Phosphites improve tolerance to gray mold and induce defense mechanisms in the ?Hayward? kiwifruit

ALEJANDRA YOMMI; FELDMAN M.L.; OLIVIERI FP; GUZZO MC; PATRICIA A. SUAREZ; QUILLEHAUQUY V; ANDREU AB

Dujiangyan

Simposio; VIII International Symposium on Kiwifruit; 2014

Gray mold, caused by Botrytis cinerea L (B.c.), is the most important postharvest disease on kiwifruit. As preharvest fungicides not effectively protect the fruit against pathogens, the search for alternative substances has increased. Among them, the use of phosphites (Phi), low-toxicity compounds, has emerged. Previous reports showed that Phi acts both increasing plant defense responses and crop yield. The objectives of this work were to assess the effects of potassium phosphite (KPhi) on gray mold incidence on kiwifruit and on the molecular defense responses to B.c infection. In a first season (2012), weekly foliar applications of 0.3% (v/v) of KPhi or water during fruit growth (FG) were done in a commercial mature orchard of 'Hayward' kiwifruit. After that, preharvest treated and control fruits were treated with 1% KPhi or water in postharvest. In a second season, we study the effect of the moment of application of 0.3% KPhi, including: blooming (BL), FG and both combined (BL+FG). In both seasons, the incidence of gray mold was analyzed. KPhi treatment diminished the disease incidence in the first season (KPhi=30.6%; Control=61.0). Excepting for BL+FG treatment that did not differ with the control, KPhi statistically diminished the disease incidence in the second season (BL=48.7%, FG=57.8%, BL+FG=68.9, Control=70.7%). Activity of peroxidases, and glucanase and chitinase expression, were increased when KPhi was applied, and in some cases was higher in both treated and Bc inoculated ones. These results would indicate that Phi increased defense responses in kiwifruit. More studies are necessary to understand all the molecular changes involved in these responses.