Comparison On Different Methods For Measuring Root Traits And QTL Analysis On Root Traits In Wheat

In order to find a more practical and easier approach for measuring root traits, the parentsand F4lines from two separation populations of wheat were used as materials, Cigar culturingmethod, Pipe culturing method and soil-drilling method were used to measure the root traitsin this study. By comparative analysis of the root traits measured by different methods, we arelooking for convenient and energy saving method to measure root traits. The relationshipbetween root traits with photosynthetic traits and agronomic traits was also studied so as tounderstand the effects of root traits on agronomic traits and explore the reasonablecomposition of roots. For locating QTLs related to root traits, SSR marker was used toconstruct genetic linkage map in order to promote the research of wheat root traits and its usein genetic improvement. The main results were as follows:(1) Analysis of relationship among root dry weight, it showed a positive correlationamong Cigar culturing method, Pipe culturing method and soil-drilling method used in thisstudy. Root dry weight from Soil-drilling method was significantly correlated with that ofPipe culturing method. A significant correlation was also observed among that from the threemethods in SD population.(2) The relationship between root dry weight and photosynthetic traits was analyzed andshowed that all root traits were weakly associated with photosynthetic rate and transpirationrate, but not associated with stomatal conductance and Ci. Further analysis found that the rootdry weight from these three methods was positively correlated with grain yield, biomass,grain number per spike and1000-grain weight. The root dry weight from Cigar culturingmethod had a observable positive correlation with grain yield, plant hight, number of effectivetillers, grain number per spike and1000-grain weight, but that from Pipe culturing methodwere weakly associated with most of the agronomic traits.(3) Lines with higher root dry weight was significantly higher in yield, biomass, plantheight, number of effective tillers, spike length, grain number per spike and1000-grain weight than lines with lower root dry weight, but there was no significant difference inphysiological traits between them, except photosynthetic rate. The increase of seedling rootdry weight was mainly due to the increase of root length. The difference in root dry weight atmature stage was mostly caused by the roots that existed in the superficial layer of soil. Theroot dry weight in different depth layers resulted a positive correlation with grain yield.Though the root dry weight in deep layer contributed a small part to the total dry weight (5%),it also showed a positive correlation with yield.(4) The wheat population used in this study had larger scope of phenotypic variations inroot dry weight, total root length, which was suitable for QTL mapping. A primary geneticlinkage map was structured which composed of126SSR markers, which covered20pairs ofchromosomes of wheat. The length of the genetic linkage map is1205and1284cM, withaverage distance between markers of30and22cM, respectively. Eighteen QTLs weredetected for root traits, including5QTLs located on4A chromosome which related to rootdry weight measured by Pipe culturing method,7QTLs located on4D chromosome whichrelated to root-shoot ratio measured by Pipe culturing method,6QTLs located on6Achromosome which related to root dry weight measured by Cigar culturing method.