Heritability of resistance to common scab in diploid potatoes

Common scab, caused by several species of Streptomyces, is a serious soil-borne disease of potatoes that may cause superficial, raised or pitted lesions on potato tubers. Little is known about the genetic basis of resistance to this disease. The purpose of this study was to determine if genetic resistance to common scab exists in a diploid Solanum phureja-S. stenotomum (phu-stn) population and to estimate broad-sense (H) and narrow-sense (h ²) heritability for resistance to common scab. Two hundred seventy-one clones from a randomly mated phu-stn population were grown from 2003-2005 in naturally Streptomyces infested soil on a grower's field in Northampton Co., PA, in a randomized complete block design replicated twice. After harvest, the proportion of tubers with scab lesions was determined. The variable analyzed by the general linear models procedure in SAS using the maximum likelihood estimation method was the arcsine ( √ proportion of scabby tubers). There were significant differences among clones and the year x clone interaction was significant. H for resistance was estimated as 0.18 with a 95% confidence interval of 0.15 to 0.35. The clonal source of variation was partitioned into among families and within families. All the variation occurred within families. There was no additive genetic variance for resistance in this population, hence, h² was estimated as 0.00. Although levels of resistance to common scab cannot be improved by breeding in this diploid population, it may be feasible to transfer the high levels of resistance in this population to the tetraploid level via 4x-2x crosses.