PHYSIOLOGICAL SPECIALIZATION OF WHEAT LEAF RUST (Puccinia triticina ERIKS.) IN BULGARIA

Leaf rust on wheat caused by Puccinia triticina Eriks. is a disease widespread in all parts of the world where wheat is a main cereal crop. The race, pathotype and genetic variability of the pathogen's population in Bulgaria were investigated. The virulence of the pathogen population was studied on Thatcher near isogenic of 221 isolates were analyzed. Seventy-one phenotypically different pathotypes were identified. Pathotypes 63562, 63573 and 63762 had the highest frequency of occurrence. For the first time in this population 25 entirely new pathotypes were identified. The genetic variability was represented by 86 genetic formulae for virulence. The most common combination was 1, 9, 15, 19, 24, 28 / 2a, 2b, 2c, 3, 11, 17, 21, 23, 26 (37.9%). The genes for resistance demonstrated variable efficiency. During this period the immunity was conferred by Lr47 and Lr50 demonstrated very good to high efficiency. During the investigated period, pathotypes were found which were overcoming the resistance of the two strong genes Lr9 and Lr19.