Genomics also provides tools to investigate thoroughly a system of vegetative incompatibility (vic) that regulates hypovirus transmission among strains of C. Hypovirus infection also lends itself to the study of virulence factors, as comparative studies of isogenic strains that are or are not hypovirus infected may unravel the mechanisms by which virulence genes in the fungus are suppressed, ultimately leading to successful forest restoration. Incremental increases in blight resistance expressed by backcross generations of trees, coupled with diminished virulence provided by hypovirulent strains, may provide a viable integrated approach to blight control. Another consideration is the enhanced resistance of chestnut provided as part of the breeding initiative.
This is an important step for biological control.
parasitica strains they infect, thereby reducing pathogen virulence. Such efforts are expected to lead to development of molecular strategies that will enhance the effects that hypoviruses have on the C.
parasitica is a critical component of the genomics research. Understanding the roles different hypoviruses play in altering the virulence of C. parasitica with enhanced production of hypovirus-laden spores, thereby increasing the probability of hypovirus spread. Molecular approaches also provide mechanisms to develop genetically altered strains of C. For example, pathways for synthesis of secondary metabolites, which may serve as toxins and virulence factors, can be investigated more efficiently with access to the genome sequence. An important outcome of the work by genomics researchers in NE-1033 is the investigation of the fungus genome to learn what factors allow C. Genome sequencing has redefined the ability to test hypotheses relating to genes required in pathogens (for virulence) and hosts (for susceptibility). Technological advances have added new dimensions. Overcoming the challenges of utilizing hypovirulence as a tool for blight suppression, and ultimately for restoration of chestnut resources, is a driving force behind this project. Hypoviruses are being deployed in declining chestnut populations to test hypotheses of its spread, investigate within canker dynamics, and evaluate contributions of dying chestnut to hypovirulent inoculum. Ongoing studies are comparing aspects of recovering versus declining stands of chestnut in Michigan with the goal of determining why hypoviruses spread in some situations and not others. for biological control of the blight fungus has been problematic. But successful manipulation of hypovirus-infected strains in the eastern U.S. In areas of Michigan and Italy, hypovirulence appears to be the only explanation for the recovery from blight of significant stands of American and European chestnuts (16, 55, 67). Understanding its biology, ecology, and spread, as well as developing methods of manipulation, has been challenging. But the phenomenon of hypovirulence is complex. The discovery of hypovirulence rekindled interest in the blight fungus and brought renewed hope for chestnut restoration. The introduction of the exotic chestnut blight fungus to North America had unparalleled ecological and economic impacts, and functionally eliminated American chestnut from North American forests. The impetus for the regional project was the discovery of hypovirulent strains of the chestnut blight fungus, Cryphonectria parasitica, that afforded some level of resistance to the disease that had decimated chestnut resources in many parts of the world. NE-1033 began in 1982 as NE-140, a collaborative project that included five experiment stations.
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