PEANUT DISEASES 289 



more discolored or otherwise damaged shells than do other lots. These 

 shell characteristics, however, are sometimes found on shells that do not 

 contain discolored seeds. In some instances the cotyledons beneath dis- 

 colored seed coats are not discolored, but generally there is slight yellow 

 or blue-black discoloration. A few cotyledons underneath discolored seed 

 coats are conspicuously discolored. 



The nitrogen and oil content of blue-damaged seeds and seed coats is 

 not different from that of normal seeds. The discoloration apparently does 

 not result in important changes in chemical constituent of the seeds. Ac- 

 cording to preliminary tests there is no detectable rancidity or off-flavor 

 in blue-damaged seeds nor does the discoloration have any effect on ger- 

 mination of the seeds or vigor of seedlings. 



Organism and Pathogenicity. Numerous unsuccessful attempts to 

 isolate fungi from the discolored spots have been made. In rare instances 

 Sclerotium rolfsii was isolated. It seems apparent, therefore, that the dis- 

 coloration results from chemical reaction of pigments of the seed coat. 

 Several facts were evident : Sclerotium rolfsii grew from a few of the dis- 

 colored spots; it grew readily from shells which contained discolored 

 seeds; it was known to be prevalent in fields in which Spanish peanuts 

 were grown ; and S. rolfsii secretes oxalic acid which diffuses into plant 

 tissue in advance of hyphae. A test was made, therefore, in which crystals 

 of oxalic acid were kept against nuts on living plants in damp soil for 

 72 hours. Typical blue damage resulted. Inoculation of peanuts with S. 

 rolfsii resulted in the production of a considerable percentage of blue- 

 black discolored seeds. Application of liquid from an autoclaved culture 

 of 6". rolfsii to green or partially cured nuts resulted in a lighter form of 

 the discoloration. It seems evident, therefore, that the discoloration is an 

 indicator reaction involving pigments of the seed coat and oxalic acid 

 secreted by 5". rolfsii growing in or on the peanut shells. 



Most fields of Spanish peanuts in the southeastern United States are 

 infested with 5". rolfsii. When weather conditions or curing methods pre- 

 vent the rapid drying out of the curing plants there may be continued 

 growth of S. rolfsii from infested plants in the curing lot. Field studies 

 show an interrelationship between curing methods, weather conditions, 

 and development of blue damage. Prominent discoloration is not found 

 in peanuts cured in stacks during hot, dry weather, but pronounced dis- 

 coloration is found in peanuts cured in stacks during warm, damp 

 weather. The blue-black discoloration does not develop in quick-cured 

 peanuts taken from the same field as peanuts in which blue damage de- 

 velops during slow curing in warm, damp weather. It is apparent, there- 



