Characterization of Pseudomonas syringae pv. phaseolicola Races in North-Eastern Bulgaria

I. KIRYAKOV
Dobroudja Agricultural Institute, BG-9520 General Toshevo, Bulgaria

Abstract

KIRYAKOV, I., 2001. Characterization of Pseudomonas syringae pv. phaseolicola races in North-Eastern Bulgaria. Bulg. J. Agric. Sci., 7: 313-318

Halo blight caused by the bacterium Pseudomonas syringae pv. phaseolicola is one of the three bacterioses on bean (Phaseolus vulgaris L.) distributed in Bulgaria. The use of resistant cultivars is the most efficient means for control of the disease. Unfortunately the resistance of the cultivars is not always stable due to the occurrence of new more virulent strains of the pathogen. This paper presents data on the race variability of P. s. pv. phaseolicola in North-Eastern Bulgaria. The physiological specialization of 42 P. s. pv. phaseolicola isolates was determined on the basis of the disease reaction of 8 bean cultivars and lines included in a standard differential set after infiltration of the bacterial suspension (108 cfu/ml) at primary leaf stage. The response of six released dry bean cultivars and one candidate cultivar to the established pathogen races was studied. Five races of P. s. pv. phaseolicola were identified in North-Eastern Bulgaria – races 1, 2, 6, 7 and 9. Four of them (races 2, 6, 7 and 9) were isolated from green bean accessions grown in small farm gardens, and two of the races (6 and 1) were isolated from domestic and introduced bean accessions grown at DAI – General Toshevo. The cultivars Dobroudjanka 2, Dobroudjanski 7, Astor, Vulkan, Abritus and the candidate cultivar Dobroudjansky ran are highly to moderately resistant to the studied races. Cultivar Loudogorie was susceptible to races 1 and 6 and highly to moderately resistant to the other races. The results obtained showed considerable variation in the virulence of the P. s. pv. phaseolicola strains distributed in North-Eastern Bulgaria, especially having in mind the resistance of the commonly produced dry bean cultivars.

Key words: halo blight, P. s. pv. phaseolicola, race, Ph. vulgaris, resistance