566 Journal of Agricultural Research vol. vi. no. i S 



OTHER FUNGI ISOLATED AND STUDIED 



In storing on the ground a crop such as dasheens it is only natural that 

 a number of saprophytes would be associated with the storage-rot 

 organism. Two species of Fusarium, F. oxysporum and F. caudatum, 

 were frequently isolated under such conditions. Although preliminary 

 inoculation experiments made by inserting spores and hyphae of these 

 organisms with a needle or by smearing spores on a cut surface of the 

 tubers in a moist chamber gave negative results, it was still believed 

 that they would produce true storage-rots under the proper conditions. 

 As the writer believed that sufficient moisture was lacking, the tubers, 

 after being dipped in spore suspension in sterile water, were wrapped 

 with wet filter paper and then with oiled paper and placed in a moist 

 chamber. The results were negative. Tubers soaked for one hour in 

 water and then dipped in a spore suspension and wrapped in filter paper 

 and oiled paper remained sound. Again, tubers kept at a temperature 

 of about 12 C. for 10 days, inoculated and manipulated as above, and 

 kept in a moist chamber yielded no result. It was finally concluded from 

 these results, in view of the fact that other organisms readily cause 

 storage-rots under laboratory conditions, that these two fungi were 

 merely saprophytes. A species of Phomopsis isolated from dasheens 

 from the Hawaiian Islands failed to produce a rot under any of the con- 

 ditions tried. Other fungi isolated a few times but not studied were 

 Rhizopus nigricans, Penicillium spp., Pythium debaryanum, Fusarium 

 redolens, and an undetermined species of Fusarium. 



A number of inoculations were made with Diplodia zeae, Sphaeropsis 

 malorum, and a species of Diplodia from salix, none of which produced 

 a rot. 



MOISTURE AS A FACTOR IN PRODUCING ROT 



It is likely that moisture plays a far greater part in the production of 

 storage- rots than is generally conceded. Ordinarily it might be sup- 

 posed that the amount of humidity in a moist chamber lined with satu- 

 rated filter paper would be sufficient to germinate the spores of most 

 fungi. Fusarium solani under those conditions would not invade the 

 tissue of dasheens; but if they were sprayed twice a day for one or two 

 days so that the spores would be suspended in a film of water germina- 

 tion and invasion of the tissue would take place before an impenetrable 

 corky layer had formed over the wound. Some root crops have the 

 power to absorb a considerable quantity of water, so that even though 

 water of condensation may be formed on the glass of a moist chamber, 

 the specimen inside is comparatively dry. For example, five tubers of 

 dasheens with a total weight of 558 gm. absorbed 21 gm. of water in 

 24 hours, or more than 3.7 per cent of their original weight; and ten 

 sweet potatoes from storage with a total weight of 1,539 g m - absorbed 

 84 gm. in two hours, or nearly 5.5 per cent of their original weight. Both 



