QTL Identification Of Nitrogen Uptake, Plant Height, Grain Yield And Seedling Root Traits In Wheat (Triticum Aestivum L.)

QTL identification of nitrogen uptake, plant height, grain yield and root traits of wheat ishelpful for molecular marker assistance and Pyramiding breeding for high nitrogen useefficency and heigh yield. In this study,202DH (double haploid) lines and parents Avalon×Cadenza were studied. Windows QTL Cartographer2.5and QTLNetwork2.0were used todetect QTL (quantitative trait locus or loci), additive QTL×environment interaction andepistasis QTL×environment interaction for nitrogen uptake (2010and2011, heigh nitrogentreatment), grain yield (2010and2011, heigh nitrogen treatment) and plant height (2008and2009, low nitrogen treatment;2010and2011, heigh nitrogen treatment) in the field, WindowsQTL Cartographer2.5was used to detect QTL for seedling root traits which were cultured inpapper roll system. The relationships between seedling root traits and nitrogen uptake, plantheight and grain yield were analyzed. Moreover, in this study, Rht NILs (near iso-genic lines)and Watkins collection wheat were cultured in papper roll system to find the geneticrelationship between seedling root and plant height (in the field). The results would be veryhelpful to high nitrogen use efficiency and high yield breeding. The results as follows:1. Nitrogen uptake QTLNine QTL for nitrogen uptake (in2010and2011and mean value of two years) weredectected by Windows QTL Cartographer2.5. Among them,2QTL on chromosome2D and4B were detected in2010,4QTL on chromosome1Dtelo,2D,3A and4B in2011,3QTL onchromosome2D,3A and4B in mean value,4.85%-18.57%phenotype variation wasexplained by individual QTL.Four additive QTL for nitrogen uptake were dectected on chromosome1Dtelo,2D,3Aand4B by QTLNetwork2.0.3.71%-13.10%phenotype variation was explained by individualQTL. Significant additive×environment interactions were found on chromosome1Dtelo and3A, which explained3.01%and0.14%phenotype variation respectively. No epistasis QTLwere found for nitrogen uptake.According to the results of the two times of QTL detection, major and stable QTL for nitrogen uptake were on chromosome2D, the increasing alleles were from Cadenza. Someimportant genes which control nitrogen uptake probably were located on chromosome3A and4B. Cadenza plays the vital important role in improving nitrogen uptake.2. Plant height QTLUnder heigh nitrogen treatment, six QTL (on chromosome2D,3A,3B,4D,6A and6B)in2010, four QTL (on chromosome2D,3A,4D and6A) in2011, six QTL (on chromosome2D,3A,3B,4D,6A and6B) in mean value were detected by Windows QTL Cartographer2.5,3.02%-30.28%phenotype variation was explained by individual QTL. Six additive QTL weredetected on chromosome3A,4D,5A (2),6A and7A by QTLNetwork2.0,0.12%-4.1%phenotype variation was explained by individual QTL. One epistasis QTL (on chromosome5A-7A) was found, and explained0.23%phenotype variation, no epistasis×environmentinteraction was found.Under low nitrogen treatment, one QTL (on chromosome6A) in2008, six QTL (onchromosome2D,3A,3B,4D,6A and7BL) in2009and four QTL (on chromosome2D,3A,3B and4D) in mean value were detected by Windows QTL Cartographer2.5,4.44%-25.28%phenotype variation was explained by individual QTL. Five additive QTL were detected onchromosome2D,3A,3B,4D and6A by QTLNetwork2.0,1.37%-7.69%phenotype variationwas explained by individual QTL. No epistasis QTL was found under low nitrogen treatment.With the nitrogen treatments as environment factor, seven QTL were detected onchromosome2D,3A,3B,4D,5Atelo,6A and7D, significant additive×environmentinteractions were found on chromosome2D,3A,4D and6A. Two epistasis QTL weredetected on chromosome2D-3A and4D-6A, explained0.66%and0.52%phenotype variation,no significant epistasis×environment interaction was found.According to the results of the two times of QTL detection, stable plant height QTL waslocated on chromosome4D,3A and6A under high nitrogen treatment. The QTL onchromosome2D,5A and7A which detected by different softwares had different results underhigh nitrogen treatment, further study is needed. Stable plant height QTL was located onchromosome2D and4D under low nitrogen treatment. Major QTL was detected onchromosome4D under both high and low nitrogen treatments. The QTL on chromosome4Dprobably is Rht-D1b, and also control thousand grain weight and grain yield. The QTL onchromosome6A was expressed in special environment. Plant height was controlled by bothadditive and epistatic QTL, and affected by environments (different years and nitrogentreatments).3. Grain yield QTLOnly one QTL for grain yield was dectected on chromosome2D in2010by Windows QTL Cartographer2.5, which explained15.43%phenotype variation; Five (on chromosome1Dtelo,3A,4D,6A and6B) and four (on chromosome1Dtelo,3A,4D and6B) QTL weredetected in2011and mean value, respectively, explained4.93%-16.63%phenotype variation.Five additive QTL for grain yield were dectected on chromosome1Dtelo、3A、4D、6Band7A by QTLNetwork2.0. Significant additive×environment interactions were found onchromosome1Dtelo、3A、6B and7A, explained8.55%,7.82%,1.45%and1.59%phenotypevariation. No epistasis QTL were found for grain yield.According to the results of the two times of QTL detection, stable QTL for grain yieldwere on chromosome1Dtelo and4D. The QTL on chromosome4D is important for highyield breeding. There were main region for grain yield and related traits QTL on chromosome3A and6B. The QTL on chromosome2D was expressed in special environment. No epistasisQTL and epistasis×environment interaction were found4. Seedling root traits QTLThirty-four QTL for seedling root traits, shoot dry weight and root/shoot ratio weredectected, among them, nine QTL for root length were detected on chromosome3A,3B,4D,5BS and6A, explained6.03%-16.03%phenotype variation; nine QTL for root surface areawere detected on chromosome2A,2D,3A,3B,4D,5A and5BS, explained6.17%-12.82%phenotype variation;11QTL for root volume were detected on chromosome2D,3A,3B,4D,5A,5BS and6A, explained6.54%-13.52%phenotype variation; two QTL for root dry weightwere detected on chromosome2D and4D, explained8.65%and9.09%phenotype variation,respectively; two QTL for shoot dry weight were detected on chromosome4D and5A,explained34.50%and8.64%phenotype variation, respectively; one QTL for root/shoot ratiowas detected on chromosome4D, explained21.1%phenotype variation by Windows QTLCartographer2.5.Seminal axes root traits QTL were detected mainly on chromosome2D,4D and5A,lateral root traits QTL were detected mainly on chromosome3A and5BS, both lateral andseminal root traits QTL were detected on on chromosome3B and6A. The geneticmechanisms of seminal roots and lateral roots were different. The QTL on chromosome2D,3A,4D,5A and5BS were probably one QTL with pleiotropy effects. A new root QTL wasfound one chromosome4D.5. Relationship between nitrogen uptake, plant height, seedling root and grain yieldNitrogen uptake, plant hight, grain yield and seedling root traits were were closelyrelated, root surface area and volume were more important than root length to nitrogen uptakeand grain yield, it was opposite to plant height. The QTL on chromosome2D and3A could beused for improving root and nitrogen uptake breeding. The QTL on chromosome2D and4D which control root and plant height were one QTL with pleitropy or closely linkage. The QTLon chromosome6A which control root and plant height were closely linkage.Nitrogen uptake, plant height and some seedling root traits were significantly correlatedwith grain yield, nitrogen uptake and grain yield had the heighest correlation coefficient.Lateral root traits significantly and positively correlated with grain yield, bigger lateral rootsystem is benefit for high grain yield. Only on chromosome3A were mapped for all traits(nitrogen uptake, plant height, yield and some root traits), increasing allele was from Cadenza,which could be used for nitrogen uptake, plant height, root and grain yield improving. TheQTL on chromosome could be used for short height and heigh yield breeding.6. Effect of Rht genes on seedling rootRoot length, root surface area, root volume, total dry weight, root dry weight and shootdry weight were significantly reduced by Rht-B1c, Rht-D1c, Rht-12. Total root length, lateralroot length, lateral root were significantly reduced by Rht-8c. There were no significanteffects of Rht-D1b and Rht-B1b on root length, root surface area, total dry weight and shootdry weight. Rht-D1b significantly reduced root dry weight. But root length, root surface area,root volume, root dry weight, shoot dry weight and root/shoot ratio variation ranges of25short varities were similar to the variation ranges of23tall Watkins Collection varities, therewas no significant correlation between plant height and root traits in Watkins Collectionvarieties, which indicated the relationship between plant height and root is complicated,further study about it is needed.