| Rice blast, caused by Pyricularia grisea (synonymous Pyricularia oryzae Cav.; teleomorph Magnaporthe grisea), is considered the most important disease of rice because of its worldwide distribution and the resulting severe yield loss. Although a great number of genes for complete and partial resistance to rice blast have been mapped with DNA markers, few work dealt with neck blast, especially on mapping quantitative trait locus (QTL) for neck blast. Progresses on molecular mechanisms of interactions between rice plants and M. grisea have been obtained in recent years as well.In our previous work, an RIL population consisting of 304 lines was constructed from the indica cross Zhong 156/Gumei 2. Two genes conferring complete resistance to blast isolate 92-183 (ZC15) were primarily mapped by using 148 lines of the population. In the present study, genotype of the 304 RILs were analyzed and QTL mapping for partial resistance to 2 isolates of leaf blast and 1 isolate of neck blast were conducted. A pair of near isogenic lines (NILs), which possessed similar genetic background but different alleles on the locus resistant to both leaf blast and neck blast, was used for mRNA differential display and cDNA microarray. The main results were as following:1. A linkage map with 168 DNA markers including RFLP, SSLP, RAPD, RGA and CG covering all 12 chromosomes basically and spanned for 1447.9 cM was constructed by using the total RIL population. Linkage relationships between DNA markers and the two resistance genes conferring complete resistance to isolate 92-183 were re-analyzed. One major gene only resistant to leaf blast, Pi-24 (t) was co-segregated with an RAPD marker N7 and no recombinant was found on the locus in all of the susceptible lines. The other major gene resistant to both leaf blast and neck blast, Pi-25 (t) was flanked by one RFLP marker RG456 and one RAPD marker A7, the distances between the gene to the two markers were1.5cM and 1.8cM respectively.2. QTL mapping for partial resistance to blast were conducted by using the total population. A total of 62 QTL scattered on 28 intervals of the 12 chromosomes were detected for parameters of partial resistance to leaf blast to two isolates and neck blast to one isolate. The parameters included Diseased leaf area (DLA), Lesion size (LS), Lesion number (LN), Lesion length (LL) and Condium amount (CA). The number of QTL detected ranged from 1 to 6 for each interval. The average was 2.2 QTL per interval. During the infection of isolate 99-30-1, a total of 7 QTL were detected for DLA. Among them, 1 QTL showing main effectIXonly and 6 QTL showing epistatic effect only, they could explain 5.9% and 50.8% of total phenotypic variation respectively. A total of 3 QTL were detected for LS. Among them, 1 QTL showing main effect only and 2 QTL showing epistatic effect only, they could explain 9.1% and 16.4% of total phenotypic variation respectively. A total of 10 QTL were detected for LN. Among them, 2 QTL showing main effect only, 7 QTL showing epistatic effect only and one QTL showing not only main effect but also epistatic effect. The main effect and epistatic effect could explain 25.4% and 38.1% of total phenotypic variation respectively. During the infection of isolate Ca89, a total of 8 QTL were detected for DLA. Among them, 1 QTL showing main effect only and 7 QTL showing epistatic effect only, they could explain 5.0% and 34.8% of total phenotypic variation respectively. A total of 8 QTL were detected for LS. Among them, 1 QTL showing main effect only and 7 QTL showing epistatic effect only, they could explain 6.8% and 38.5% of total phenotypic variation respectively. A total of 5 QTL were detected for LN. Among them, 1 QTL showing main effect only, 3 QTL showing epistatic effect only and one QTL showing both main effect and epistatic effect. The main effect and epistatic effect could explain 9.6% and 16.1% of total phenotypic variation respectively. During the infection of isolate 92-183, for CA, one parameter of partial resistance to neck blast, a tot...
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