EN

Abstract

Common bunt of wheat is one of the most serious diseases which caused heavy losses to wheat crop especially when seed of susceptible varieties were sown without treated with fungicides. The study was conducted to determine the genetic variability and pathogenicity of two Tilletia species Tilletia tritici and T. leavis through analyses the reaction characters of pathogenic isolates with differential varieties. Spike showing infections of common bunt were collected from the major wheat growing areas of Iraq during 2012/2013 cropping season. Based on the higher percentage of teliospores germination, 18 isolates of common bunt were selected and used for contamination the seed of differential varieties at faculty of agricultural sciences fields in Sulimania. Results of study revealed the existence of large genetic variation between T. tritici isolates representing different ecological areas. Among the 18 selected isolates, ten were showing similarity with the already reported world races,T1,(T1, L1, L2), T2 ,T4 ,T9, T11, T13, T12, T18, T20) while the rest 8 isolates could be new races and to best of our knowledge not recorded previously in any part of the world. It has been found that the resistance genes Bt2, Bt6, Bt14 and Bt15 were not effective against most of pathogenic isolates, while Bt1 was found non effective against 5 isolates, Bt4, and Bt8 were non-effective against 4 isolates, Bt3 and Bt5 were ineffective against 3 isolates only. All the isolates were found unable to overcome the resistance genes Bt11 and Bt12, where 2 isolates were found able to overcome the resistance genes Bt7, Bt9, Bt10 and Bt13.