Influence of temperature on virulence of race 3 strains of Pseudomonas solanacearum.
Since bacterial wilt caused by this race can be a severe problem at high elevations in Colombia and Peru where relatively low mean temps. predominate, and since race 3 exists within wide geographical areas, the possible existence of low-temp. specific strs. was investigated. Russet Burbank potato plants were stem-inoculated with 8 race 3 strs. and maintained in growth chambers at 16, 20, 24 and 28 deg C for 15 days. At the lowest temp. only 1 str. (S206) caused considerable wilting; S206 was more virulent than the other 7 strs. at both 16 and 20 deg . At 28 deg , however, no differences in virulence could be detected; all strs. caused complete wilting by 15 days. These results were confirmed in a second test in which 10 strs. were used, 5 of race 1 and 5 of race 3. Only 2 race 3 strs. (S206 and 257) caused wilting at lower temps; at 28 deg all strs. were equally virulent. Differences in virulence were not correlated with growth rates of the strs. in liquid culture at 16 deg ; some grew at rates similar to those of S206 and 257 in vitro, but did not cause symptoms in vivo at this temp.