52 BULLETIN 727, U. S. DEPARTMENT OP AGRICULTURE. 



In a total of more than 4,000 seeds tested no anthracnose was 

 found. From the 3,100 seeds tested in sterile soil no diseased seed- 

 lings developed. Where culture media were used the profuse devel- 

 opment of bacteria and fungi upon and around each seed proved 

 that the latter bore an abundant and varied surface flora. On 

 old seed the flora was less varied. The rapid development of these 

 forms rendered anthracnose isolation by cultural methods a matter 

 of great difficulty. 



To determine whether or not the methods employed above were 

 reliable, tests were made with seed previously dipped in a spore 

 suspension. The results of these tests warrant a more detailed 

 account. On March 13 about 500 seeds were immersed for 50 minutes 

 in a heavy suspension of spores of the anthracnose fungus and then 

 dried on filter paper. The next day 50 of these seeds were planted 

 in sterile moist sand in a damp chamber. The seedlings were sprayed 

 from time to time with sterile water. Sixteen days after planting, 

 one seedling, which had carried its seed coat up with the cotyledons, 

 showed an anthracnose lesion on the stem near the ground line and 

 another on a cotyledon. Owing to the stem lesion the seedling had 

 already fallen over, as in damping-off. On the stem lesion were numer- 

 ous sporulating acervuli. In 22 days after planting, three more 

 seedlings had damped-off with anthracnose and four others bore 

 lesions at the ground line. In 29 days after planting, 16 out of the 

 45 seedlings had succumbed to anthracnose. 



These results corroborate those secured by Carsner, 1 who obtained 

 damping-off of cucumber and muskmelon seedlings when seeds pre- 

 viously dipped in a spore suspension were planted in sterile soil. 

 Such results suggest that perhaps in the field the originally diseased 

 plant may damp-off and disappear, so that the first lesions dis- 

 covered are the result of spores splashed from this plant upon those 

 adjacent to it. 



To test the filter-paper culture method, 28 of these inoculated 

 seeds were planted in four sterile Petri dishes on filter paper mois- 

 tened with 2 per cent dextrose solution. Six days later, acervuli of 

 anthracnose were found on two seed coats, and by nine days one 

 more seed bore acervuli and its seedling was diseased. Two weeks 

 after planting, two more seedlings were diseased. Mold and bacte- 

 rial growth was as usual abundant on these seeds. The results of 

 these and further tests with these seeds are presented in Table VI. 



While it is evident that diseased seedlings may result from inocu- 

 lated seed, it is noteworthy that not all inoculated seeds yield diseased 

 seedlings in soil. Owing largely to the profusion of other organisms 

 on the seeds, the methods of anthracnose detection used with the 

 commercial seed, as summarized in Table V, show a low efficiency 

 when applied to seed known to be heavily inoculated with the fungus. 



i Carsner, E. Op. cit. 



