Somaclonal selection in potato for resistance to common scab provides concurrent resistance to powdery scab

Abstract

Variant somaclones of potato cultivar Russet Burbank, selected for resistance to common scab using in vitro cell selection techniques, were tested for resistance to powdery scab, another important disease of potato caused by Spongospora subterranea. This pathogen also invades roots, producing root galls. Most variants consistently showed increased resistance to powdery scab, both in field and glasshouse challenge, when compared to the parental cultivar, several significantly so. On average, the best variant reduced powdery scab incidence by 51% and severity (tuber surface coverage) by 64%. In contrast, no improvement in the extent of root infection and root galling was seen. These results suggest host interactions during root and tuber infection are distinct. Correlation analyses of disease indices amongst the selected variants showed no association between Sp. subterranea root infection and gall scores, nor between root infection and tuber disease severity. However, a weak positive association was found between root gall score and tuber disease, and a strong correlation between tuber disease incidence and severity scores. Interestingly, positive correlations were also found between the extent of powdery and common scab resistance expressed and both incidence and severity of these diseases within the variants, suggesting a common defence mechanism. The role of thaxtomin A in selecting for concurrent resistance to both diseases is discussed.

Root infection of potato by Spongospora subterranea: knowledge review and evidence for decreased plant productivity

“…The demonstrated differences in potato cultivar responses to the three Spongospora diseases confirm that host reaction to the diseases differs in different germplasm lines (see also Falloon et al ., ; Nitzan et al ., , ; Tegg et al ., ). This suggests that efforts to provide comprehensive resistance to S. subterranea through plant breeding and selection will need to take account of all stages of the pathogen life cycle on host plants.…”

“…The root infection stages of the pathogen life cycle were recognized later, and the potentially deleterious effects of these stages on plant productivity have only been suggested much more recently. There is now a strong consensus that Spongospora root galling and tuber powdery scab are not related diseases (Falloon et al ., ; van de Graaf et al ., ; Nitzan et al ., ; Merz et al ., ; Hernandez Maldonado et al ., ; Tegg et al ., ), other than through the causative pathogen.…”

Applications of biotechnology and genomics in potato improvement

“…Thaxtomin A can induce disease symptoms in the absence of Streptomyces (Lawrence et al, 1990), and increased resistance to thaxtomin A in cultured potato seedlings has been correlated with decreased incidence of scab lesions on tubers (Hiltunen et al, 2006). Somatic cell selection for resistance to thaxtomin A in potato cell cultures enabled the recovery of plants with improved resistance to common scab (Tegg et al, 2013;Wilson et al, 2009Wilson et al, , 2010. This disease resistance was achieved in elite clones and retained in field evaluations (Tegg et al, 2013;Wilson et al, 2010).…”

“…Somatic cell selection for resistance to thaxtomin A in potato cell cultures enabled the recovery of plants with improved resistance to common scab (Tegg et al, 2013;Wilson et al, 2009Wilson et al, , 2010. This disease resistance was achieved in elite clones and retained in field evaluations (Tegg et al, 2013;Wilson et al, 2010).…”

Modeling Pathogen DNA Content and Visual Disease Assessment in Seed Tubers to Inform Disease in Potato Progeny Root, Stolon, and Tubers

“…In Australia, three major diseases affecting potato tuber produc tion and quality are black scurf, common scab, and powdery scab (30,32,40), caused by infections with the pathogens Rhizoctonia solani Ktihn AG3, Streptomyces scabies (Thaxter) Lambert & Loria, and Spongospora subterranea (Walk.) Lagerh.…”