Leaf Rust of Wheat: Pathogen Biology, Variation and Host Resistance

Abstract

Abstract:Rusts are important pathogens of angiosperms and gymnosperms including cereal crops and forest trees. With respect to cereals, rust fungi are among the most important pathogens.Cereal rusts are heteroecious and macrocyclic requiring two taxonomically unrelated hosts to complete a five spore stage life cycle. Cereal rust fungi are highly variable for virulence and molecular polymorphism. Leaf rust, caused by Puccinia triticina is the most common rust of wheat on a worldwide basis. Many different races of P. triticina that vary for virulence to leaf rust resistance genes in wheat differential lines are found annually in the US. Molecular markers have been used to characterize rust populations in the US and worldwide. Highly virulent races of P. triticina are selected by leaf rust resistance genes in the soft red winter wheat, hard red winter wheat and hard red spring wheat cultivars that are grown in different regions of the US. Cultivars that only have race-specific leaf rust resistance genes that are effective in seedling plants lose their effective resistance and become susceptible within a few years of release. Cultivars with combinations of race non-specific resistance genes have remained resistant over a period of years even though races of the leaf rust population have changed constantly.

Screening For Resistance Against Rust Diseases In Advanced Wheat (Triticum Aestivum L.) Genotypes

“…The screened material will be incorporated further in hybridization programs to create genetic variability against rusts. [29][30][31][32] …”

Rapid cloning of genes in hexaploid wheat using cultivar-specific long-range chromosome assembly

“…Leaf rust, caused by the pathogenic fungus Puccinia triticina is a widespread and devastating disease of wheat 11 that can be sustainably controlled by exploiting disease resistance that is present in some cultivars of this crop. The disease resistance gene Lr22a was crossed into hexaploid bread wheat (Triticum aestivum) from its wild relative Aegilops tauschii in the 1960s 12 .…”

Identification of Nine Pathotype-Specific Genes Conferring Resistance to Fusiform Rust in Loblolly Pine (Pinus taeda L.)

“…Currently (with additional loblolly pine selections and an additional Cqf isolate), we have data suggesting that at least four additional Fr genes exist, but these data were not presented as the Fr genes are as yet inadequately genetically mapped. Given the nine Fr genes that have been identified in the current work and data tentatively suggesting four additional Fr genes, this pathosystem may prove to be highly complex, similar to the cereal rust pathosystems reviewed by J. Kolmer [30]. In addition, because the pine-fusiform rust pathosystem has most likely coevolved for millions of years [47], the existence of numerous Fr genes seems probable.…”

“…This method is similar to that used in the cereal rust systems where a host-by-pathogen interaction is evaluated as incompatible (I) or compatible (C), although we inoculate segregating progeny instead of inbred lines (reviewed by J. Kolmer [30]). This fact required us to utilize genetic markers and mapping to differentiate multiple Fr genes within families, but also allows the simultaneous mapping of the Fr gene loci (discussed in Section 2.5).…”