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Oral: Promising Phenotyping Efforts for Understanding Genetic and Molecular Bases of Plant Disease Resistance


Phenotyping for resistance to viruses in maize
M. REDINBAUGH (1), J. Zambrano (2), M. Jones (3), D. Francis (4), R. Louie (3) (1) USDA- ARS Corn, Soybean and Wheat Quality Research, U.S.A.; (2) INIAP, Ecuador; (3) USDA, ARS CSWQRU, U.S.A.; (4) Ohio State University, U.S.A.

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The great strides made in sequence and genotypic analysis in maize have facilitated rapid identification of genes and quantitative trait loci (QTL) in maize, but identifying virus resistance genes and QTL continues to require high efficiency screening protocols that allow identification and evaluation of resistant plants. Over the last 40 years researchers in the USDA, ARS - Ohio State University maize virus research program have used natural infection, leaf rub inoculation (VPI), air brush, backpack sprayer, solid stream protocols, vascular puncture inoculation, and viruliferous insects to (i) screen germplasm collections to identify resistance sources; (ii) identify markers linked to genes or QTLs conferring resistance; and (iii) introgress resistance into elite breeding lines. Mechanical transmission, VPI and insect transmission were used to characterize resistance to each of nine viruses in six virus families in the multiply virus resistant inbred line, Oh1VI. Depending on the virus, dominant, recessive, or additive gene effects were responsible for the resistance observed, and resistance was associated with one to three loci. Major clusters of resistance genes were identified in specific regions of chromosomes 2, 3, 6, and 10. It is unknown whether these QTL clusters contain single or multiple virus resistance genes, but close linkage of resistance loci in this line could facilitate development of virus resistant crops.