Developing Near-isogenic Lines And Gene Pyramiding Lines Of Rice Wanjinb Conferring Resistances To Rice Blast By Molecular Marker-assisted Selection

Rice blast is one of the most devastating rice disease caused by ascomycetesMagnaporthe grisea （Hebert） Barr [asexual generation for Pyricularia grisea （cooke）Sacc.].The disease occurs frequently in rice production areas around the world. Excavationand utilization of broad-spectrum lasting resistance genes to rice breeding has beenconsidered as the most economical and effective strategy to control this disease. Pi1, Pi2,Pik-h and Pita-2are dominant and main effect rice blast gene with broad-spectrumresistance. In this study, the rice material C101LAC, C101A51, IRBLkh-K3, IRBLta2-Reand DV8were used as donor parent with resisance gene Pi1, Pi2, Pik-h and Pita-2respectively; and the maintain-line WanjinB was used as resistance gene recurrent receptorparent. By using backcross breeding combined with molecular marker-assisted selectiontechnology, we developed a set of near-isogenic lines and gene polymerized lines with thegenetic background of WanjinB, exploited molecular markers suited to select Pita-2gene，and analysed the agronomic characters of near-isogenic lines. The main results are asfollows:1. Eleven InDel markers near Pita-2gene were developed, in which four InDelmarkers, InDel37, InDel39, InDel43and InDel45, were showed polymorphism betweenWanjinB and DV8. The polymorphic InDel markers with another four SSR markers wereidentified linked to Pita-2gene by F2population derived from WanjinB crossed with DV8.The Pita-2gene was finally mapped between InDel39and RM28033with a geneticdistance of0.4cM respectively. The new identified markers narrowed down the location ofPita-2gene, and it was favourable to marker-assisted selection for the Pita-2gene.2. The individuals harboring Pi1, Pi2, Pik-h and Pita-2gene in backcross andselfcross population were identified by use of markers RM144and RM224for Pi1, AP22and SRM24for Pi2, Pikh for Pik-h, RM28033and InDel39for Pita-2，respectively. Theselected improved individuals with homozygous Pi1, Pi2, Pik-h and Pita-2gene in BC₄F₂population were eight, seven, eleven and nine respectively, and the selected improvedindividuals with Pi1, Pi2, Pik-h and Pita-2gene in BC₅F₁population were eighteen,sixteen, twenty-one and eighteen respectively. A set of near-isogenic lines contained Pi1,Pi2, Pik-h and Pita-2gene with the genetic background of WanjinB were preliminary established.3. The individuals containing Pi1, Pi2, Pik-h and Pita-2gene respectively, andrestoring well to the genetic background of WanjinB were selected from the BC₃F₁population for gene pyramiding. Three lines pyramided Pi1with Pi2and five linespyramided Pik-h with Pita-2were identified in F1generation derived from a cross withdifferent genes individuals; six and twelve homozygous gene pyramiding lines werefurther gained in hybrid F2generation. The pyramiding lines containing Pik-h and Pita-2genes were crossed with the BC4F1lines of Pi2gene, and four pyramiding three geneslines, Pik-h, Pita-2and Pi2, were successfully developed in hybrid F1generation.4. The rates of genetic background of near-isogenic lines with Pi1, Pi2, Pik-h andPita-2recovered to WanjinB were97.3%-98.4%,97.2%-98.3%,97.7%-98.3%and97.6%-98.4%, respectively. The rates of genetic background of pyramiding lines with Pi1and Pi2, Pik-h and Pita-2were both98.4%. There were no significant differencesbetween the near-isogenic lines and their parent WanjinB in major agronomic characterssuch as plant height, panicle length, number of tillers per plant, number of panicles perplant, flag leaf length, flag leaf width, flag leaf aspect ratio, number of spikelets per panicle,number of seeds per panicle, seed setting rate, grain weight per panicle,1000-grain weightexcept days to heading, It was showed that the agronomic characters of the near-isogeniclines had basically restored to that of WanjinB.