Characterization and Genetic Analysis of Rice Mutant crr1 Exhibiting Compromised Non-host Resistance to Puccinia striiformis f. sp. tritici (Pst).

Jing Zhao,Yuheng Yang,Min Jiao,Junyi Wang,Yulin Cheng,Donghe Yang,Gangming Zhan,Kai Zhou,Lili Huang,Hongchang Zhang,Zhensheng Kang

doi:10.3389/fpls.2016.01822

Abstract

Wheat stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is one of the most devastating diseases of wheat in China. Rapid change to virulence following release of resistant cultivars necessitates ongoing discovery and exploitation of new resistance resources. Considerable effort has been directed at non-host resistance (NHR) which is believed to be durable. In the present study we identified rice mutant crr1 (compromised resistance to rust 1) that exhibited compromised NHR to Pst. Compared with wild type rice variety Nipponbare, crr1 mutant displayed a threefold increase in penetration rate by Pst, and enhanced hyphal growth. The pathogen also developed haustoria in crr1 mesophyll cells, but failed to sporulate. The response to the adapted rice pathogen Magnaporthe oryzae was unchanged in crr1 relative to the wild type. Several defense-related genes involved in the SA- and JA-mediated defense pathways response and in phytoalexin synthesis (such as OsPR1a, OsLOX1, and OsCPS4) were more rapidly and strongly induced in infected crr1 leaves than in the wild type, suggesting that other layers of defense are still in effect. Genetic analysis and mapping located the mutant loci at a region between markers ID14 and RM25792, which cover about 290 kb genome sequence on chromosome 10. Further fine mapping and cloning of the locus should provide further insights into NHR to rust fungi in rice, and may reveal new strategies for improving rust resistance in wheat.

Highlights

Wheat stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is a devastating disease of wheat worldwide (Wellings, 2011)
In the present study we identified rice mutant crr1 that allowed a high level of penetration rates by Pst and enhanced hyphal growth
To examine whether the production of H2O2 was defective in crr1, we examined the H2O2 production at infection sites in mutant and wild type plants challenged by Pst

Summary

INTRODUCTION

Wheat stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is a devastating disease of wheat worldwide (Wellings, 2011). The protein products of these PEN genes accumulate at sites of fungal penetration These genes contribute to R gene-mediated resistance and cell death in response to both adapted and non-adapted pathogens (Johansson et al, 2014). In the present study we identified rice mutant crr (compromised resistance to rust 1) that allowed a high level of penetration rates by Pst and enhanced hyphal growth. Upon infected by Pst crr showed strikingly enhanced expression levels of defense-related genes involved in the SA-, and JAmediated defense pathways as well as phytoalexin synthesis These observations suggested different molecular mechanisms underlying NHR to Pst in rice compared to the host resistance. Characterization and genetic study of crr would provide new insights into NHR, and assist in breeding wheat cultivars with durable resistance to stripe rust

RESULTS

DISCUSSION

Findings

MATERIALS AND METHODS