| Stripe rust (caused by Puccinia striiformis Westend f. sp. tritici) is one of the most important diseases of wheat (Triticum aestivum L.) in the world. In China, epidemics of this disease occur periodically and caused destructive yield losses. Use of resistance cultivar is an effective, economical and environmentally-safe method for controlling this disease. Phenotypically speaking, there are two types of resistance in wheat to stripe rsut disease: hypersensitive response (HR) and quantitative resistance (QR). HR resistance, usually conferred by single or a few number of gene with major effect, is vulnerable to adaptation of P. striiformis, and consequently, is renderred susceptible by the fungus. Erosion of the HR gene results in shortage of resistance resources to stripe rust and it is needed to explore alternative resistance resources. QR, though being not immune from the disease, can reduce the intensity of the disease and reduce the application of fungicides. It was recognised that QR to stripe rust remained effective in some wheat cutivars that were widely grown for a long period of time in an environment favorable to the disease. This type of resistance, so-called durable resistance (DR), is of high value for sustainablly controlling the disease. Aquileja (AQ), Libellula (LB), Luke (LK), Nugaines (NG) and Xian Nong 4 (XN) posess DR to stripe rust. In the present study, the five cultivars were comparatively examined on their level of QR to stripe rust and on their DNA polymorphism by SSR and AFLP techniues. Two of the cultivars, AQ and XN, were studied on conventional inheritance of QR by assessing the disease intensity of parental, Fl, F2, backcross and F3 plants in the fields. The results are as follows:1. Compared with the susceptible cultivar MX, the five cultivars, AQ, LB, LK, NG and XN showed quantitative resistance to stripe rust to different extent. Their disease severities were one tenth to one fifth of that of MX. AQ, LK, and NG showed small size of lesion whereas the infection frequencies in them was not low. LB showed not only small lesion size but also low infection frequencies. The experimental errors of lesion length (LL), lesion width (LW), infection type (IT) and disease severity (DS) were smaller than those of lesion density (LD) and area under disease progress curve (AUDPC).2. 226 pairs of SSR primers were used to investigate DNA polymorphism of the five wheat cultivars. Of the 226 primer pairs, 117 showed polymorphism among the five cultivars. The 117 primer pairs revealed 398 alleles with the mean of 3.40. Alleles in genome B were more than those in genome A and D. Cluster analysis was done using average distance based on genetic distance of the five cultivars. Based on whole genome data, three groups were resulted: AQ and LB, NG and XN, and LK. It seemed that the clustered groups based on D genome data were related to geographical region where the wheat cultivars were collected and were related to pedigree of the cultivars. 36 pairs of AFLP primers; were used also to investigate DNApolymorphism of the five cultivars. 837 polymorphism bands were revdaled with the average of 23.25 per pairs of primer. Cluster analysis based on AFLP data was consistent with that of genome D data of SSR.3. One half to three forth of resistance phenotype variance of cvs. AQ and XN belonged to geneticvariance when crossed with susceptible cv. MX (except IT of cross MX/XN). The environmentvariance accounted one forth to one half of the total phenotype variance. The components ofgenetic variance differed from different crosses and items. The genetic variances of all the threeitems of cross MX/AQ were decided by additive effect only and no significant dominance andepistatic effect were detected. The genetic components of IT and DS of cross MX/XN wererelated to additive effect, dominance effect and additive-additive effect. The genetic componentsof AUDPC of this cross included additive effect and additive-additive effect. It was also noticedthat F2/F3 correlation coefficient of IT was not significant in cross MX/XN, i...
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