Pathogenic streptomyces spp. Abundance affected by potato cultivars
Citation
Nahar, K., Goyer, C., Zebarth, B.J., Burton, D.L., Whitney, S. (2018). Pathogenic streptomyces spp. Abundance affected by potato cultivars. Phytopathology, [online] 108(9), 1046-1055. http://dx.doi.org/10.1094/PHYTO-03-18-0075-R
Plain language summary
Common scab of potato causes brownish lesions on potato tubers resulting in important economic losses every year in Canada. Potato cultivars can be very tolerant to common scab however none are completely resistant. The two most frequently found species causing common scab in North America are Streptomyces scabies and Streptomyces europaeiscabiei. Although it is known that potato cultivars vary in their tolerance to common scab, it is unclear how they affect Streptomyces species populations in soil over time. This study investigated the effects of potato cultivar on pathogenic (disease-causing) Streptomyces species abundance in three spatial locations in a common scab-infested field: 1) soil close to the plant; 2) root-zone soil; and 3) soil surrounding the tuber. Two tolerant (Gold Rush, Hindenburg) and two susceptible cultivars (Green Mountain, Agria) were tested. The results showed that the potato cultivars influenced the abundance of pathogenic Streptomyces species, probably because they changed soil properties in the root zone and around the tuber. There were five to six times more Streptomyces species in the root zone soil of susceptible cultivars compared with tolerant cultivars. Large quantities of potato roots are left to decompose in the soil after harvest thus cultivars that support greater populations of pathogenic Streptomyces species in the root zone soil may increase the load of pathogen inoculum that remains in agricultural fields at the end of a potato growing season.
Abstract
Potato cultivars vary in their tolerance to common scab; however, how they affect common scab-causing Streptomyces spp. populations over time is poorly understood. This study investigated the effects of potato cultivar on pathogenic Streptomyces spp. abundance, measured using quantitative PCR, in three spatial locations in a common scab-infested field: (i) soil close to the plant (SCP); (ii) rhizosphere soil (RS); and (iii) geocaulosphere soil (GS). Two tolerant (Gold Rush, Hindenburg) and two susceptible cultivars (Green Mountain, Agria) were tested. The abundance of pathogenic Streptomyces spp. significantly increased in late August compared with other dates in RS of susceptible cultivars in both years. Abundance of pathogenic Streptomyces spp., when averaged over locations and time, was significantly greater in susceptible cultivars compared with tolerant cultivars in 2014. Principal coordinates analysis showed that SCP and RS soil properties (pH, organic carbon, and nitrogen concentrations) explained 68 and 76% of total variation in Streptomyces spp. abundance among cultivars in 2013, respectively, suggesting that cultivars influenced common scab pathogen growth conditions. The results suggested that the genetic background of potato cultivars influenced the abundance of pathogenic Streptomyces spp., with five to six times more abundant Streptomyces spp. in RS of susceptible cultivars compared with tolerant cultivars, which would result in substantially more inoculum left in the field after harvest.