Fungi associated with onion (Allium cepa L.) fields in southern Puerto Rico

Abstract

A survey was conducted in experimental and commercial onion (Allium cepa L.) fields in the southern region of Puerto Rico to isolate and identify fungi associated with this crop. Fungi were isolated from air, soil, and tissue from leaves and bulbs that showed typical disease symptoms. Commercial seeds from three onion cultivars commonly used in Puerto Rico were examined. Overall, Aspergillus niger was the fungus most frequently isolated from soil, bulbs and seeds. Fusarium spp. and Penicillium spp. were frequently isolated from air; A. niger, Fusarium and Cladosporium, from soil; and A. niger, Penicillium and Sclerotium rolfsii, from bulbs. In onion foliage, Alternaria was the most common genus, followed by Stemphylium and Nigrospora. In commercial onion seeds, A. niger and Rhizopus in combination were the most frequent.