 1000-grain weight, spike number per plant, plant height and yield from 5 different ecological areas were done. The major results were as follows:1. Reactions to different stripe rust races and the genes postulated in derived pedigree of Bima 4(1) Five stripe rust resistant genes were postulated in 77 accessions. Eighteen (25.7%) of tested accessions carry the stripe rust resistant gene Yr1, nine accessions carry the gene Yr9, such as Fengkang 1, and the genes Yr2, Yr25 and YrHVII were postulated in Jimai 23.(2) Bima 4 had Yr1, and so do 4 (30.8%) of 13 accessions in the first generation and 11 (36.7%) of 30 tested accessions in the second generation. What'more, Yr1 did not be discovered in 3 and 11 intermediate parents of the first and the second generation respectively. In addition, only 1 (Youmanghong 7) of 4 tested accessions in the third generation had Yr1, and the remaining accessions (75%) had Yr9; only 1 (Jing 411) of 8 tested accessions in the fourth generation had Yr1, and other 4 accessions (50%) from Lovrin 10 had Yr9. This indicated that the gene Yr1 in the first and second generations had undergone selection to some extent, whereas Yr1 could also be found in some accessions in the third and fourth generations despite of the appearance of Yr9 with high proportions.(3) When compared the infection types to different stripe rust races among Bima 4 and its progenies, the resistance of Bima 4 were prefer to transmit. To 13 stripe rust races which Bima 4 presented resistant, 36 to 49 accessions of Bima 4'progenies were likewise, however, to other 10 stripe rust races which Bima 4 was susceptible, 7 to 28 accessions of Bima 4'progenies showed susceptible.(4) When compared the infection types to different stripe rust races among various sister cultivars derived from the same cross in the pedigree derived from Bima 4 and selected cultivars from Beijing 14, they presented very different. Inconsistent phenomenon existed between sister cultivars and their parents, so do selected cultivars and Beijing 14. 2. Glutenin and gliadin composition of tested accessions(1) HMW-GS composition: the HMW-GS of Bima 4 at Glu-1 were null, 7+8 and 2+12, respectively. At Glu-B1 locus, there were different alleles among Bima 4 and other three parents in the first generation, and the frequency of 7+8 subunit of Bima 4 was up to 84.6% in this generation. Six (54.5%) intermediate parents in the second generation had the same subunit 7+8 as Bima 4, and this subunit could be found in 64.1% of total accessions in this generation. But only two of five parents in the third and fourth generations had 7+8 subunit, its frequencies were rather low, and 7+9 became dominant with the frequencies of 69.2% and 64.3%, respectively. At Glu-A1 and Glu-D1 loci, 11 (64.7%) of all intermediate parents had the same subunits (null and 2+12) as Bima 4, respectively, and their frequencies were over 76.9% in each generation.(2) Gliadin composition: Bima 4 had 16 gliadin bands, and Gli64.5 was different from all other parents, which was inherited to 11.3% in progenies. Eight bands (Gli16.7, Gli18.9, Gli47.7, Gli56.7, Gli62.2, Gli66.9, Gli74.3 and Gli81.7) detected in Bima 4 kept high frequencies in four different generations, ranging from 59.0% to 100%, and they could be also found in most of the parents in this pedigree, whereas gliadin bands (Gli20.9, Gli28.1, Gli30.0, Gli33.0 and Gli52.3) had high frequency in one or several of the various generations.3. SSR analysis(1) When analyzing the inheritance of alleles of Bima 4 in each progeny, the result indicated that there were various chromosomal regions. What'more, the length of chromosomal regions varied among different accessions and different generations, indicating that there might be diverse contribution about found chromosomal regions, and the selection in the breeding programs for different objects exerted certain influence on them. The progenies of Bima 4 were distributed in two agro-ecological zones, namely Huang-huai Valley Winter Wheat Areas (33 cultivars) and Winter Wheat Region in North China (47 cultivars). At Xgwm515 and Xgwm249 loci on the chromosome 2A, Xgwm124 locus on the chromosome 1B and Xcfd65 and Xcfd282 loci on the chromosome 1D, these accessions in Winter Wheat Region in North China had the same alleles as Bima 4, which might be much more important for the cultivar formation in this region.(2) Association test indicated that 31 (39.2%) of tested markers were associated with agronomic traits (including spike length, spikelet number, grain number, 1000-grain weight, spike number per plant, yield and plant height). Further, the alleles of Bima 4 showed different (positive or negative) effects between different loci or different traits, which might be due to the interaction among them.4. Comparison between Bima 1 and Bima 4Bima 1 and Bima 4 presented resistance to 16 and 13 different strip rust races at seedling stage, respectively, and both of them carried Yr1. Compared with Bima 1, Bima 4 had 8 unique gliadin bands, among them Gli74.3 and Gli81.7 had high transmission frequencies in the various generations derived from Bima 4, and Gli20.9 were selected to some extent. Bima 4 and Bima 1 had the same composition of glutenin.Founder parent Bima 4 and large-area-planted cultivars Bima 1 had the same composition at Yr1 and Glu-B1 loci, but the further SSR analysis indicated that differences exist in nearby chromosomal regions of this 2 loci between the two cultivars. Association test discovered chromosomal segments with high transmission frequencies associated with important traits in related chromosome regions. Distal short arm of 1D and 6D contained Gli-1 and Gli-2 loci also had chromosomal segments with high transmission frequencies associated with important traits. There were 1 locus which could be transmitted to the fourth generation in distal short arm of 6AS and 6BS. Unique gliadin of Bima 4 with high frequencies in progenies probably related with these chromosomal segments or loci.On the basis of analysis above, the resistant gene to strip rust detected in Bima 4 was very important factor as founder parent. On the other hand, the endosperm storage protein encoding gene loci Glu-B1, Gli-1 and Gli-2 were also selected when other important traits such as resistance to strip rust were chosen. The SSR analysis and association test indicated that Bima 4 had chromosomal segments with high transmission frequencies associated with important traits in related chromosome regions. These chromosomal segments probably were the important characters of founder parent Bima 4. |
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