PATHOLOGICAL HISTOLOGY OF STRAWBERRIES AF- 

 FECTED BY SPECIES OF BOTRYTIS AND RHIZOPUS 



By Neil E. Stevens, 

 Pathologist, Fruit Disease ItivestigatiotJ-s, Bureau of Plant Industry 



INTRODUCTION 



The fungi causing rots of strawberries (Fraqaria spp.) in transit from 

 the Southern States have been under investigation by Dr. C. L. Shear, 

 Mr. R. B. Wilcox, and the writer for the past two years. From the first 

 it has been apparent that two species were chiefly responsible for their 

 decay during shipment and on the market. These were Botrytis (cinerea?) 

 and Rhizopus {nigricans}).'^ The effect of these two fungi on ripe straw- 

 berries is strikingly different. Berries injured by Botrytis sp. show a 

 characteristic dryrot — that is, they retain their shape, shrivel somewhat, 

 and no leaking of juice is evident; whereas berries rotted by Rhizopus 

 sp. quickly flatten out, with the loss of a large amount of juice. Such 

 berries are characterized as "leaks" by growers and dealers. 



F. L. Stevens - has already recognized a species of Rhizopus as the 

 probable cause of leak. He, however, considers (p. 950) that Botrytis sp. 

 "is the primary cause of the molding, that the Botrytis initiates the decay, 

 opening the way to such other saprophytes as may be present; of such 

 saprophytes, Rhizopus is by far the most prominent and most abundant." 

 In order to determine if possible the relations of these fungi in rotting 

 strawberries and in particular what differences exist in their method of 

 attack on the fruit, a study of strawberries affected by these fungi was 

 undertaken. 



EXPERIMENTAL METHODS 



The strawberries examined were chiefly of the Klondike variety grown 

 in Louisiana during the season of 191 5. Berries of other varieties grown 

 in South Carolina and at Arlington Experimental Farm, Va., in 191 5, as 

 well as the Missionary and Klondike varieties from Florida in 191 6, were 

 used for comparison. Naturally infected berries as well as sound berries 

 inoculated with spores and mycelium from pure cultures were used in 

 both cases. 



The material was fixed in a solution of equal parts of absolute alcohol 

 and glacial acetic acid. This fluid penetrates very rapidly, so that 

 whole strawberries are satisfactorily fixed. In the case of large berries, 



' In the present uncertainty regarding the taxonomy of these genera it seems unwise to attempt a definite 

 determination of the species. Permanent mounts of the material described are preserved, however, and 

 cultures of the species considered are retained for further study. 



^ Stevens, F. L- A destructive strawberry disease. In Science, n. s., v. 39, no. 1017, p. 949-950. 1914. 



Journal of Agricultural Research, Vol. VI, No. 10 



Dept. of Agriculture, Washington, D. C. June 5, 1916 



dz G— 82 



(361) 



