Abstract

LADO, Joanna; LUQUE, Eleana; BLANCO, Oribe  and  PEREZ FAGGIANI, Elena. Evaluation of alternatives for Penicillium digitatum imazalil resistant strains postharvest management. Agrociencia Uruguay [online]. 2011, vol.15, n.1, pp.55-63. ISSN 1510-0839.

The control of Green mold caused by Penicillium digitatum in Uruguayan packinghouses is based in imazalil (IMZ) application. As a result, resistant strains appeared. The aim of this work was to evaluate different alternatives for postharvest control of IMZ resistant (1.0 mg l-1 in vitro) P. digitatum strains. Valencia and Ellendale fruit were inoculated with P. digitatum S22 (IMZ sensitive) and R20 (IMZ resistant) strains.  Afterwards, they were treated by a 15 s immersion in IMZ, pyrimethanil (PYR) or fludioxonil (FLU) alone or combined with salts: sodium bicarbonate (BCS), sodium carbonate (CS) or potassium sorbate (SP). After 15 days of storage at 20 ± 2  ºC pathogen incidence was registered. For Ellendale, IMZ was the best fungicide for sensitive strain management, achieving 100% control with 500 mg l-1. Although disease incidence was lower than 25% with 500 µL l-1 PYR or FLU application, control efficacy was lower than for IMZ treatment. For resistant strain PYRand FLU were as effective as IMZ (1500 mg l^-1), with 80% of healthy fruit. BCS applied at 1, 2 or 3% reduced pathogen incidence, being significantly superior in mixture with IMZ 500 mg l^-1. For Valencia oranges an incidence reduction higher than 90% was obtained by  IMZ 1500 mg l^-1  and  IMZ + PYR 750 µL l^-1. These alternatives reveal that is possible to develop anti-resistance strategies for P. digitatum IMZ resistant strains management.

Keywords : pyrimethanil; fludioxonil; sodium carbonate; sodium bicarbonate; potassium sorbate.

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