Construction Of Genetic Linkage Map And Identification Of QTLs For Important Agronomic Traits In Introgression Lines Maize

Maize(Zea mays L.)is an important food and energy crop which plays a positive role in globel ecnomic development.The parameters such as height,ear height and characteristic of spikes and the relationships among them controlled by minorgene are important for corn yield per unit.To understand the genetic mechanism of traits correlatived with yield,we conducted the research on genetic basis of corn yield traits by molecular approch in different environment treatments.The research objective of this study was to improve the traits of maize introgession line PHB1 M on its plant height and ear length.An introgression line was constructed by adonor line of Four-287,which provides new material for maize breeding.a high-density molecular map of maize was constructed,and the phenotype of 7 agronomic traits including plant height,ear lengthand leaf number were identified,and QTL mappinganalysis was performed,which provides a theoretical and technical support for genetic improvement of maize varieties and development of candidate genes.The main results were as follows:1 In this study,seventy SSR and 64 SRAP primer pairs were screened.The parents and 208 introgression lines of maize were tested by PCR using the obtained primers.In total,793 polymorphic sites were identified including 197 SSR and 576 SRAP markers.By linkage analysis of the polymorphic sites using JoinMap(ver.4.0),a molecular genetic map a length of 1917.2 cM,comprising 10 linkage groups and 644 markers,was constructed.And 133 SSR and 511 SRAP markers were identified with an average interval of 2.98 cM between two adjacent markers.2 Seven traits in relation to yield,including plant height,ear position,leaf number,ear length,ear diameter,ear row number and hundred-grain weight,were analyzed with SPSS 18.0 under 4 different environmental conditions for 208 individual plants in populations of maize introgression lines.The results show that differences in 7 traits all conformed to a normal distribution and belonged to typical quantitative traits which contributes to QTLs.A QTL map was constructed with the above 7 agronomic traits under 4 environmental conditions through multiple QTL models by using MapQTL 4.0 at LOD >3.A total of 193 QTLs which mainly distributed in 9 of 10 linkage groups were detected.46 QTLs were related to plant height,34 were related to ear position,32 were related to leaf number,17 were related to ear length,25 were related to ear diameter,23 were related to ear row number and 16 were related to hundred-grain weight,respectively,which provides a reference for QTL fine mapping and gene clone for plant architecture and ear traits in maize.3 Among of the 193 detected QTLs,20 were consistently expressed under 2 conditions including 5 QTLs for controlling plant height,1 QTL for ear position,2 QTLs for leaf number,3 QTLs for ear length,5 QTLs for ear diameter and 4 QTLs for ear row number.Plant height and ear height were detected as target traits.The results show 6 QTLs(qPH1-6-5 and qPH2-6-6,qPH1-6-6 and qPH2-6-7,qPH2-4-5 and qPH4-4-3,qPH3-7-6 and qPH4-7-11,qPH1-7-11 and qPH3-7-8,qEP1-4-2 and qEP2-4-1)consistently expressed,which provides a foundation for further research on molecular improvement and fine mapping.4 On 6 linkage groups,QTLs were distributed in clusters among 42 markers,including 5 QTLs on the 3rd linkage group,7 on the 4th linkage group,2 on the 5th linkage group,3 on the 6th linkage group,20 on the 7th linkage group,and 5 on the 8th linkage group,which might be able to serve as the screening of candidate genes.