Submitted to: American Journal of Potato Research
Publication Type: Abstract Only
Publication Acceptance Date: 1/1/1999
Publication Date: N/A
Citation: Interpretive Summary: Common scab can be a serious problem in some potato fields. It was found previously that the bacteria that causes this disease produces a toxin. Varieties that were resistant to scab in the field were also resistant to the purified toxin called Thaxtomin A. This research developed a procedure that uses this purified toxin to screen potato seedlings in tissue culture. Seedlings that survived when exposed to the toxin in tissue culture media were resistant to common scab in the field. The toxin can be a useful tool for selecting scab resistant potato germplasm.
Technical Abstract: Thaxtomin A (TA) produced by pathogenic Streptomyces scabies strains is one of the major factors involved in common scab development. True potato seed (TPS) from self crosses of Ranger, very susceptible, and Nooksack moderately resistant, and crosses of Ranger by Nooksack were germinated on agar containing 0 or 1uM of TA for 7 days at 20 C. Seedlings were rescued from 1uM TA. Random seedlings were also rescued from 0uM TA. These seedlings were multiplied in tissue culture and plants that were transplanted to miniplots with scab infested field soil. At harvest tubers were evaluated for scab symptoms. A higher percentage of plants (50 percent) from TA selected seedlings had tuber scores lower or similar to Nooksack compared to plants from non TA selections (29 percent P 0.05.) Minitubers of TA selected seedlings previously tested in miniplot field soil from selfcrosses of Ranger, Nooksack and Atlantic were planted in scab binfested soil field conditions as a second year trial 1998. These plants produced tubers with scab scores lower than Ranger 6.0, being mainly similar to or lower than Nooksack 2.6, P 0.05. We identified two Ranger progenies with scores of 1.0 and 1.8 and two Atlantic progenies with scores of 0.5 and 1.8. We conclude that Thaxtomin A is a useful tool for selection of scab resistant germplasm.