ARS | Publication request: Effect of Isolate, Environment and a Defeated R-gene (RPi-ber) on Quantitative Resistance of Potato to Late Blight

Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 30, 2008
Publication Date: June 30, 2008
Citation: Rauscher, G.M., Mayton, H., Bonierbale, M., Simko, I., Smart, C., Grunwald, N.J., Fry, W. Effect of Isolate, Environment and a Defeated R-gene (RPi-ber) on Quantitative Resistance of Potato to Late Blight. American Phytopathological Society Annual Meeting, Minneapolis, Minnesota, July 26-July 30. Phytopathology 98:S130.

Technical Abstract: Phytophthora infestans, the causal agent of late blight is the most aggressive and costly pathogen affecting potato production worldwide. Genetic resistance is gaining importance as the pathogen continues to develop resistance to fungicides. However, little is known about the stability and specificity of quantitative resistance including the effects of defeated major resistance genes. In this study we analyzed resistance to P. infestans in two reciprocal inter-specific backcrosses of Solanum tuberosum and S. berthaultii. Analyses were done with five different strains of P. infestans. The experiments were conducted in different environments including field, plastic house and mist chamber. Inoculations were done by applying a suspension of sporangia to each plant, the percentage of the total tissue affected was scored every two or three days, and the area under the disease progress curve (AUDPC) was calculated. Phenotypic data was added as trait data for QTL mapping using MapManager QTX. We found a significant and lasting effect located in the same genetic position as a defeated R-gene (RPi-ber) in interactions with compatible P. infestans isolates. Out results also show quantitative resistance loci (QRLs) with a general effect (isolate nonspecific) in chromosomes III, V and X. Minor QRLs with isolate specificity were found scattered around the genome. These results are consistent with a lingering effect of a defeated R gene.