Effect of alternative strategies for the disinfection of tomato seed infected with bacterial canker (Clavibacter michiganensis subsp. michiganensis)

Abstract

Currently there is a lack of effective seed treatments for bacterial pathogens, with Cu-based compounds (the only chemical treatments permitted under organic farming standards) only providing partial control. The aim of this study was to quantify the effect of alternative treatments for the control of bacterial canker (Clavibacter michiganensis subsp. michiganensis), a major seed-borne bacterial disease in tomato. Treatments assessed were acidified nitrite (a treatment previously shown to control the seed-borne fungal disease Didymella lycopersici), antagonistic strains of Bacillus spp. and compost extracts, which were not previously evaluated as treatments for seed-borne diseases. Efficacy of treatments was determined in a seed disinfection assay. Ten-minute immersion of seed in 300 mmol l −1 acidified nitrite resulted in 98% being pathogen free. Copper hydroxide, certain strains of Bacillus spp. and all compost extracts resulted in 100% pathogen free seed.

Plant disease management in organic farming systems

“…Chemical seed treatment after extraction is not allowed either. There are three main seed treatment methods for organically produced seeds: (1) physical methods; (2) treatment with plant extracts; (3) seed coating with biological control agents or their extracts . As physical methods, hot water or steam treatment, followed by drying, can be used in organic seed production .…”

“…As physical methods, hot water or steam treatment, followed by drying, can be used in organic seed production . Various plant extracts (ethereal oils), organic acids and biological control agents have been tested for the control of seed‐borne pathogens . An emulsion of thyme oil and a solution of ascorbic acid were most promising, although these can be phytotoxic at too high concentrations and have not been registered yet for organic production .…”

“…A complex microbial community as found in organically managed soils and on plant surfaces generally contains a variety of general antagonists and parasitic microorganisms such as Pythium oligandrum or Trichoderma species that suppress pathogenic fungi. Organic farmers sometimes try to increase microbial populations and diversity on plant surfaces by applying compost extracts, also called compost teas, especially in the United States . The effects are variable, depending on the starting material, the composting and fermentation procedures and period, the water ratio, added nutrients such as molasses, temperature and pH .…”

“…There are three main seed treatment methods for organically produced seeds: (1) physical methods; (2) treatment with plant extracts; (3) seed coating with biological control agents or their extracts. 64 -66 As physical methods, hot water or steam treatment, followed by drying, can be used in organic seed production. 65 Various plant extracts (ethereal oils), organic acids and biological control agents have been tested for the control of seed-borne pathogens.…”

Keefektifan Perlakuan Fisik dan Minyak Atsiri untuk Mengeliminasi Bakteri Clavibacter michiganensis subsp. michiganensis pada Benih Tomat

“…michiganensis secara kimiawi menggunakan tembaga hidroksida yang diaplikasikan dengan mankozeb dan antibiotik streptomisin dilaporkan oleh Kasselaki et al (2011) dan Werner et al (2012). Akan tetapi, penggunaan antibiotik dapat menimbulkan resistensi pada patogen dan pencemaran lingkungan.…”