31 Resistance of tomato lines to races of Xanthomonas vesicatoria Sotirova, V . 1 . and Bogatsevska,   N . 2 1 Institute of Genetics, BAS, 1113 Sofia, Bulgaria 2 Institute of Plant Protection, 2230 Kostinbrod, Bulgaria Bacterial spot of tomato caused by Xanthomonas vesicatoria (Xv) is one of the most important diseases in regions of high temperature and frequent rainfalls (Pohronezny and Volin, 1983) . Three pathotypes (XvT), (XvP) and ( XvPT) were distinguished (Riche and Ditapongpich, 1991) . Tomato (XvT) and pepper - tomato (XvPT) pathotypes were established in Bulgaria (Bogatsevska and Sotirova, 1992) . Strains of XvT pathotype are further divided into a number of races (Wang et al . , 1990) . Three races of Xv are known (Bouzar et al . , 1994) . Race T1 and race T3 were identified in Bulgaria (Bogatsevska and Sotirova, 2000) . Race T3 has predominated during recent years . Antibacterial compounds and mixtures containing cooper are not efficient during the period of hot and rainy weather (Gitaitis et al . ) . The development of resistant lines or varieties is the most promising method for control of disease on plants . Breeding tomato lines obtained by hybridization with wild tomato species were tested for resistance to race T1 and T3 of Xv . The XvT – race T1 strain Xvt – 12 isolate from the root of Amaranthus caudatus and race T3 strain 19/1 isolate from tomato were used for inoculation . The bacteria was grown on potato sacharose agar media for 36 - 48h . The inoculum was prepared by removing the bacteria from the plate, suspending it in water and diluting to 10 8 cfu/concentration . Tomato plants at 5 - 6 true leaf stage were inoculated by vacuum infiltration method (Bogatsevska, 1988) . The infiltrated plants were grown in greenhouse at temperature 22 - 25 o C . Each plant was calculated by the 5 - range scale of Sotirova and Beleva (1975): 0 - lack of symptoms; 1 – 1 to 10 spots per plant; 2 – 11 to 20 spots per plant; 3 – 21 to 50 spots per plant; 4 – more than 50 spots per plant . The average degree of disease (x) was calculated . 30 – 50 plants of each line were tested for resistance to race T1 and T3, respectively . A series of lines were tested for resistance to race T1