TO June, 1910.] Testing Potato Varieties for IrisJi Blight. 



359 



V .. and subsequentlv kept moist in a bell-jar to see if the fungus developed. 

 While there was no trace of the disease in the treated lot, those untreated 

 ■de\-eloped the fungus freely. Not only so, but the treated tubers sprouted 

 more readily and better than the untreated, when kept in store and some 

 of them were planted in pots and invariably produced a healthy crop. 

 At a dry heat of 120 deg. to 122 deg. F. the mvcelium of the fungus is 

 destroyed inside the tissues of the p>otato, and there is no development of 

 the disease, unless infection occurs from outside sources. 



A supply of .seed potatoes of special sorts was obtained from Sutton 

 and Sons' agent in New Zealand, having been growai there from seed sent 

 ■out by the firm in England. They were forwarded to me in a strong box 

 and carefully examined before being planted in pots in my laboratory. 

 In one of the vaxieties (British Queen) the disease was detected and this 

 shows the necessity for treating with suspicion even the best guaranteed 

 samples. There were nine selected varieties altogether, viz., Sutton's 

 Abundance, Sutton's Superlative, British Queen, Windsor Castle, Ninety 

 Fold, S. S. Seedling. Early Regent, Supreme, and Discovery ; and speci- 

 mens of each were planted on loth November, 1909. 



Sutton's Abundance, Sutton's Superlative, and British Queen, were 

 subjected to a drv heat of 120 deg. F. for four hours, and the rest were 

 planted without any treatment. 



The results were taken on 31st March, and under the limitations in 

 which they were grown, the tubers produced were mostly small. The 

 growth was closelv watched. In twelve days Sutton's Abundance and 

 Supreme were above ground and in fifteen days all had appeared. The 

 two varieties which sprouted llrst took the lead from the start, and in 

 31 days, Sutton's Abundance was the best looking of the lot and Suprem.e 

 nearly as good. By the end of March the tops had all withered naturally, 

 and the results are shown in following table : — 



Owing to the restriction imposed bv Western Australia that potatoes 

 will not be accepted when grown within 50 miles of an infected area, I was 

 unable to carry out experiments on a larger scale and in the open field, 

 but the fact remains that potatoes can be submitted to a dry heat of 120 

 ■deg. F. for four hours and still grow luxuriantly, and that potatoes so 

 treated did not develop the Irish Blight. Some of the varieties, such as 

 Briti.sh Queen, in which the fungus of the Irish Blight was found, did 

 not develop the disease after treatment. 



Small quantities of potatoes can easily be submitted to drv heat and 

 kept at a constant temperature in the incubator, but arrangements could 

 be made for the treatment of large quantities, so as to insure the destruction 

 of the spawn of the fungus if it existed in the tuber. 



