Fine Mapping And Mining Of QTL Genes For Lodging Resistance Traits In Maize

Maize（Zea Mays L.）is one of the most important crops,not only as a food crop and quality feed,but also as an important industrial raw material.Lodging is a complex character caused by gene,environment and cultivation conditions.It is a quantitative character with complex genetic mechanism.Although some studies have located QTL related to maize stalk strength and obtained many molecular markers related to corn stalk strength,the regulation mechanism of maize stalk strength is still unclear.A large number of QTLs and genes related to maize stalk strength have not been effectively excavated.Therefore,it is of great significance to explore the regulation mechanism of stem strength and develop molecular markers related to lodging resistance for the improvement of lodging resistance traits in maize.In this study,3705I（lodging inbred line）and LH277（lodging resistant inbred line）were used for constructing mapping populations.The rind penetrometer resistance was selected as indicators for QTL mapping.Candidate genes related to lodging resistance traits were mined.At the same time,molecular markers related to lodging resistance traits were developed.The main results are as follows:1.The phenotype of 10 maize inbred lines related to lodging were observed for many years,among which 3705I（lodging inbred line）and LH277（lodging resistant inbred line）were screened.It was found that the RPR of all stems under the primary ear of 3705I and LH277increased rapidly before tassel stage.Moreover,the growth rate of LH277 RPR was higher than that of 3705I.After tassel stage,the RPR of all stems under the primary ear of 3705I and LH277increased slowly or basically did not increase.2.By lignin staining and content measurement of cell wall component,it was found that there was no significant difference in cellulose and hemicellulose content between the two inbred lines 3705I and LH277,while lignin content in LH277 was significantly higher than that in 3705I.3.By using scanning electron microscopy,it was found that LH277 had thicker rind sclerenchyma,rind sclerenchyma cell wall thickness,vascular sheath thickness and vascular sheath cell wall thickness than 3705I,and the thickened secondary wall made the entire cell lumen almost disappear.4.3705I（lodging inbred line）and LH277（lodging resistant inbred line）were used for constructing F₂ and F_2:3 populations.14 QTLs were detected and explained 4.14-15.89%of RPR phenotypic variation.qRPR1-3 and qRPR3-1 accounted for more than 10%of phenotypic variation and were detected in multiple environments.So both of them were used as the dominant QTLs for further fine mapping.5.Based on the resequencing results of 3705I and LH277,we developed 12 In Del and 1CAPS polymorphic molecular markers within the initial mapping interval of QTL qRPR1-3,and 9 In Del and 1 CAPS polymorphic molecular markers in QTL qRPR3-1 for further fine mapping.6.Through the continuous fine mapping of BC₅F₁,BC₇F₁ and BC₉F₁,qRPR1-3 was narrowed from the initial 26 Mb interval to a physical distance of 906 kb between mmc0041and 3L1-244.1.Based on the reference genome B73 AGPv4,14 candidate genes were identified in 4 Mb region.7.Through the continuous fine mapping of BC₅F₁,BC₇F₁ and BC₉F₁,qRPR3-1 was narrowed from the initial 4.5 Mb interval to a physical distance of 550 kb between Snp3 and1027.Based on the reference genome B73 AGPv4,12 candidate genes were identified in 550kb region.8.According to the expression pattern and nucleotide sequence difference of 12 candidate genes.Zm00001d039637 may be the candidate genes that caused the difference of stem RPR.