Efficacy of Hot Water and Chlorine for Eradication of Cladosporium variabile, Stemphylium botryosum, and Verticillium dahliae from Spinach Seed

Lindsey J du Toit; Pablo Hernandez-Perez

doi:10.1094/PD-89-1305

Cladosporium variabile, Stemphylium botryosum, and Verticillium dahliae are seedborne and seed-transmitted pathogens of spinach. Spinach seed treatments in 1.2% NaOCl for 10 to 60 min, or hot water (40, 45, 50, 55, and 60°C) for 10 to 40 min, were evaluated for eradication of these fungi from seed. C. variabile and V. dahliae were largely eradicated by chlorine treatment for ≥ 10 min. Although chlorine treatment reduced the incidence of S. botryosum, this fungus was not eradicated after 60 min in chlorine. Seed germination was not affected adversely by chlorine treatment, even after 60 min. In contrast, germination was reduced significantly by hot water treatment at 50°C for ≥30 min or 55 or 60°C for ≥10 min. C. variabile was eradicated from seed treated in 40°C water for 10 min. V. dahliaewas eradicated from seed treated at 55°C for ≥30 min or 60 °C for ≥10 min. S. botryosum was eradicated from a lightly infected seed lot (5% incidence) by hot water treatment at 55 or 60 °C for ≥10 min, but could not be eradicated from two heavily infected lots (>65% incidence), even at 60°C for 40 min. Using precisely controlled parameters, chlorine or hot water seed treatments can be used to eradicate C. variabile and reduce the incidence of S. botryosum and V. dahliae in spinach seed without damaging germination. Cladosporium variabile, Stemphylium botryosum, and Verticillium dahliae are seedborne and seed-transmitted fungal pathogens of spinach. Spinach seed treatments in chlorine (1.2% NaOCl) for 10 to 60 min or in hot water (40, 45, 50, 55, and 60°C) for 10 to 40 min were evaluated for their potential to eradicate these fungi from spinach seed. C. variabile and V. dahliae were eradicated by chlorine treatment for as little as 10 min. Chlorine treatment reduced the incidence of S. botryosum, but this fungus was not eradicated even after 60 min in chlorine. Seed germination was not affected adversely by chlorine treatment. However, germination was reduced by hot water treatment at 50°C for 30 min or longer, or at 55 or 60°C for 10 min or longer. C. variabile was eradicated from seed treated at 40°C for only 10 min. V. dahliae was eradicated from seed treated at 55°C for at least 30 min or at 60°C for 10 min or longer. S. botryosum was eradicated from a lightly infected seed lot by hot water treatment at 55 or 60°C for 10 min or longer, but not from two heavily infected lots, even when heated to 60°C for 40 min. Using precisely controlled parameters, chlorine or hot water seed treatments can be used to eradicate C. variabile and reduce the incidence of S. botryosum and V. dahliae in spinach seed without damaging germination.

Efficacy of Hot Water and Chlorine for Eradication of Cladosporium variabile, Stemphylium botryosum, and Verticillium dahliae from Spinach Seed

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