description
- Fusarium head blight (FHB) and wheat blast (brusone) are two devastating diseases of wheat that cause major yield losses in Brazil. Both pathogens severely affect wheat heads with direct damage to the grain, both in terms of quality and yield. In the absence of resistant varieties, current disease control relies heavily on fungicides that are costly, non-sustainable for Brazil, and only partially effective. Brusone, caused by the fungus Magnaporthe oryzae, was first identified in southern Brazil in 1985 but has since spread into Argentina, Bolivia, and Paraguay. The disease can cause total yield loss of yield and in 2009 brusone cut Brazilian wheat production by up to 30%. Importantly, the susceptibility of Brazilian varieties to brusone precludes their cultivation in the Cerrado region, an unused potential of 5 million ha for expansion that would improve Brazilian self-sufficiency of this essential staple. Fusarium head blight, caused primarily by the fungus Fusarium graminearum, is a serious disease in both Brazil and the UK. In addition to the very significant yield and quality losses, a major concern with FHB is the contamination of grain with trichothecene mycotoxins such as deoxynivalenol (DON). Both the European Union and Brazil have imposed maximum permissible levels for DON in cereals and cereal products. In Brazil, severe FHB outbreaks have increased in frequency. In 2014 FHB was so severe that more than 60% of wheat yield was lost in the State of Rio Grande do Sul and in the western region in 2014 some farmers lost more than 80% to the combination of brusone + FHB. There is an urgent need to identify and characterise sources of resistance to both FHB and brusone and ensure that the introduction of genes to control one disease does not compromise resistance to the other. Moderate levels of resistance to brusone have been identified in Brazilian wheat but the genetic basis of this resistance is unclear. Resistance expressed in seedlings is not always expressed in adult plants making it essential that resistance is assessed in adult plants. Resistance to FHB is generally controlled by several genes of moderate/weak effect that are defined genetically as quantitative trait loci (QTL). Although Brazilian wheat varieties differ widely in their resistance to FHB with some being moderately resistant, no variety was found to possess the major Fhb1 resistance originating from Asian sources. Thus the genetic basis of the most FHB-resistant Brazilian cultivars is not known and suggests that they contain novel resistances that could be combined with those from elsewhere to breed very highly resistant wheat varieties. This project will use a range of cutting-edge approaches to identify the genetic basis of resistance to brusone and FHB disease. We will identify which parts of the genome contain genes that increase FHB and/or brusone resistance and determine whether increased resistance to one disease is associated with increased susceptibility to the other. We will also identify genes in wheat that reduce resistance to the two diseases. This will provide a complementary approach to increasing resistance to FHB and brusone in wheat. We will produce DNA markers to enable plant breeders to follow the presence of the beneficial genes in their breeding programmes and ensure that their varieties are highly resistant to both diseases. The results from this work will benefit plant breeders in Brazil and elsewhere across the world where these diseases are prevalent. This should lead to reduced risk of crop losses to growers and reduced risk to consumers from mycotoxins accumulating in grain. It will lead to a reduced reliance on fungicides to control these diseases which, in turn will benefit, growers and the environment.