Adjuvant concentrations and uredospore densities on Phakopsora pachyrhizi infection efficiency in soybean

Abstract

Experiments were carried out in a growth chamber to evaluate the effect of spreader and uredospore concentrations on the efficiency of infection by Phakopsora pachyrhizi, the causal agent of Asian soybean rust. CD 214 RR soybean cultivar was inoculated with the following polyoxyethylene sorbitane monolaurate concentrations: 0, 30, 60, 120, 240, 480 and 960 µL.L-1 water, as well as a fixed uredospore concentration of 2 x 10(4) spores.mL-1. In a second phase, the inoculum concentrations of 0, 5 x 10³, 1 x 10(4), 2 x 10(4), 4 x 10(4), 8 x 10(4) and 16 x 10(4) uredospores.mL-1 were evaluated, and the spreader concentration of 240 µL.L-1, selected in the previous experiment, was fixed. The spreader concentration of 240 µL.L-1 can be used in artificial inoculation studies, as well as up to 4 x 10(4) uredospores.mL-1. In this work, there was a correlation between uredia and lesion density. Thus, the use of lesion density is recommended to assess disease intensity for its accuracy and less time consuming. There was also a positive correlation between uredia and lesion density.

Uredospore density of Puccinia triticina races on infection efficiency in wheat

“…Although working with other pathosystems, Carlini (5) and Zanatta & Reis (11) also observed that the highest inoculum concentration resulted in a corresponding increase in the disease intensity, also confirmed in our study.…”

“…Moreover, inoculation with low concentrations generates individualized uredia, facilitating their quantification and extending the green leaf area duration. Zanatta & Reis (11) used the concentration of 40 x 10 3 spores/mL to maintain the P. pachyrhizi inoculum as the optimal concentration.…”

Detached wheat leaf assay for assessing the sensitivity of Puccinia triticina races to fungicides

“…Adjuvant (Tween 20) was added at 120 μL/L to the suspension to optimize leaf cover and avoid areas without deposition. In the control treatment, only distilled water and adjuvant was sprayed on both plants and Petri dishes (15).…”