| Maize is an important fodder and food crop,and gray spot disease seriously affects maize production in Southwest China.Breeding and planting disease-resistant varieties is the most economical and effective way to control the disease.Among the known maize germplasm resources,there are few materials with high resistance to gray spot disease.Improving the resistance of maize varieties to gray spot disease and creating new corresponding maize germplasm are the key and difficult points of maize breeding in Southwest China.In this study,26 maize elite inbred lines with different heterotic groups were used to identify the resistance to gray spot disease by artificial inoculation.Among them,GD927 with high resistance was selected as the donor parent,and PH4CV(high sensitivity)and 986(susceptibility)were used as recipient parents,to construct four populations A1(GD927/PH4CV),A2(GD927/PH4CV//PH4CV),B1(GD927/986)and B2(GD927/986//986).Using molecular markers,the disease resistance loci of the tested materials were detected and combined with the identification results of artificial inoculation,the main QTL(or gene)linkage markers for resistance to gray spot disease were determined.Using the determined molecular markers,the disease-resistant loci of the isolated generations of the 4 populations were detected,combined with the natural identification in the field,to produce new material for maize resistance to gray spot disease,and to provide technical support for maize disease-resistant breeding.The main findings are as follows:1.Determination of the main QTL linkage markers for maize resistance to gray spot disease: The identification of inoculation against gray leaf spot showed that among 26 maize elite inbred lines,15 materials showed moderate resistance or above,of which 4 were high resistance.Molecular marker detection showed that the disease resistance sites of the tested materials were mainly concentrated in five loci of KHB5(umc2614),q Rgls1.06(umc1972),q Rgls2.04(TID5306),q Rgls2.07(umc1042)and q Rgls3.02(bnlg1523).Among them,KHB5 and q Rgls2.04 are consistent with Qi 319(high resistance,temperate germplasm)disease resistance locus,q Rgls1.06,q Rgls2.07 and q Rgls3.02 and T32(high resistance,tropical germplasm)disease resistance locus point the same.In the tested materials,GD927(high resistance)has both disease resistance loci(KHB5 and q Rgls2.04)consistent with Qi 319,and disease resistance loci(q Rgls1.06,q Rgls2.07 and q Rgls3.02).2.Creation of maize germplasm resistant to gray spot disease: The detection of molecular marker polymorphisms closely linked to the disease resistance loci showed that the SSR molecular markers umc2614,umc1972,umc1042 and bnlg1523 linked to the disease resistance loci of KHB5,q Rgls1.06,q Rgls2.07 and q Rgls3.02 were in GD927 and PH4 CV,There are good polymorphisms between GD927 and 986.Using4 molecular markers with good polymorphism,molecular marker-assisted selection was performed on 363 individual plants in the F2 segregation generation of the A1 population,and 101 individual plants with two or more disease resistance loci were screened.69 individual plants were harvested;356 individual plants of the BC1F1 segregation generation in the A2 population were subjected to molecular markerassisted selection,and 151 individual plants were screened to contain two or more disease-resistant loci.According to the comprehensive field performance,93 individual plants were harvested;Molecular marker-assisted selection was performed on 360 individual plants in the F2 segregation generation of the B1 population,and 87 individual plants with two or more disease resistance loci were screened.According to the comprehensive field performance,44 individual plants were harvested;for the B2 population BC1F1 Molecular marker-assisted selection was performed on 365 individual plants of the isolated generation,and 121 individual plants with two or more disease resistance loci were screened.According to the comprehensive field performance,51 individual plants were harvested.3.Identification of disease resistance of the selected lines: The parents and the selected lines of the A1,A2,B1 and B2 populations were planted in three highincidence areas of gray spot in Guizhou,Yunnan and Sichuan for gray spot resistance identification.As a result,among the 69 lines selected in the A1 population,there were 1 high-resistant material,21 disease-resistant materials,28 medium-resistant materials,18 susceptible materials,and 1 high-susceptible material;93 lines were selected from the A2 population.Among the strains,there are 7 resistant materials,28 moderate resistant materials,55 susceptible materials,and 3 highly susceptible materials;among the 44 lines selected in the B1 population,there are 2 high resistant materials and 15 disease resistant materials,25 medium resistant materials and 2susceptible materials;among the 51 lines selected in the B2 population,there were 11 resistant materials,34 medium resistant materials and 6 susceptible materials.According to the comprehensive field performance,the A1 population obtained 1high-resistance material(A1-50)and 4 resistant materials(A1-28,A1-43,A1-44 and A1-51);the A2 population obtained the disease resistance 5 materials(A2-1,A2-12,A2-15,A2-22 and A2-27);B1 group obtained 2 high resistance materials(B1-23 and B1-36),2 disease resistant materials(B1-1 and B1-10);B2 population obtained 6disease-resistant materials(B2-3,B2-5,B2-21,B2-35,B2-40 and B2-46).From four groups A1,A2,B1 and B2,a total of 20 disease-resistant and above materials were obtained,including 3 high-resistant materials.4.Genetic background analysis of germplasm resistant to gray spot disease:Based on 410 pairs of SSR primers,89 SSR markers with good polymorphism between GD927 and PH4 CV were screened out,and the genetic background of 10 materials obtained from A1 and A2 populations was screened to analyze.As a result,the recovery rates of the 5 materials obtained by the A1 group ranged from 69.66% to71.91%,with an average recovery rate of 70.90%;the background response rates of the 5 materials obtained by the A2 group ranged from 69.10% to 81.46%,with an average background response rate of 70.90%.A1-28,A1-43,A1-50,A2-1,and A2-12 are partial receptor PH4 CV materials,each with 4,3,3,4 and 3 disease resistance sites introduced;A1-44 is a partial receptor The donor GD927 type material has introduced 2 disease resistance sites.Ninety-four SSR markers with good polymorphism between GD927 and 986 were screened out,and the genetic background analysis of 10 materials obtained by screening B1 and B2 populations was carried out.Among them,the recovery rate of genetic backgrounds of 4 materials obtained by the B1 group ranged from 64.36% to 68.09%,and the average background response rate was 65.82%;the background response rates of the 6materials obtained by the B2 group ranged from 70.21% to 74.47%,with an average background response rate of 65.82%.was 72.34%.B1-1,B1-10 and B1-23 are partial donor GD927 type materials,all of which have introduced 2 disease resistance sites;B1-36,B2-40 and B2-46 are partial acceptor 986 type materials,each of which has been introduced 3,4 and 4 resistance loci were identified. |
PDF Full Text Request