Elimination of common scab sensitive progeny from a potato breeding population using thaxtomin A as a selective agent

Abstract

Common scab is one of the most important soil-borne diseases of potato and is difficult to control. Selection of potato breeding lines for resistance to common scab is also cumbersome due to environmental factors influencing symptom development and an erratic spatial distribution of the scab pathogens (Streptomyces spp.) in the field. The bacterial phytotoxin thaxtomin A, which causes scab symptoms, can be used to screen large numbers of potato seedlings for tolerance in vitro, but few studies have investigated whether the results correspond to resistance to common scab observed in the field. In this study, 120 F1 potato progeny from a single cross were screened in vitro by exposing the seedlings to thaxtomin A added to the culture medium. Eighteen genotypes were selected based on high sensitivity or tolerance using shoot growth as the criterion, multiplied in vitro, and tested for resistance to common scab caused by S. turgidiscabies and S. scabies in a glasshouse and in three different fields. Evaluation of ca. 6500 tubers showed that the 18 potato genotypes differed in scab indices and disease severity (P < 0AE0001). The relative shoot height in vitro (thaxtomin A used at 0AE5 lg mL ) and the scab index in the field showed significant correlation (r s = )0AE463, P = 0AE0528, n = 18), also consistent with the results obtained under controlled conditions in the glasshouse. Hence, the in vitro bioassay may be used to discard scab-susceptible genotypes and elevate the overall levels of common scab resistance in the potato breeding populations.

Relationship Between the Application of Foliar Chemicals to Reduce Common Scab Disease of Potato and Correlation with Thaxtomin A Toxicity

“…This model may enable the development of a screening technique in which future collection of disease-based data could be minimized. These findings are supported by recent potato breeding work where thaxtomin A was successfully used as a selective screening agent to identify common scab sensitive progeny (12).…”

“…Bayesian models may enable the identification of one parameter to aid in the prediction of another related parameter. Thaxtomin A resistance is a key mechanism postulated for resistance to common scab (1,12,13,34,35) and its toxicity can be easily measured in a quick and rapid tuber slice assay (31). Its measurement and modeling in response to various chemical treatments may enable the efficaciousness of those treatments to be accurately assessed, without the need for expensive and time-consuming disease trials.…”

“…Its measurement and modeling in response to various chemical treatments may enable the efficaciousness of those treatments to be accurately assessed, without the need for expensive and time-consuming disease trials. In the case of common scab, sporadic disease intensities resulting from varied environmental influences can make assessing the effectiveness of given controls unpredictable (12,29). An initial assay could negate the need for assessment of disease (12) for assessing the likely suitability of a given control.…”

Phytotoxins produced by plant pathogenic Streptomyces species

“…; Hiltunen et al . ). This is significant given that CS is ubiquitous and notoriously difficult to effectively manage, and there are currently no potato cultivars that are completely resistant to the responsible pathogens (Dees and Wanner ).…”

Identification and Genetic Evaluation of a New Source of Pod Wart Resistance for Peanut (Arachis hypogaea L.)

“…Genetic resistance to PW may be another sustainable solution. In potato, for example, genetic resistance for common scab has been developed, mainly through somatic cell selection with thaxtomin A (Wilson et al, 2010; Hiltunen et al, 2011), as well as the existence of a certain degree of natural field resistance or tolerance (Pasco et al, 2005; Sedláková et al, 2013). All elite Virginia‐type cultivars of peanut are highly susceptible to PW and, in contrast to potato, no genetic resistance or tolerance for PW has been reported.…”