A comparison ofCorynebacterium sepedonicum inocula from resistant and susceptible potato varieties

Abstract

Experiments were conducted in 1946 and 1947 to determine whether or not ring-rot bacteria,Corynebacterium sepedonicum, from resistant potato seedlings and varieties were more pathogenic than those from susceptible varieties. Bliss Triumph, Burbank, Red McClure and Teton tubers were inoculated, in all combinations, with inocula from ring-rot-infected tubers of the Bliss Triumph, Red McClure and Teton varieties. Resistant seedlings and susceptible varieties were also each used collectively as sources of inocula. Under the conditions of the experiment, the percentage of ring-rot infection and the severity of infection caused by inocula from susceptible varieties was equal to, if not greater than, that caused by inocula from resistant varieties. Plant symptoms developed much earlier in the Bliss Triumph variety than in the Burbank, Red McClure and Teton varieties. Symptoms of ring-rot were slight to absent in the latter variety. In this experiment, the conditions at the Laramie Station (7165 feet elevation) were better adapter for ring-rot symptoms in the plants than at the Torrington Station (4104 feet elevation), although the plant symptoms took a few days longer to become visible at the higher altitude than at the lower one. Microscopic examination of the slides showed that, as an average of all inoculations, far more bacteria were present in the Red McClure, Bliss Triumph and Burbank varieties than were present in the Teton variety. Furthermore, as sources of inocula, the Bliss Triumph tubers produced, on the average, relatively more bacteria in the stems of other varieties tested than either the Red McClure or Teton variety. The results of these experiments show that ring rot bacteria infecting the Teton variety and ring rot-resistant seedlings were not more pathogenic than those carried by susceptible varieties, such as the Bliss Triumph.