Genetic Analysis Of Cold Tolerance Traits And QTL Identification At Booting Stage Of Japonica Rice

Rice is a crucial food crops in the world, which occupies a pivotal position in China’s totalgrain outputs. Although Heilongjiang province is a main production area of Japonica rice, it isalso a high incidence region of chilling injury. Booting stage is the most sensitive period to thechilling injury in the whole growth period that might cause lost of yield. Breeding and usingcold tolerance cultivar is suitable for cold cultivated regions which can avoid the injury of colddamage. In recent years, with the rapid development of molecular marker techniques, combinedwith construction of high density genetic map in rice with suitable statistical analysis methods,QTLs for the cold torlerance traits in various growth stages of rice has been extensitivelydetected at home and abroad. However, the research of cold resistance in japonica ricecooperating with method of genetic analysis and quantitative mapping is rarely reported. Toinvestigate the genetic architecture of cold tolerance, F₁-F₄generation derived from a crossbetween japonica cultivar Dongnong422with high yield and quality and Kongyu131with coldtolerance cultivated in Heilongjiang province were used as experiment materials forconstructing genetic linkage map and detecting QTLs underlying cold tolerance related traits atbooting stage. All the above studies were conducive to provide theoretical basis for coldtolerance molecular marker assisted breeding in rice. The results are as follows:1、Under the condition of cold water irrigation, the phenotypic values and cold responseindex （CRI） of number of productive ear （NPE）、length of main ear （LME）、primary branchnumber （PBN）、secondary branch number （SBN）、number of total grain per ear （NTGP）、ripening rate （RR） and grain weight per plant （GWP） at booting stage of rice followed normaldistribution with a single peak in F_3:4lines, considering that these phenotypic characters werethe quantitative traits and were controlled by major and multiple genes, which were suitable forQTL mapping.2、Correlation analysis showed that SBN、RR and GWP were impressionable under coldwater stress.These cold-tolerant related traits were the vital index of chilling injury at bootingstage of rice in cold.3、Analysis on the genetic progress and heritability for F₄lines displayed that:GWP＞SBN＞RR＞PBN＞NTGP＞NPE＞LME.4、Seperation and genetic analysis of rice cold toleranceThe optimum genetic model of cold-tolerant related inheritance traits of NPE, NPECRI, LME, PBN, PBNCRI, NTGP and GWP were D-0model, which were influenced by oneadditive-dominant major genes plus additive-dominant-epistatic polygene. The polygeneheritability was much lower than the rate of the major gene, considering that the above traitswere mainly genetic-based.But the heritability of GWP was mainly polygene-based.The optimum genetic model of cold-tolerant related inheritance traits ofSBNCRI,NTGPCRI and GWPCRI were D-2model, which were effected by one additive majorgenes plus additive-dominant polygene. The polygene heritability was much lower than the rateof the major gene,considering that the above traits were main genetic-based.The optimum genetic model of cold-tolerant related inheritance traits of LMECRI was D-4model,which was impressed by one negative completely dominant major genes plusadditive-dominant polygene. The polygene heritability was much lower than the rate of themajor gene,considering that the trait of LMECRI was main genetic-based.The optimum genetic model of cold-tolerant related inheritance traits of SBN and RRCRIwere E-1-0model,which were influenced by two additive-dominant-epistatic major genes plusadditive-dominant-epistatic polygene. The polygene heritability was much lower than the rate ofthe major gene,considering that the above traits were main genetic-based.The optimum genetic model of cold-tolerant related inheritance traits of RR was E-1-2model, which was controlled by two additive-dominant major genes plus additive-dominantpolygene.The polygene heritability was much lower than the rate of the main geng,indicatingthat the trait of RR was main genetic-based.5、A genetic linkage map including105SSR molecular markers was constructed and drawnby IciMapping and MapChart2.1software. The linkage map was about1923.90cM in lengthand the average distance between markers was18.32cM.6、A total of62QTLs associated with NPE, LME, PBN, SBN, NTGP, RR, GWP and theirrelated cold response index in F_2:3and in F_2:4population at booting stage under cold watercondition were detected.Under the condition of two generations,13QTLs controling the abovetraits were found.All the QTLs sites were located on chromosomes2,3,5,6,7and12respectively. The LOD value was ranged from2.51to14.37. The contribution of QTLs wasranged from2.74%to37.78%...