Influence of Thaxtomins in Different Combinations and Concentrations on Growth of Micropropagated Potato Shoot Cultures

Abstract

Plant-pathogenic Streptomyces species produce a variety of different phytotoxic 4-nitroindol-3-yl-containing 2,5-dioxopiperazines (thaxtomins) that induce scab symptoms on potato tubers (Solanum tuberosum). The possible mutual synergistic or antagonistic effects of thaxtomins are unknown. Modified methodology using column chromatography allowed the purification of thaxtomin A in large quantities (27 mg, HPLC purity of 97%). Thaxtomin A ortho isomer, thaxtomin B, and C-14 deoxythaxtomin B (thaxtomin D) were also purified. All four compounds induced similar symptoms of reduced root and shoot growth, root swelling (10-200 ppb), or necrosis (200-1000 ppb) on micropropagated in vitro cultures of potato. The scab-resistant potato cvs. Sabina and Nicola were more tolerant to thaxtomins than was the scab-susceptible cv. Matilda. Thaxtomins applied in combinations showed additive effects but no synergism, whereas thaxtomins A and B displayed antagonism with thaxtomin A ortho isomer.

Relationship of resistance to common scab disease and tolerance to thaxtomin A toxicity within potato cultivars

“…others to use thaxtomin A as a screening tool during conventional breeding to identify lines with enhanced toxin tolerance, with the expectation that these will have greater resistance to disease (Acuña et al 1998;Delserone et al 1991;Hiltunen et al 2006). …”

“…1). Few studies have reported on potato varietal or cultivar susceptibilities to thaxtomin A (Delserone et al 1991;Acuña et al 1998;Hiltunen et al 2006). They reported positive associations between common scab disease resistance and thaxtomin A toxicity in potato shoots (Acuña et al 1998;Hiltunen et al 2006) and tuber tissues (Delserone et al 1991).…”

“…Few studies have reported on potato varietal or cultivar susceptibilities to thaxtomin A (Delserone et al 1991;Acuña et al 1998;Hiltunen et al 2006). They reported positive associations between common scab disease resistance and thaxtomin A toxicity in potato shoots (Acuña et al 1998;Hiltunen et al 2006) and tuber tissues (Delserone et al 1991). In contradiction to these reports we have shown that extent of resistance to common scab disease measured across nine cultivars (in three separate trials) was not associated nor showed any consistent pattern of association with the levels of tolerance to thaxtomin A toxicity.…”

Genetic and physiological determinants ofStreptomyces scabiespathogenicity

“…, 1992; Fig. 2), although phytotoxicity has also been reported for other thaxtomins (Hiltunen et al. , 2006; King and Lawrence, 2001).…”

Antimycin A-producing nonphytopathogenic Streptomyces turgidiscabies from potato

“…Both species produce phytotoxic compounds, thaxtomins (Bukhalid et al. 1998; Ylhäinen 2001; Hiltunen et al. 2006), which is essential for the induction of the characteristic scab symptoms on potato tubers (King et al.…”