Uredospore density of Puccinia triticina races on infection efficiency in wheat

Efeito da densidade de uredosporos de raças de Puccinia triticina na eficiência da infecção, em trigo

ABSTRACT

Wheat leaf rust caused by the fungus Puccinia triticina may lead to damage of up to 62%. This study aimed to test the effect of different uredospore concentrations on the infectious process of four physiological races. The races MFJ-MN, MFT-MT 4002 S, TPT-HT and TDP-HT were inoculated, when the first leaf was expanded in the seedling stage, on cultivars Ônix, Abalone, Morocco and Quartzo, respectively. The tested concentrations were 0.0; 5 x 10³; 10 x 10³; 20 x 10³ and 40 x 10³ uredospores/mL mineral oil (Soltrol). After inoculation, seedlings were kept in a growth chamber at 20°C ± 2, near 100% humidity, in the dark, for 20 hours. Fifteen days after inoculation, the density of uredia/leaf was evaluated. The concentration of 40 x 10³ uredospores/mL resulted in a disease intensity that allows safe differentiation between susceptible and resistant cultivars in the seedling stage, without causing leaf senescence due to high uredinium density.

Keywords
Inoculum concentration; leaf rust; physiologic races; cultivar reaction; Triticum aestivum