ARS | Publication request: An Update on Resistance to Powdery Scab

Submitted to: Potato Progress
Publication Type: Popular Publication
Publication Acceptance Date: February 15, 2008
Publication Date: July 11, 2008
Citation: Nitzan, N., Cummings, T., Johnson, D., Miller, J., Batchelor, D., Olsen, C., Brown, C.R. 2008. An Update on Resistance to Powdery Scab. Potato Progress. VIII p 3-5.

Technical Abstract: Powdery scab infections in the Columbia Basin occur early in the growing season when soil temperatures are relatively cool and irrigation water supplies the soil moisture needed for infection. Root galls usually appear 3 weeks after infection, which roughly correlates to 1.5 to 2 months past plant emergence. Most of the potato cultivars grown in the Columbia Basin are russet skin and do not commonly suffer from tuber lesions. However, their roots are susceptible to powdery scab and become severely infected. Reports indicated that root infection can lead to yield loss of 2-5 tons/acre. Damage to potato roots can potentially influence the development of large (>8oz) tubers needed for processing, resulting in the reduction of the useable potato yield. The management of powdery scab through resistant potato cultivars may be the most reliable and sustainable technique if resistance is high enough and stable. Seven field trials were carried out between 2003 and 2007 to select potato clones and cultivars (potato selections) with resistance to powdery scab development on roots (root galling). The trials were conducted in commercial fields located near Moses Lake, WA, and Parker, ID that have a history of powdery scab. In 2003 potato selections were examined for levels of root galls and Shepody was selected a susceptible standard. Between 2004 and 2007, 57 potato selections were tested for resistance to root galling at least once. Six selections: Summit Russet, PA98NM38-1, PA95B2-4, PA98N5-2, PO94A009-10 and PO94A009-7 were more resistant than Shepody to root galling. These selections performed significantly better than the industry standards R. Burbank, R. Ranger and Umatilla R., and were ranked among the top 30% in 50-100% of the trials (Table 1). These selections have two factors in common: 1) all are derived from an introgression program to incorporate resistance to the Columbia root-knot nematode Meloidogyne chitwoodi, from the Mexican wild species Solanum bulbocastanum; and 2) all have Summit Russet appearing more than once in the ancestry. Summit Russet is therefore the best explanation of the genetic source of resistance, and its origin of resistance to powdery scab will be investigated in future research. The identification of these resistant selections is a promising step towards a sustainable management of powdery scab. These selections have demonstrated high and stable resistance and have already been incorporated as parents in future breeding programs and as resistant standards in future screening trials. Currently, we are testing these selections in the greenhouse in an attempt to establish a rapid screening technique for powdery scab, which would hopefully correlate with the results from the field.