Identification Of QTL For Seedling Root Traits Using RIL Population In Maize

Root systems of corn serve many functions among which anchorage of the plant and uptake of water and nutrients are the most important ones. Improvement for root traits could lead to important benefits for increasing and stabilizing yield, particularly under drought conditions. Maize plays a very important role not only for the cereal crop over the world, but also for the basical biological study. Recently, the rapid development of molecular markers technology provides a great opportunity to study the genetic factors underpinning the variation of quantitative traits. In this study, a RIL population derived from an elite maize hybrid (Yuyu22) was used as materials, which were grown under the sand culture. Trait data of their roots in seedling after 4, 9, and 14 days of germination was evaluated with WinRHIZO, an optical-scanner-based image analysis system. With the genetic map by SSR markers, QTL associated with roots were mapped in order to explore the genetic basis of maize roots.The major results are as follows.1. A genetic linkage map containing 259 SSR polymorphic markers was constructed, which spanned a total of 2658.6cM with an average interval of 10.26cM. Compared with other published maize linkage maps, marker alignments and intervals were in agreed with them.2. Total lengths, surface areas, root volumes and numbers of lateral roots, number of root tips, average diameter were evaluated. The data revealed that the growing of traits except average diameter had obvious dynamic characters. And the means of two parents were lower than the RIL population except average diameter in three times and volume after days 4 of germination. As a result, the population showed over-parent segregation.3. QTL affecting developmental behavior of root were mapped based on the combining analysis of composite interval mapping mapping method. Totally 27 QTL affecting root were detected on eight different chromosomes. The contributions to phenotypic variations for the single QTL varied from 5.5% to24.5%.The results revealed that genes controlling root had obvious dynamic characters.4. Based on the bin framework of the UMC reference map, the presently available on QTL for root traits in maize including our study were compared. Many QTL had the same or similar bin locations in experimental materials with different genetic background. For example, RV1-1 (binl.06), RN2-1 (bin2.03), R110-1 (binl0.04).5. Based on molecular marker linkage maps of rice and maize, the syntenic relationships of QTL were compared for root traits between maize and rice. Many QTL controlling same or similar traits in maize and rice had corresponding locations and conserved specificity, which suggested a common origin and conserved functionality of the genes underlying the QTL.