Characterization of Yr15 resistance to stripe rust of wheat

[摘要] English: Stripe (yellow) rust, caused by Puccinia striiformis Westend f. sp. tritici,is a major disease of bread wheat, Triticum aestivum L., in SouthAfrica. The objective of this study was to evaluate the Yr15 gene as apotential resistance source for breeding purposes.Histological evidence was provided that Yr15 conditions ahypersensitive reaction typical of non-durable resistance.Fluorescence, phase contrast and scanning electron microscopycomplemented each other and may be used to quantify variousaspects of resistance expression in the wheat stripe rust pathosystem.The frequency of stomatal penetration was extremely low and nomeaningful differences in early infection structures were observedbetween the resistant Yr15 and susceptible Avocet 'S' lines. Papillaewere not involved in the resistance response to pathotype 6E16.In studies of defense-related proteins, an induction of β- 1,3-glucanaseactivity in both resistant and susceptible wheat genotypes wasdetected within 96 h post-inoculation (hpi). This induction, however,was constitutive and did not depend on the infection process. Likewise,no changes in chitinase activity were observed between resistant andsusceptible plants. A pronounced increase of peroxidase activitybetween 0 and 168 hpi, in both infected and uninfected resistant andsusceptible plants was observed, suggesting a constitutive expressionof this enzyme.Using AFLP (Amplified Fragment Length Polymorphism) technology todetect possible molecular markers for Yr15, two primer combinationsyielded polymorph isms between the bulked susceptible and resistantSST55 x Yr15/6*AvS F2 DNA, as well as between the susceptible andresistant parents. Fragment sizes ranged from 50 to 420 bp. Of these,one 95 bp fragment identified using primers MseCAA + Eco-ACA andone 205 bp fragment identified using primers MseCAA + Eco-AACwere detected in the resistant parent and the resistant F2 group. Thisindicates that these fragments are closely associated with Yr15 makingthem ideal candidates for further investigation.

[发布机构] University of the Free State