Lesion Mimic And Quantitative Trait Loci For Adult-plant Resistance Against Yellow Rust In Common Wheat (T.aestivum)

Disease is one of the major barriers for stable and high wheat yield. Exploitation and utilization of resistance genes and breeding the resistant cultivars for wheat are considered as the most economical and effective method to control the disease. Wheat diseases can be divived into two groups, non race-specific resistance (horizontal resistance) and race special resistance (vertical resistance). Duo to the rapid evolution of disease physical races, special attentions were paid to non race-specific resistance. Some researches had revealed that majority lesion mimic were related to plant non race-specifict resistances. The lesion mimic phenotype was observed in wheat, maize and rice, but few researches were reported in wheat. The lesion mimics can not only enhance the resistance of crops to pathogens but also resulte in the yield reduction. So it has both theoretical and practical significance for the lesion mimic research. In addition, the adult-plant resistance (APR) against yellow rust is also associated with non race-specific resistance. So this research was focused on the lesion mimic and yellow rust APR in common wheat (T.aestivum), the results were shown as follows:1.In this study, some plants in thirteen populations from common wheat (T. aestivum) produced spontaneous lesions that can be divided into three types. The phenotype was light sensitive. Trypan blue staining as a histochemical indicator of cell death was performed on leaves expressing the lesions. Dead cells were stained deep blue at the necrotic sites whereas surrounding normal cells were unstained, which confirmed that the lesions were composed of dead cells. Because the pathogens could not be identified in the lesion mimic plants, it suggested that the lesion phenotype in this study was lesion mimic phenotype associated with PCD. Moreover, the 3',3'-diaminobenzidine (DAB) staining is an indicator that can detect not only on PCD but also on the development of PCD. It was proven that the cell death of lesion mimic was resulted firstly from the accumulation of H2O2 at the mesophll cell around the stomatal apparatus, then expansed surrounding cell and tissue, especially the vein. It was suggested that H2O2 may be transported by the vein to the whole plant and lead to the whole plant lesion mimic phenotype. Because H2Q2 involved in the resistance to disease, it was implied that the lesion mimic in this study could be associated with the disease resistance.2. The lesion mimics in three populations including Yanzhan 1/Hussar RIL (recombinent inbred line, RIL), Yanzhan 1/Lumai 14 RIL and Yanzhan 1/Zaosui 30 RIL were occurred stably in different environments. The genetic analysis indicated that the lesion mimics of three populations were all caused by duplicated interaction of recessive alleles derived from each parent. This was the first report that lesion mimic was resulted from two recessive alleles. One allele from Zaosui30 and the other from Yanzhanl were named lm1(lesion mimic 1) and lm2, respectively. The lm1 allele was flanked by microsatellite markers Xwmc674 and Xbarc133/Xbarc147 on chromosome 3BS, at genetic distances of 1.2 and 3.8 cM, respectively, whereas lm2 was mapped between microsatellite markers Xgwm513 and Xksuml54 on chromosome 4BL, at genetic distances of 1.5 and 3 cM, respectively. The linked markers we found laid foundation of marker-assisted selection and gene clone.3. Studies of Yanzhan 1/Zaosui 30 RIL in two cropping seasons showed that lesion mimic had less influence on the yield traits forming early, such as spikelet numbers, numbers of sterile spikelets per spike and grain numbers per spike, and affected mostly on the yield traits forming late, for example the one-thousand grain weight. And then, some lines with more highly expressed lesion mimic phenotypes exhibited significantly lower grain yields than those with normal phenotype, but no significant effects in the lines with low expressed lesion mimic phenotypes. The lesion mimic phenotype in this study was not associated with the seedling resistace but with the adult plant resistance to powdery mildew according to the seedling resistance identification in the greenhouse and adult-plant resistance identification in the field conditions.Yellow rust is the most damage to grain yields in cooler, wetter regions. It can even reduce the half of yield due to the immergence of spores at the early growing stage of plants. Owing to the use of limited sources of resistance and the variation of pathogens, many resistant cultivars lost the resistance. Breeding for resistant cultivars is considered as the most economical and effective way for controlling the disease. So the wheat breeding objective is exploitation and utilization of resistance genes and breeding the resistant cultivars for the wheat with stable and high yield. In this study, Neixiang188 and Yanzhanl were the commercial varieties in Henan province, and the Neixiangl88 is the one of main wheat varieties in Huang-Huai Area. A recombinant inbred line (RIL) population derived from a cross between the two cultivars was evaluated for adult-plant resistance (APR) in two years under field conditions using AUDPC (area under disease progress curve, AUDPC) and IT (infection type, IT).1. Base on the composite interval mapping, there was twenty-three QTLs detected which were located on sixteen chromosomes. Among them, nine additive QTLs were detected on seven chromosomes with five QEs (QTL×environment interactions, QEs). In addition, seven pairs of epistatic QTLs were identified on thirteen chromosomes with two pairs of epistatic QTLs showing QEs.2. The eleven QTLs effects based on AUDPC data explained 62.05% phenotype variation, with 44.32% additive effects,17.73% epistatic effects and 0.42% QEs. Using IT data, the five QTLs explained 37.53% phenotype variation, with 23.94% additive effects, 10.51% epistatic effects and 3.08% QEs.3. Using either AUDPC data or IT data, Two QTLs, QYr.caas-3D and QYr.caas-6A were both detected and two QTLs, QYrcaas-3B and QYrcaas-6D were the new loci of adult plant resistance to yellow rust.4. The loci of adult plant resistance to yellow rust were identified not only in resistant parent Neixiang 188 but also in susceptible parent Yanzhanl. The Neixiang188 explained 23.43%(AUDPC) and 17.92%(IT). Yanzhanl explained 20.89%(AUDPC) and 6.02%(IT).