Pathotype diversity of Uromyces appendiculatus in Northeastern Bulgaria

Abstract

Bean rust caused by Uromyces appendiculatus (Pers.: Pers.) Unger. is one of the most devastating fungal diseases in common beans. For the plains of Bulgaria, the disease has a sporadic spread but occurs annually in The Rhodope mountains. To determine the pathotype diversity in Northeastern Bulgaria, seventeen single uredinium isolates (SUIs) were obtained from a naturally occurring pathogen population. The virulent phenotype of the isolates to the differential set referred them to 16 pathotypes of four races. The pathotypes of race 20-16 had the highest frequency of isolation (56.3%), followed by the pathotypes of race 20-18 (31.2%) and the pathotypes of races 20-0 and 20-2 (6.3%). One pathotype was referred to the Andean-specific group of the pathogen and 15 pathotypes were referred to the non-specific group of U. appendiculatus. All pathotypes had a completely different virulent/avirulent phenotype compared to those previously described in Bulgaria. This investigation is the first report for the distribution of pathotypes of races 20-16 and 20-18 in the country. The high pathotype diversity of U. appendiculatus in Bulgaria is due to genetic recombination during the sexual process which occurs in The Rhodope mountains, or to mutations in the pathogen population as a result of breeding pressure of the new varieties grown in the country.

Keywords

• common bean
• pathotype diversity
• phaseolus vulgaris
• rust
• uromyces appendiculatus