The Effect And QTL Mapping Of Traits Of Wheat On Seedling Stage Under Cd²⁺ Stress

With the rapid development of modern industry, heavy metal pollution has become animportant part of soil pollution. The heavy metal cadmium （Cd） is a kind of heavy metalwhich has more wide distribution and serious pollution degree. Cd in particular has attractedmuch attention due to its high mobility and toxicity. It has become one of the most threateningheavy metals to humans. Cd is not an essential nutrient in wheat growth and development, butit is easily absorbed by plants, and it can be highly toxic. When a certain amount accumulatesinside the wheat plants, they will produce poison to the plant. Wheat is the grain crop with thelargest planting area and highest total yield in the world. It is also the second-largest graincrop in China. Studying the effects of Cd on wheat is important to achieving high, stablewheat yields, to producing low-Cd wheat, and to ensuring grain product safety and the healthof Chinese citizens.In this study, we selected a population of168double haploid plants （DH） derived fromHuapei3and Yumai57, studying and analysising the effect of growth and development onwheat seedling stage under three Cd²⁺concentrations:0mg/L （control）,40mg/L, and120mg/L, and then used inclusive composite interval mapping （ICIM） to perform QTLmapping analyses on11development traits of wheat seedlings and roots under differentconcentration of Cd²⁺stress. The main results are as follows:（1）The growth of the wheat seedling and root were inhibited under Cd²⁺stress and thehigher the concentration is, the greater the inhibition is. The F value of variance analysisabout all traits in DH population was to significant level, indicating the presence of geneticdifferences. There are differences about the degree of inhibition on each trait of wheat. Themost serious degree of inhibition are stems dry weight and root dry weight, compared withcontrols, which were reduced by94.24%and93.91%respectively under120mg/L Cd²⁺stress.（2）There were differences for the correlation between all traits under0mg/L （controls）,40mg/L and120mg/L Cd²⁺stress. Compared with controls it was a very significant positivecorrelation between RV and RAD under Cd²⁺stress.There were no correlation between SLand RAD, RAD and RSA, RT and SFW. LA had no correlation with RTL、RSA、RV and RT too.It was significant positive correlation between RTL and SFW、RT and SDW. RADhad a very significant positive correlation with concentration and the correlation coefficient is0.754. SFW、SDW、SL、LA、RTL、RSA、RV、RT、RFW、RDW had negative correlationwith concentration respectively.（3）At three different Cd²⁺concentrations,43QTLs related to wheat growth anddevelopment during the seedling stage were mapped, and they were found to be distributed on14chromosomes:1A,1B,1D,2A,2B,2D,3A,3B,3D,6A,6B,6D,5D, and7D. Undercontrol conditions,22QTLs related to seedling and root development were mapped. Amongthese, the phenotypic variance was explained by qRTL1Bb, which was found to be related tototal root length, qRSA1Bb, related to root surface area, and qRT1Ba and qRT1Bb, related tonumber of root tips. Each of these QTL accounted for more than20%of correspondingphenotypic variation. These QTLs were not detected under Cd²⁺stress conditions, so theycould be considered Cd²⁺stress-intolerant genes and could be used in molecularmarker-assisted selection for large-rooted breeds of wheat. Under Cd²⁺stress conditions,21QTLs were mapped. Among these, qRAD3B and qSDW3Ba, located on chromosome3B,accounted for70.05%of the average root diameter and28.94%of the stem-leaf dry weight,respectively. These QTLs were of important research value; they could be considered closelylinked to Cd²⁺-tolerant genes and used in molecular marker-assisted selection forCd²⁺-tolerant traits. This study did not detect the same QTLs under control conditions orunder Cd²⁺stress conditions, suggesting that Cd²⁺stress can inhibit or induce the expressionof certain QTLs and genes.