QTL Mapping Of Germination Traits With Low-temperature Tolerance In Maize Seeds Based On IBM Syn10 DH Population

Low temperature is a common disaster in maize(Zea mays L.)sowing season in many countries and regions.It has become one of the main climatic limiting factors of maize production and has a great impact on agricultural production.However,the existing maize varieties have poor low-temperature germination ability,so it is an effective way to cultivate new maize varieties with low-temperature tolerance to deal with chilling injury in early spring.Therefore,QTL mapping of low-temperature germination traits in maize can lay a foundation for further fine mapping and map-based cloning,and also provide germplasm resources and molecular markers for maize breeding.In this study,a high-density genetic linkage map was constructed by 6618 SNP markers.208 IBM Syn10 DH lines were used to map the QTL for germination trait with low-temperature tolerance of maize seeds.The results were showed as follows:1.The results of phenotypic identification showed a single peak curve occurred at the frequency distribution of root length,plumule length,seedling length,mesocotyl length,germination index,vigor index,simple vigor index and average germination days of IBM Syn10 DH population at 10 ℃,which basically conformed to normal distribution.The results demonstrated that low-temperature tolerance is a quantitative trait which controlled by polygenes.The maximum value of germination rate,root length,plumule length,seedling length,mesocotyl length was 100%,10.49 cm,5.47 cm,6.33 cm and 1.78 cm respectively,which was increased by30.0%,6.41 cm,4.45 cm,4.89 cm and 1.36 cm compared with B73,the low-temperature tolerant parent line.These low-temperature tolerant lines of IBM Syn10 DH population can be used as germplasms for maize breeding.2.The genotype data of IBM Syn10 DH population were directly obtained from Cy Verse website(http://www.cyverse.org/discovery-environment),and QTL mapping analysis was carried out using the composite interval mapping method.Except for chromosome 10,a total of 25 QTLs closely linked to germination rate,root length,plumule length,seedling length,mesocotyl length,germination index,vigor index,simple vigor index and average germination days were detected on the other 9 chromosomes,with the PVE value of 5.39% ～ 9.49%.3.Further analysis showed that there were 9 overlapping regions among QTL segments of different low-temperature germination traits.In total,2080 candidate genes were mined in these nine overlapping intervals.According to the gene annotation,ten key genes were chosen for q RT-PCR identification.The results showed that there were significant or extremely significant differences in their expression levels between B73 and Mo17(except for gene Zm00001d047039).Among them,the expression level of gene Zm00001d045988(Cytokinin-O-glucosyltransferase 2)in parent B73 was 91.2 times higher than that in Mo17.