Bacterial speck of tomato was detected in Bulgaria for the first time in 1974. Lawton and Mac Neill (1986) reported the existence of two races (0 and 1) in Canada. As part of a breeding program for resistant tomato varieties, we carried out an investigation on Bulgarian races of P. syringae pv. tomato.
During the period 1985 to 1987 we collected infected leaves and prepared 208 pure cultures from all over the country (141 of tomatoes and 67 of different weeds). We used two differential varieties - Ottawa 778 and ONT 7710 - for distinguishing between the races. The plants were inoculated after the vacuum infiltration method at first-true leaf stage with suspension of 36 hours old bacterial cultures. The concentration of the suspension was adjusted to 10^4 cfu/ml. Infiltrated plants were planted in a greenhouse and evaluated after five days.
The results showed that 205 isolates belong to the most common race 0 and only 3 - to race 1 (Table 1). The later was detected in 1987. The wide distribution of race 0 is determined by the growing of susceptible tomato varieties in Bulgaria up to now. The presence of race 1 imposes an investigation into new sources of resistance since there are not any reports on resistance to this race in literature till now.
Table 1. Test-varieties response to different isolates of Pseudomonas syringae pv. tomato (Okabe) Joung et al.
______________________________________________________________
Test-varieties Numbers of isolates with reaction
205 3
______________________________________________________________
Ottawa 78 S S
Ontario 7710 R S
Race O 1
______________________________________________________________
Literature Cited:Lawton, M. B. Mac Neill. 1986. Can. J. Plant Pathol. 8, 85-87.