Monitoring on the Pathogen Population of P. triticina in Bulgaria during 2013-2014

Abstract
The population studies on the cause agents of the diseases in agricultural crops are an indispensable stage in the development of a scientifically-coordinated strategy in the breeding for resistance. This investigation follows the changes in the population structure of P. triticina during harvest years 2013-2014. The analysis on the population structure was carried out according to the methodology adopted at the Plant Pathology Laboratory of Dobrudzha Agricultural Institute – General Toshevo, Bulgaria. We developed 139 monoracial isolates from 47 samples. A total of 59 pathotypes were identified (27 in 2013 and 32 in 2014), 5 of the pathotypes (02762, 12722, 12762, 12763 and 52762) being determined during the two years of the investigation. Twenty-five new pathotypes were identified, which were not detected during 2000-2012. The distribution of the pathotypes in the individual agro ecological zones was uneven. Three of the pathotypes were dominant: 12762, 52762 and 53763.The genes for resistance to this pathogen demonstrated variable efficiency. The strong genes Lr 9 and Lr 19 were absolutely efficient in 2013, but in 2014 pathotypes were identified, which overcame their resistance. During the first years of the study, genes Lr 2c, Lr 9, Lr 19, Lr 22A, Lr 22B, Lr 25, Lr 41 and Lr 45 reacted as absolutely efficient, while during the second year absolute efficiency was demonstrated by genes Lr 22A, Lr 22B and Lr 25. Good was the efficiency of genes Lr 2a, Lr 2b, Lr 3ka, Lr 24, Lr 42, Lr 44, Lr 45, Lr 46 and Lr 47. Low efficiency was found in genes Lr 1, Lr3, Lr 10, Lr 11, Lr 15, Lr 16, Lr 17, Lr 18, Lr 20, Lr 21, Lr 23, Lr 26, Lr 36, Lr 37, Lr 39, Lr 48, Lr 51 и Lr 52. Absolutely inefficient were genes Lr 30, Lr 38 and Lr 60.