Fungicide seed treatments of sainfoin control seed‐borne and root‐invading fungi

Abstract

Laboratory and glasshouse experiments were carried out to study the effects of seed treatments with thiophanate‐methyl or a sulphuric acid copper+zinc complex at the rate of 3 g active ingredient (a.i)/kg seeds on seed‐borne and root‐invading fungi, and on growth of sainfoin (Onobrychis viciifolia Scop.) in China. Thiophanate‐methyl was more effective than the sulphuric acid copper+zinc complex in reducing fungal infection. This treatment eliminated Fusarium oxysporum Schlecht. and Cladosporium herbarum (Pers.) Link from seeds, and reduced the total percentage of root segments yielding fungal colonies and the percentage frequencies of isolation of F. oxysporum, F. solani (Mart.) Sacc, and other species of Fusarium. This fungicide did not control Alternaria alternata (Fr.) Keissl. on the seeds or in the roots of sainfoin seedlings growing in pots containing field soil. In invasiveness tests using sainfoin seedlings grown on water agar, 25 of the 35 fungal isolates, including isolates of common seed‐borne and soil‐borne fungi, formed necrotic lesions containing fungal hyphae on roots. In pathogenicity tests in pots of sterilised field soil amended with fungal inoculum, fungi isolated from roots were found more virulent than those from seeds. Among them, F. oxysporum and Drechslera tetramera (Mckinney) Subram and Jain were the most virulent species. Alt. alternata, Aspergillus flavus Link, C. herbarum, F. culmorum (W. G. Smith) Sacc, F. solani, and Penicillium sp. showed lesser pathogenic effects on seedling growth. The effects of fungicide seed treatments on plant growth varied with different field soils. Thiophanate‐methyl was superior to the sulphuric acid copper+ zinc complex, increasing shoot and root dry weights up to 55.5 and 60.0% respectively in some soils tested. These experiments demonstrated that thiophanate‐methyl seed treatment effectively controlled some pathogenic fungi both on the seeds and in soils and enhanced growth of young sainfoin plants.

Keywords:

• Onobrychis viciifolia
• root‐invading fungi
• sainfoin
• seed treatments
• seed‐borne fungi
• seedling growth
• thiophanate‐methyl