Exploitation Of Gene Resources With High-yield And High Nitrogen Use Efficiency And Identification Of Excellent Germplasm In Wheat

Wheat(Triticuma estivum L.)is one of the most important food crops in the world.Improving the production capacity of wheat is urgently needed for global food security.Spikes per mu,grain number per spike and 1000-grain weight are the main components of wheat grain yield.The spike type,which is important determinant of grain number per panicle and grain weight,had the obvious effect on the yield.Therefore,it is of great significance to reveal the excellent genes in regulating the spike development of wheat,elucidate the mechanism and genetic network of them will greatly benefit the molecular breeding to increase the wheat yield by the optimization of spike type.In addition,it is the key to realize efficient ecological agriculture by improving fertilizer use efficiency especially nitrogen use efficiency(NUE).Consulting the research theories and results in rice to explore the gene resources that has great contribution to panicle type,grain yields and NUE in wheat,will provide theoretical reference for improving wheat spike traits and increasing grain yield and NUE.Short Panicle 1(SP1)was reported to be a key gene in regulating panicle branch development,and encoded a peptide transporter(PTR).In this study,we found that overexpression of SP1 led to increased grain yield and NUE in rice,SP1 has potential application for high NUE and yield breeding.Based on this,exploring the function of SP1 in wheat spike development and identifying its application potential in yield production will provide theoretical reference for improving wheat spike traits and increasing grain yield.In addition,for chlorate is an analogue of nitrate,chlorate sensitive plants tend to be have high nitrogen efficient characteristics.To identified germplasm resources of high nitrogen use efficiency,193 wheat landraces were used for screeing chlorate sensitivity.This will lay the foundation of improving wheat spike traits and nitrogen use efficiency.The main results are as follows:(1)We found that overexpression of SP1 led to increased grain yield and NUE in rice,which helps to develop new strategies for high yield and high NUE breeding in rice and other cereal crop;(2)We cloned the wheat homologous gene of rice SP1 Ta SP1-A/B/D,and define the features of Ta SP1 sequence through sequence alignment and phylogenetic tree analysis;(3)Obtained Ta SP1-B over-expression transgenic plants and constructed of Ta SP1 knockout vector;(4)Obtained a loss-of-function mutant of Ta SP1-A,sp1-a.Phenotype analysis of the sp1-a mutant showed that the plant height,spike length,spikelet number,grain width and1000-grain weight was decreased than those of the wild type.These results indicated that Ta SP1 has multiple effects on wheat plant architecture,which suggested that Ta SP1 may have functional differentiation with the rice SP1 gene;(5)We analyzed the expression pattern of Ta SP1 in varied organs by q RT-RCR.Ta SP1 derived from the ABD genome was expressed in all examined organs except roots,and showed highest expression in young spikes.Further analysis showed that expression of Ta SP1 was much lower in single-row stage.With the development of spikes,expression of Ta SP1 gradually increased and reached the highest in 0.5 cm spike.At the elongation stage of young spike,the expression of Ta SP1 decreased gradually.Besides,the expression of Ta SP1 showed higher expression in tiller buds and clum.These results indicated that expression pattern of Ta SP1 was consistent with the function of Ta SP1 in regulating spike and till development;(6)Ta SP1-A-GFP and Ta SP1-D-GFP localized on plasma membrane through transient expression in wheat protoplast system;(7)193 wheat landraces were used for screeing chlorate sensitivity,and we found that 3varieties were hypersensitive to potassium chlorate,namely varieties with high nitrogen use efficiency;8 varieties were much more sensitive to chlorate,namely varieties with higher nitrogen use efficiency.These results provided important clues for further mining the main effect QTL and germplasm resources for efficient nitrogen utilization.