| Wheat(Triticum aestivum L.）is one of the major food crops. Drought and phosphorusdeficiency in soil are major factors limiting high and stable yield of wheat. Drought andlow-phosphorus tolerance are all complex quantitative traits controlled by polygenes withminor effects, and it is difficult to conduct intensive study by traditional cytogenetics andquantitative genetics. Using three related F9recombinant inbred line (RIL) populations asmaterials, unconditional and conditional QTL analysis of seedling traits related to drought andlow-phosphorus tolerance in wheat were conducted in this paper. Aim was to explicit theposition and the effect of loci concerned with drought and low-phosphorus tolerance in wheat,and reveal the genetic relationship between drought and low-phosphorus tolerance andseedling traits at the QTL level，respectively. It would be important for the geneticimprovement of wheat for increasing drought tolerance and efficient utilization of phosphorus.At the same time, a new genetic map based on PCR-based molecular marker and singlenucleotide polymorphism (SNP) was constructed using another RIL population derived fromcrossing between Weimai8and Ji8901as material. Aim was to make it integrate with otherthree genetic maps constructed by our lab and take foundation for multi-population jointlyQTL analysis of agricultural traits in wheat. The main results were as follows:(1) Conditional and unconditional analysis of8traits of wheat seedling—coleoptilelength (CL), plant height (PH), the longest root length (RL), root number (RN), seedling dryweight (SDW), stem-and-leaves dry weight (SLDW), root dry weight (RDW), root-to-shootdry weight ratio (RSDWR)—were conducted under two water conditions using three F9RILpopulations.Total of121QTLs located on all of the21chromosomes of wheat were detected,accounting for2.12-28.56%of phenotypic variance respectively. All of them,71were majorQTLs with a contribution rate greater than10%. Eighty seven QTLs were detected byunconditional QTL analysis. All of them,12were detected in more than one population,18were simultaneously detected under the two water conditions,38were detected under onlynormal water condition, and31were detected only under drought stress condition. Total34 QTL related to drought tolerance of seedling were detected. Only8QTL were also detectedby unconditional analyses of the seedling traits under drought stress condition. It indicatedthat conditional QTL analysis could exclude effectively the influence of normal expressioneffect of trait to detect QTL really related to drought tolerance. Eleven important QTL clusterslocated on chromosome1BL,1D,2A,2B,2D,4A,6B, and7B were discoved. All of them,9included QTLs detected in more than one population, and8included QTLs related to droughttolerance by conditional QTL analysis. It indicated that these chromosomal intervals withQTL clusters should be important areas controlling the expression of seedling traits related todrought tolerance.(2) Conditional and unconditional QTL analyses of the12traits of wheatseedlings—plant height (PH), the longest root length (RL), root number (RN), seedling dryweight (SDW), stem-and-leave dry weight (SLDW), root dry weight (RDW), stem and leavephosphorus utilization efficiency (SLPU), root phosphorus utilization efficiency (RPU), shootphosphorus utilization efficiency (SPU), stem and leave phosphorus content (SLPC), rootphosphorus content (RPC), shoot phosphorus content (SPC)—were conducted under normalphosphorus and low-phosphorus conditions using three F9recombinant inbred line (RIL)populations. Total of159QTLs located on the21chromosomes of wheat were detected,accounting for4.04-71.12%of phenotypic variance respectively. All of them,105were majorQTLs with a contribution rate greater than10%. One hundred and ten QTLs were detected byunconditional QTL analysis. Among of these QTLs,19were detected simultaneously in twopopulations,10were detected simultaneously under two phosphorus conditions,38weredetected only under normal phosphorus condition, and48were detected underlow-phosphorus condition. Total of54QTLs related to low-phosphorus tolerance of seedlingwere detected. Only10QTLs were also detected by unconditional analysis of seedling traitsunder low-phosphorus condition. It indicated that most of the QTLs detected by unconditionalQTL analysis of seedling traits under low-phosphorus condition were only concerned withexpression of these traits, but not concerned directly with low-phosphorus tolerance. Sixteenimportant QTL clusters located on chromosome1D,2A,2B,3A,3B,4B,4D,5A,5D,6A, and6B were discovered. All of them,4included loci detected in WL, WY, and WJ threepopulations,10included loci detected in two populations, and10included loci related tolow-phosphorus tolerance. It indicated that these chromosome intervals with these QTLclusters should be important areas controlling the expression of seedling traits related tolow-phosphorus tolerance.(3) A genetic map comprising3916marker and1257loci were constructed based on PCR-based and SNP molecular markers using the recombinant inbred line (RIL) populationderived from crossing of Weimai8and Ji8901. The genetic map spaned2291.6cM, with anaverage density of one marker per1.82cM. Due to the linkage distance>50cM between theadjacent loci, there was a linkage gaps in chromosome2A. A genome included541loci andspaned925.9cM, with an average density of one locus per1.71cM. B genome included574loci and spaned899.1cM, with an average density of one locus per1.57cM. D genomeincluded142loci and spaned466.6cM, with an average density of one locus per3.29cM.(4) Three important QTL clusters were detected simultaneously in both drought toleranceand low-phosphorus tolerance trials of wheat seedling. The first QTL cluster located onchromosome1D between wpt-67199and Xwmc429.3, related to drought tolerance,low-phosphorus tolerance, RL, RN, RPUE, SPC, and SLPC. The second QTL cluster locatedon chromosome2B between Xbarc55.1and wpt-3561, related to drought tolerance,low-phosphorus tolerance, RN, SPUE, SLPUE, SPC, SLPC, SDW, and SLDW. The thirdQTL cluster located on chromosome7B between wpt-669158and wpt-666615, related todrought tolerance, low-phosphorus tolerance, SPUE, SPC, SDW, and SLDW. These threeQTL clusters could be detected by QTL analyses of different population, differentenvironment, different growth and development stage, and different trait, which indicated thatthese three QTL clusters could have significant influence in the growth and development ofwheat and it is necessary to conduct more intensive study. |
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