Abstract:
Powdery mildew caused by Blumeria graminis f.sp. tritici is an annual disease on wheat in all
regions where the crop is grown. This investigation studied the dynamics of development and
propagation of the cause agent of powdery mildew in wheat in the region of North-East Bulgaria
during 2013 - 2015. Monogenic lines and lines with two or three genes for resistance to the
pathogen were used in the investigation. The attacking rate was read on the 10th day as 0-100 %,
and the type of infection - from 0 to 4. The relative attacking rate was calculated on the basis of
the obtained results according to the highly susceptible line Mich. Amber x Cc 8 (Pm 6) used as
a standard in this case. The development and propagation of powdery mildew is strongly limited
under temperatures exceeding 25.c, rainfalls above 4 mm, and also by the efficiency of the
genes for resistance to the pathogen. During the investigated period, variable virulence was
formed in the powdery mildew population; it varied by its quantity and distribution over the
individual years. The highest attacking rate was observed in the populations with virulence V- 1,
V- 2, V- 2+, V- 4b, V- 5, V- 6, V- 7, V- 8, V- 17, V- 2+8, V- Mli . The populations with
virulence V- 3a, V- 3c, V- 2+4b+6, V-Mld had low rate of propagation. The populations with
virulence V- 3b, V-4a, V- 1+2+9, V- 2+6, V- 5+6 occupied intermediate position by their
attacking rate. |
