| Rice blast caused by Pyricularia grisea and rice bacterial blight caused by Xanthomonas oryzae pv. oryzae (Xoo) were two kinds of the most serious rice diseases and mainly limited factors to rice yield stability. With a population of blast pathogen derived from central and southern China, a F9-10 rice recombinant inbred line (RIL) population developed from cross ZS97XMH63, and a barley doubled haploid (DH) population generated from cross Harrington xTR306 (from the North America Barley Mapping Project), the goals of the study were to obtain structure and frequency of pathotype of blast pathogen population in central and southern China, and to gain comparative mapping of blast-resistance-related QTL between rice and barley, moreover, comparative mapping of resistance-related QTL between blast and bacterial blight using the same map population.The main results were as follows:1. Analyses on population structure of P. grisea in central and southern ChinaUp to 792 isolates which were chosen from a primary population with 1,923 isolates were inoculated onto 13 differentials which belonged to two sets of near-isogenic lines (NILs), including 6 indica NILs and 7 japonica NILs. The results indicated that the given population was very complex. Based on indica or japonica NILs, 48 or 82 pathotypes were identified, respectively. Considering the two sets of NILs, as many as 344 pathotypes could be distinguished. Pathotype distribution relied geographically on different rice grown areas or provinces. Alternatively, reaction type and its frequency of every NIL were quite different, i.e. isolates differed in sensibility to blast-resistance genes. Major resistant genes had different resistance spectra, and Pi2 and Pil possessed the widest resistance spectra to pathogen isolates.2. Comparative mapping of disease resistance QTL of rice and barleyIn rice, 8 blast-resistance QTL were detected on 4 of 12 chromosomes using interval mapping method, while 17 QTL were detected on 8 of 12 chromosomes using mixed linear model-based composite interval mapping method. With two mapping method, the biggest LOD value QTL is located on chromosome 2, between marker RM213 and RM208, with Max LOD value, 32.30 and 52.01, and their contribution to variance, 51.7% and 55.20%, respectively. It was a major QTL, and it offered resistance to three detected P. grisea isolates. In barley, 8 and 9 blast-resistance QTL were identified using above two mapping methods, respectively. Among them, there were 5 QTL were mapped on the same chromosome location, and 3 on the nearly location. With two mapping methods, the largest QTL was located around MWG914 on barley chromosome 7 (5H), which couldexplain variance of 31.4% and 22.99%, respectively.Homoeologue were detected in 4 pairs including 7 QTL between rice and barley They were involved in homoeologue of chromosome fragments in rice and barley as followed: Homoeologue between 2 QTL, qld9 and q119, located on center and near-terminal of long arm of rice chromosome 9 and 1 QTL, qld5Ha, located within ABC717-MWG914 at the center of long arm of barley chromosome 7(5H); Homoeologue between QTL - qld8 on rice chromosome 8, qln3 - on rice chromosome 3 and two QTL at the center of long arm and near marker CDO504 of barley chromosome 5H - qld5Hb, qln5H, respectively.With interval mapping method, 15 rice bacterial blight- resistance QTL were probed to locate on 8 of 12 rice chromosomes. Among them, three major QTL were located at interval Y6854L-RM224, Y2668LA-L1044 on chromosome 11, and R887-G1314b on chromosome 12. With mixed linear model-based composite interval mapping method, 3 major QTL still were detected. Of them, one located on chromosome 12 to strain PXO339 aligned with location deduced from interval mapping method, one situated around marker RM224 on chromosome 11 to strain JL691 closely linked to location calculated from interval mapping method, and one mapped to Y6855RA-R543a to strain PXO61. At the same time, five minor relative bacterial blight- resistance QTL were distinguished in...
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