ARS | Publication request: Resistance to Root Galling Caused by the Powdery Scab Pathogen Spongospora subterranea in Potato

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 15, 2008
Publication Date: November 15, 2008
Citation: Nitzan, N., Cummings, T., Johnson, D., Miller, J., Batchelor, D., Olsen, C., Brown, C.R. 2008. Resistance to Root Galling Caused by the Powdery Scab Pathogen Spongospora subterranea in Potato. Plant Disease. 92:1643-1649.

Interpretive Summary: Powdery scab is a complex disease of potato caused by a fungus. It can blemish tubers with scab-like lesions and impair the functioning of the roots by invading them, causing galls to form and by preventing the proper development of the roots. When the potato tops grow larger and encounter stress with the higher temperatures of mid-summer, the root systems cannot support the water needs of the tops and the crop ceases to grow. There is no good chemical remedy to this disease. Hence the need to breed resistant cultivars stands very high. We found that some advanced breeding materials and one variety in particular were resistant to root and tuber damage. It appears that the variety Summit Russet is quite resistant. The breeding materials that were examined all have one thing in common, they have Summit Russet as an ancestor in their breeding pedigree. Development of resistant varieties can prevent a yield and quality reduction of up to 25%. Powdery scab is a recent arrival in the Northwest. Rarely mentioned two decades ago, it has invaded most potato growing areas and now is present as a contaminant on almost all seed, as well as being already present in the soil of many fields.

Technical Abstract: Potato selections (clones and commercial cultivars) were examined for resistance to root galling, caused by the powdery scab pathogen Spongospora subterranea in 7 field trials conducted between 2003 and 2007 in the states of Washington (WA) and Idaho (ID). In 2003, Shepody demonstrated the highest level of susceptibility and was chosen as a susceptible standard. Every year selections less susceptible than Shepody were considered resistant and progressed to the next season. Selections that did not demonstrate resistance at least in two consecutive trials were discarded. In 2004, 16 of 23 selections, and 16 of 24 selections had fewer root galls than Shepody in WA and in ID, respectively. In 2005, 17 of 25 selections had fewer root galls than Shepody. In 2006, 27 of 37 selections had fewer root galls than Shepody; and in 2007, 21 of 23 had fewer root galls than Shepody. Twenty-four selections were more resistant to root galling than Shepody in 2 or more field trials. The selections PA95B2-4, PA98N5-2, PA98NM38-1, PO94A009-10 were more resistant than Shepody in 5 of 5 trials; PO94A009-7 in 4 of 4 trials; and the commercial cultivar Summit Russet in 2 of 2 trials. These selections also were ranked in the top 30% most resistant in 50-100% of the trials. These selections have the Mexican wild species Solanum bulbocastanum and the commercial cultivar Summit Russet appearing in their ancestry, which are the best explanation of their genetic source of resistance. The current study reported the presence of resistance to root galling caused by the powdery scab pathogen Spongospora subterranea.