Jan. 2. I920 Treatment of Cereal Seeds by Dry Heat 381 



exposures gave smut-free plants, but the 30-minute treatment greatly- 

 reduced the percentage of germination. 



Naumov (21, p. 149-162, 17^), in 1916, after having obtained negative 

 results from all known seed treatments in attempts to control wheat 

 scab (Gibberella sauhinetii (Mont.) Sacc. and Fusarium spp.), reports that 

 he was able to kill the infections on the seeds of cereals by dry heat. 

 Wheat, barley, and oats were subjected to 60° C. and rye to 65° C. for 

 periods ranging from 24 hours to 3 days. This treatment, according to 

 Naumov, killed the fungus mycelium present in the interior of the 

 kernels or at least weajcened it greatly. 



EXPERIMENTS 



The writers first attempted to duplicate Naumov's treatments, and 

 found his results difficult to verify. Wheat and barley thus treated 

 retained their viability, but so did the fungi Gibberella saubineiii and 

 the Fusarium, Helminthosporium, and Alternaria species infecting the 

 kernels of these grains. 



Following this, higher temperatures and longer exposures were tested 

 with rather surprising results. Some wheat and barley kernels remained 

 viable even after an exposure to 100° to 110° C. for as long as 45 

 hours. It was soon found possible by somewhat reducing this time to 

 lessen the injury to the seed and yet kill the most persistent parasites. 

 The barley used in these earlier experiments was Chevalier, a 2-row 

 variety, abundantly infected with Helminthosporium sativum, P. K. B. 

 and also to some extent with Gibberella saubineiii. The kernels most 

 badly infected with H. sativum are readily detected by the dark brown 

 germ ends; hence, such kernels were selected for the experiments. 

 This fungus has an added advantage for experimentation in that it sporu- 

 lates freely on culture media and can be identified readily. Furthermore, 

 H. sativum in the seed is more difficult to kill by the ordinary methods 

 of seed disinfection than most other parasites known to the writers. On 

 account of this resistance to seed treatments and because it is easily 

 identified, H. sativum was chosen as the main index of efficiency of the 

 dry-heat treatments tried. The wheat used in the earlier trials was a 

 durum wheat, Kubanka (South Dakota 75), which was infected with 

 Gibberella, Fusarium, Helminthosporium, and Alternaria.^ 



With the exception of one series these experiments were all made in 

 a gas-heated sterilizing oven. While it required considerable attention 

 throughout the duration of the treatments to keep the temperatures 

 reasonably constant, this was accomplished by careful watching and the 

 regulation of gas supply and ventilation as necessary. 



' This was kindly furnished by Prof. Manley Cbamplin, o( the South Dakota Agricultural Experiment 

 Station, Brookings, S. Dak. 



