The Molecular Marker-Assisted Selection Of Two Sets Of Near Isogenic Lines Of Maize For Disease Resistance

Northern corn leaf blight(NCLB) and head smut in maize,caused by fungi,have been the prevalent diseases in the world,which can cause heavy losses in corn production.Developing disease resistant variety is the most economic and efficient measure to control northern corn leaf blight and head smut in maize.The resistance breeding is based on the deep understanding of genetics of resistance.So far,symptoms,pathogens and epidemics of these diseases have been studied deeply,but studies about mapping and cloning of resistance genes for these diseases are still not comprehensive.In this study, based on the research of predecessors,near-isogenic lines to northern corn leaf blight and head smut of maize are obtained by the way of molecular marker-assisted selection and backcross breeding,which used two inbred lines Mo17(resistant) and Huangzao 4 (susceptible) as parents.The main results are as follows:The molecular marker-assisted selection of resistance near-isogenic lines to NCLB1.Based on 5 major QTLs that were mapped before,305 individuals that had the same genotype as the donor(Mo17) were selected after the foreground selection in the BC₃F₂ population(3000 individuals).2.118 pairs of SSR primers were screened polymorphisms in the 5 QTL locations.The eight polymorphic markers have been found on both sides,including 6 polymorphic markers such as bnlg1327,umc1422,umc1518,bnlg1064,bnlg1138 and umc1736 on chromosome 2 and 2 polymorphic markers,umc1359 and bnlg1863 on chromosome 8. Using these 8 markers selecting in 305 individuals,42 of them have the similar genotype with the donor(Mo 17).3.With 124 polymorphic SSR markers for the background selection of the chosen 42 individuals after foreground selection,42 individuals of 305 individuals have the higher recovery rate,which ranged from 85.4 percent to 95.86 percent.The restoration rates of 13 individuals of them are higher than 89 percent.4.The disease indexes of near-isogenic lines of disease resistance to NCLB in maize lower than the recurrent parent Huangzao 4.It was concluded that the three main-effect QTLs in the chromosome 2 and two QTLs in the chromosome 8 could reduce the disease index.The molecular marker-assisted selection of resistance near-isogenie lines to head smut of maize1.Resistance genes were detected in the 31 individuals of S1 generation using the phi099 linked to resistant QTLs.The result showed that all of them contained the phi099.2.With 55 polymorphic SSR markers for the background selection of the chosen 31 individuals of S1 generation,31 individuals have the higher recovery rate,90.4 percent in maximum and 71.8 percent in minimum.The average restoration rate of 31 individuals are 80.5 percent,the three of them are higher than 85 percent percent.They were HS195-1 for 85.4 percent,HS195-20 for 90.4 percent and HS140-4 for 87.2 percent.