Study On Effect Of Developmental Characters In Wheat Seedling DH Lines And QTL Mapping Under Cr⁶⁺ Stress

Wheat is the most important food crop of the world. It has been an important missionthat speeding up the process of wheat breeding and improving wheat yield and quality bybiological technology.The wheat which grows in natural environment is always influenced bydifferent kinds of adverse factors,such as salt, drought, heavy metal, etc,especially heavymetal. Chromium （Cr） as one of industrial toxins, can cause deformity and mutation. Thehexavalent chromium harms wheat.Cr⁶⁺accumulated in wh-eat roots, stems and leaves notonly affects wheat growth, causing production drawd-own,but also enters into the food chain,endangering human health. At present chrome pollution is very serious in our country.A widerange of cultivated land is influenced by heavy metal, which leads to wheat yield and qualitydrawdown dramatically. QTL positioning of important traits and molecular markers exploringis the foundation of wheat quality molecular improvement. Therefore, We can clearlyunderstand chrome’ s toxic effect by studying its effect on wheat seedling growth and QTLpositioning, So as to forecast,evaluate and prevent chrome pollution, and provide theorybasis for cultivating wheat healthily and productively.This experiment takes indoor hydroponic method, uses a set of doubled haploid DH lines168single crosses derived from Huapei3×Yumai57, and studies the developm-entalcharacters of wheat seedlings under Chrome stress. Besides that we position the QTLs ofwheat seedling growth characters and analyze the interaction with environment, using geneticlinkage map constructed with SSR markers and Mixed-model Com-posite Interval Mapping.The results show that:（1） Wheat seedlings characters decrease with increment of Chrome concentration. Themost significant change is biomass, and the weight reduction of fresh roots and stems is moresignificant than the dry. Chrome has more obvious effect on roots comparing with seedlings.According to the formula of root length inhibition rate, the rates were37.96%and41.68%under Chrome stress.（2） There is very significant difference between different characters, the most is mainroot length. According to the regression equation for inhibition rate of root length we canconclude the semi-lethal and limited Chrome concentration of wheat seedling are125.38mg/L and280.36mg/L.（3） There is very significant correlation between wheat seedling characters.Under0mg/L Cr⁶⁺stress, in addition to the relativity between leaf age and seedling height is negative, theothers are positively related.Under40mg/L Cr⁶⁺stress, there’s no note-worthy relativitybetween leaf age and seedling height.the others have significant po-sitive correlation. Under120mg/L Cr⁶⁺stress, there’s very significant positive relat-ivity between various characters.The relativity between traits and concentration is negative.The order of correlation coefficientis: stem-leaf fresh weight, seedling heig-ht, leaf age, main root length, stem-leaf dry weight,Root dry weight and root fresh weight.（4）This experiment analyses7developmental characters of wheat seedling by co-mposite interval mapping method. A total of24additive QTLs and5pairs of epistatic QTLswere detected. The value of additive effect is between0.0055and0.4945, and thecontribution rate is between0.0045%and0.0631%. The value of epistatic effect is between0.0043and0.3885, and the contribution rate is between0.002%and0.013%.14are subjectedto environmental modifications.There are7additive QTLs and three pairs of epistatic QTLscontrolling wheat stem-leaf fresh weight, which is the most. And the7additive QTLs interactwith environment1, the two pairs of epistatic QTLs interact with environmental2andenvironmental3respectively. We havn’t detected additive QTLs controlling stem-leaf androot dry weight, nor epistatic QTLs contro-lling stem-leaf dry weight,leaf age,main rootlength and root dry weight. One reason maybe that some traits phenotypes will be influencedby the environment while the test is in a strict accordance environment.The other reason isthat the marks used to construct genetic map are not abundant enough. Some markscontrolling root traits have not been used to construct genetic map.So we still need to addmore marks, increase the map density, in order to detect more related QTLs.