TITLE:
Biological Methodologies on SDHI Fungicides to Assess Reductions of Sensitivity and Activity on Venturia inaequalis and Cross-Resistance Tests
AUTHORS:
R. Fiaccadori, G. Battistini
KEYWORDS:
Venturia inaequalis, SDHI, Fungicides, Scab Control, Sensitivity, Methodology
JOURNAL NAME:
American Journal of Plant Sciences,
Vol.12 No.7,
July
29,
2021
ABSTRACT: Biological methodologies (in vitro and in vivo)
were tested on Venturia inaequalis to
assay sensitivity of populations treated with the SDHI penthiopyrad,
fluxapyroxad and fluopyram that showed a field poor control in an experimental
Centre. In comparison, sensible populations were tested. In vitro trials, the poorly controlled
populations presented moderate increases of EC50 and RF values in
all three years in which tests were carried out. The in vivo trials in glasshouse showed that the activity of SDHI
fungicides on field poorly controlled populations was highly reduced. These
populations can be defined as “resistant” as the high loss of sensitivity and
activity were repeatedly assessed in field and glasshouse. Trials showed that
these reductions were manifested by curative applications and not by preventive
ones, as already ascertained for V.
inaequalis populations resistant to AP and DMI fungicides. The cross-resistance of resistant populations to
the three SDHIs was highly positive among them. In bibliography, there are only
researches of cross-resistance among SDHIs starting from isolates resistant to
boscalid, with results of different sensitivities and cross-resistance. These
results with populations of V. inaequalis resistant to the three SDHI offer practical evaluations in cross-resistance.