Breeding for Resistance to Bacterial Wilt in Ryegrass: Insights into the Genetic Control of Plant Resistance and Pathogen Virulence
Bacterial wilt caused by Xanthomonas translucens pv. graminis (Xtg) is a severe disease of forage grasses leading to drastic losses in pure and mixed stands. Italian ryegrass (Lolium multiflorum) is particularly susceptible to bacterial wilt and breeding for resistance is the only practicable means of disease control. A detailed understanding of the genetic control of this complex host-pathogen interaction is indispensible for the further development of L. multiflorum cultivars with increased resistance to bacterial wilt and to refine and optimise breeding procedures. While several recent studies have revealed novel insights on plant resistance, little is known about the processes involved in host-colonization and disease development. Therefore, factors influencing pathogen virulence were investigated in Xtg using conserved primer approaches and whole genome sequencing. Knock-out mutation of components of the type three secretion system (T3SS), a major virulence factor in many Xanthomonas spp., showed that the T3SS is important for Xtg virulence but not for in planta multiplication. Analysis of the draft genome sequences revealed a substantial number of effectors apparently characteristic for Xtg. In conlusion, our investigations on the Xtg x L. multiflorum interactions provide fundamental insights for the development of innovative resistance breeding approaches.
KeywordsQuantitative Trait Locus Simple Sequence Repeat Marker Insertion Sequence Major Quantitative Trait Locus Bacterial Wilt
This research was supported by the Swiss National Science Foundation (Grant No. 31003A–112582). We thank C. Conradin for her work on ΔhrpG mutants and S. Reinhard, S. Kuhnen and P. Streckeisen for excellent technical support.
- Ramalingam J, Cruz CMV, Kukreja K, Chittoor JM, Wu JL, Lee SW, Baraoidan M, George ML, Cohen MB, Hulbert SH, Leach JE, Leung H (2003) Candidate defense genes from rice, barley, and maize and their association with qualitative and quantitative resistance in rice. Mol Plant Microbe Interact 16:14–24CrossRefGoogle Scholar
- Salanoubat M, Genin S, Artiguenave F, Gouzy J, Mangenot S, Arlat M, Billault A, Brottier P, Camus JC, Cattolico L, Chandler M, Choisne N, Claudel-Renard C, Cunnac S, Demange N, Gaspin C, Lavie M, Moisan A, Robert C, Saurin W, Schiex T, Siguier P, Thebault P, Whalen M, Wincker P, Levy M, Weissenbach J, Boucher CA (2002) Genome sequence of the plant pathogen Ralstonia solanacearum. Nature 415:497–502PubMedCrossRefGoogle Scholar