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New Zealand Plant Protection 63 (2010): 277

Dry hot air reduces seed-borne pathogens of carrot seeds

L-H. Cheah, J. Townshend and D.I. Hedderley

ABSTRACT

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 (70C or 75C) 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 20C). Temperature treatment at 75C for 20 and 30 min killed almost all Alternaria. This pathogen was significantly less likely to occur after 75C than 70C (P=0.038). For Fusarium there was no significant difference between treatments. Treatment at 75C reduced Xanthomonas on the seeds significantly more than 70C (P=0.031). Higher temperatures and longer treatment both tended to reduce germination, with the 75C for 30 min treatment having the least germination. Seedling weight tended to be lower after 75C than 70C, but length of treatment had minimal effect. It is concluded that 70C 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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