Incidência de Mancha Púrpura (Alternaria porri Ell. Cif.) em cultivares e híbridos de cebola (Allium cepa L.), em Manaus, Am. ()

Abstract

Susceptibility to Alternaria porri was evaluated in onion (Allium cepa L.) hybrids and cultivars in Manaus, AM. The desease occurs naturally and observations were made at the end of the vegetative cycle. Plants were grouped in classes as follows depending on % infection: I (0-10%); II (10-30%); III (30-50%); IV (50-70%) and V (> 70%). The (Px-76) hybrid was the only one that had plants in the classe I. Most plants (39,03-18,17%) of Barreiro Roxa, Pira Lopes, Pira Tropical, Pira Rosa and Pira Ouro cultivars and the (Px-25) hybrid showed 30-50% infection. The (Px-31) hybrid was the most suscetible, with 50% of the plants being more than 70% infected.