A Study of the Seed-Borne Fungal Flora of New Zealand Seed Oats, with Particular Reference to the Pathogens

Abstract

The seed-borne fungal flora of fifty-two samples of New Zealand seed oats was studied. Five methods were employed for detecting the fungi present, the Ulster, Filter Paper, Heat Treatment (one hour at 100°C), Surface Sterilization (10 minutes in a solution of 2% available chlorine) and Seed Washing Methods. Forty-nine fungi belonging to thirty-seven genera were identified. Alternaria tenuis auct., Cladosporium spp. and Epicoccum nigrum (Link) Schol-Schwarz, all considered to be non-pathogens, were the most frequently isolated. Forty-one samples were infected with the pathogen Helminthosporium avenae Eidam, and twenty-four samples with Fusarium spp., mostly F. poae (Peck) Wollenweber. Algerian oats were found to be more heavily infected with H. avenae than Onward oats. The percentage of seeds shown by plate methods to be contaminated with Penicillium spp. increased with the age of the seed while the percentage of A. tenuis decreased. Of the culture plate methods studied, the Ulster and Heat Treatment methods were the most efficient for detecting H. avenae; the Heat Treatment method was preferred because it allowed easier counting of colonies. Thirteen fungi are described: five species of Helminthosporium: H. avenae, H. sativum Pamm., King & Bakke, H. cyclops Drechs., H. biforme Mason & Hughes, and H. tetramera McKinney; four of Fusarium, F. avenaceum (Fr.) Sacc., F. culmorum (W. G. Sm.) Sacc., F. poae and Fusarium sp.; and one each of Cephalosporium, Pellicularia, Pestalotia and Phoma.