Author
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Brooks, Steven |
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Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 4/23/2007 Publication Date: 10/1/2007 Citation: Brooks, S.A. 2007. Sensitivity to a phytotoxin from Rhizoctonia solani correlates with sheath blight susceptibility in rice. Phytopathology. 97:1207-1212. Interpretive Summary: The purpose of the work presented in this manuscript is to describe a new method to screen for sheath blight resistance in rice. Limited control for this disease has been achieved thru traditional breeding and screening methods. The primary limitation to any analysis of sheath blight resistance has been accurate disease ranking. The disease is highly influenced by unrelated plant traits (such as plant height) and the environment. The new method exploits a known virulence factor produced by the pathogen, which is a host-selective toxin. By using the purified toxin in place of the pathogen, all confounding disease factors are circumvented and an accurate phenotype is obtained. Sensitivity to the toxin is positively correlated with disease susceptibility, allowing the toxin to be used for eliminating susceptible germplasm and mapping toxin sensitivity genes. In this manuscript we describe the new method directly, and its utility for identifying disease susceptible germplasm. Furthermore, we describe the genetic regulation of toxin sensitivity and the ability to identify the corresponding genes. Technical Abstract: Sheath Blight is widely regarded as one of the most important diseases of cultivated rice and germplasm improvement is essential for disease management. Genetic sources of tolerance for this disease are known, however, complex quantitative inheritance and high environmental variability make phenotypic evaluation difficult. To circumvent these confounding factors we have developed a method to evaluate the RS-toxin component of the pathosystem, to help elucidate genetic tolerance to this disease. RS-toxin is host-selective and can be purfied from cultures of the necrotrophic pathogen Rhizoctonia solani. Infiltration of the toxin into rice plants reproduces necrotic symptoms typical of Sheath Blight lesions. RS-toxin assays are non-destructive to rice plants and quickly produce reliable, replicable data. A differential response to toxin infiltration has been observed in rice cultivars, and toxin sensitivity is inherited as a dominant gene. The methods presented allow rapid and reproducible phenotypic evaluation, and the effects of toxin sensitivity on disease susceptibility are discussed. |
