Mycoflora of Rice (Oryza Sativa L.) Seed in New Zealand

Abstract

The seed-borne fungal flora of twenty stored and eleven freshly harvested samples of New Zealand-grown and overseas-grown rice seed was studied. Five methods were employed for detecting the organisms present; the Ulster, Modified Ulster, Surface Sterilization, Filter Paper and Heat Treatment Methods. Fifty-four fungi belonging to thirty genera were identified. Those recorded from New Zealand-grown rice seed for the first time include: Alternaria alternata, Curvularia lunata (Curvularia state of Cochliobolus lunatus), Curvularia trifolii, Drechslera australiensis, D. hawaiiensis,D. bicolor (Drechslera state of Cochliobolus bicolor), Epicoccum purpurascens, Nigrospora oryzae (Nigrospora state of Khuskia oryzae), Pithomyces chartarum, Aureobasidium pullulans, Pestalotia oryzae, Peyronellaea sp., Stemphylium botryosum (Stemphylium state of Pleospora herbarium), Ulocladium botrytis, six species of Fusarium, i.e. F. arthrosporioides, F. culmorum, F. flocciferum. F. lateritum, F. oxysporum, F oxysporum var. redolens. Two of the most serious rice pathogens, i.e. Drechslera oryzae (Drechslera state of Cochliobolus miyabeanus) and Alternaria padwickii, and Fusarium semitectum and sporotrichoides were isolated from overseas-grown, but not New Zealand-grown rice seed. Illustrations and descriptive notes of these fungi are given. Pathogenecity tests were carried out for a selected number. The fine detail of some isolates was studied with the scanning electron microscope. The Filter Paper Method was found to be the most efficient method for detecting rice seed-borne fungi. Three out of ten fungicides tested, i.e. Rhizoctol, Rhizoctol Combi and .Busan 72 when applied as seed dressings gave efficient control of seed-borne fungi.