Capturing Multiple Disease Resistance in Wheat through Intergeneric Hybridization.

Dawn Chi,Colin Hiebert,Brent McCallum,George Fedak,Tom Fetch,Wenguang Cao,Allen Xue

doi:10.3390/biology10070631

Abstract

Simple SummaryProviding disease resistance in our crop plants is our ongoing exercise for plant pathologists/breeders/geneticists. Pathogens are continually evolving and releasing new variants. The variants arise through mutations or through sexual cycles on their respective alternate hosts. Thus, the search continues for unique genes for resistance. Another newer concept is the “pyramiding” of resistance genes. It has been shown that a cultivar may last only 3 years or so before being overcome by a new variant of the pathogen. The release of new cultivars with up to four resistance genes will delay their breakdown. In our ongoing work we have also produced pyramids containing a combination of resistance genes, including SrCad for resistance to new races of stem rust, Lr34, which is a major gene for resistance to leaf rust, and Fhb1, which is a common FHB QTL. This required the production of a series of doubled haploids (DH) to produce lines containing all four genes in reasonable-sized populations. A complex series of four-way crosses were required to generate the various gene combinations. In the studies reported here, the essential tools for marker-assisted-selection are produced, i.e., mapping populations containing the resistance genes and molecular makers assigned to each gene. It should be possible to simultaneously manipulate several resistance genes from existing genetic stocks without requiring complex cross combinations. Derivatives from 4 species from the secondary gene pool of wheat—1 diploid (T. monococcum), 2 tetraploid (T. carthlicum; T. timopheevi), and 1 hexaploid (T. miguschovae)—were screened for resistance to Fusarium head blight, leaf rust, stem rust, and stripe rust. Where screening, genetic studies, and mapping were completed it was shown that all species carried resistance to multiple plant diseases. Some derived lines carried resistance to up to four different diseases. Where mapping was completed, it was shown that different diseases mapped to different chromosomes within any one accession.

Highlights

The most important diseases of wheat (Triticum aestivum) in all temperate wheatgrowing regions of the world are the rusts caused by Puccinia triticina, P. striiformis, and P. graminis
In more detailed subsequent studies, using the 90K Infinium Select Chip as a marker system, Fusarium head blight (FHB) resistance QTL were detected on chromosomes 1A, 2A, 3A, and 6B, with the one on chromosome 1A being most consistent over environments [4]
Multiple disease resistance is a fairly common phenomenon and often can be traced to a single chromosome or chromosome translocation, especially when dealing with progeny from interspecific or intergeneric hybrids [13], For example an intact chromosome 6Ai #2 from Th. intermedium contributed resistance to leaf rust and powdery mildew and moderate resistance to stem rust and yellow rust when substituted for chromosome 6D of bread wheat [14]

Summary

Introduction

The most important diseases of wheat (Triticum aestivum) in all temperate wheatgrowing regions of the world are the rusts caused by Puccinia triticina (leaf rust), P. striiformis (stripe rust), and P. graminis (stem rust). Fusarium head blight (FHB), caused by Fusarium graminearum, has become a serious disease. It causes yield reductions and deposits a vomitoxin in the seed that is toxic to humans and other animals. Other common wheat diseases with a significant commercial impact on wheat production are powdery mildew

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