New Zealand Plant Protection 63 (2010): 277
The effect of dry hot treatment of carrot seeds on seed-borne pathogens (Alternaria dauci, Fusarium solani and Xanthomonas sp.) and seed germination was investigated. Carrot seeds (no fungicide) were soaked in water for 1 min before being exposed to hot air (70°C or 75°C) for 10, 20 or 30 min and then plated on potato dextrose agar to assess pathogen growth. Treated seeds were sown in cell trays in a glasshouse to assess germination and weight of subsequent seedlings. All dry hot air treatments significantly (P<0.001) reduced the number of seeds bearing three pathogens compared with the control (air dried at 20°C). Temperature treatment at 75°C for 20 and 30 min killed almost all Alternaria. This pathogen was significantly less likely to occur after 75°C than 70°C (P=0.038). For Fusarium there was no significant difference between treatments. Treatment at 75°C reduced Xanthomonas on the seeds significantly more than 70°C (P=0.031). Higher temperatures and longer treatment both tended to reduce germination, with the 75°C for 30 min treatment having the least germination. Seedling weight tended to be lower after 75°C than 70°C, but length of treatment had minimal effect. It is concluded that 70°C for 10 or 20 min is the best treatment for reducing seed-borne pathogens without affecting the viability of carrot seeds.
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