A COMPARISON OF THE PKCTINASE PRODUCED BY 

 DIFFERENT SPECIES OF RHIZOPUS 



By ly. ly. Harter, Pathologist, and J. L. Weimer, Pathologist, Office of Cotton, Truck, 

 atid Forage Crop Disease Investigations, Bureau of Plant Industry, United States 

 Department of Agriculture 



INTRODUCTION 



Recent investigations by Harter and Weimer ^ showed that Rhizopus 

 tritici Saito, an organism demonstrated to be parasitic on sweet potatoes, 

 produces a powerful intracellular and extracellular pectinase which 

 dissolves the middle lamella so that the cells readily separate without 

 themselves undergoing any noticeable alteration. A suspension of 0.25 

 gm. of the enzym powder in 25 cc. of water was found to completely 

 macerate sweet potato disks i mm. in thickness in two to five hours. 

 Furthermore, the solution on which the fungus grew was even richer 

 in pectinase, maceration of the sweet potato disks being completed in 

 one to three hours. 



Since the foregoing results have been published Harter, Weimer, and 

 Lauritzen ^ have concluded experiments which showed that out of 1 1 

 species of Rhizopus studied 9 were parasitic on the sweet potato. 

 Furthermore, these investigators found that the species differed in 

 degree of parasitism, both as regards the percentage of infection and 

 the rapidity of decay. 



The present investigations, therefore, had for their object to determine 

 (i) if pectinase is produced by all species of Rhizopus and, if so, to what 

 extent and (2) if its production is any indication of the parasitism of 



the species. 



TECHNIC 



The methods employed in carrying out macerating experiments 

 with the different species of Rhizopus were for the most part the same as 

 those used in previous work to which reference ^ has already been made, 

 although some slight modifications were necessary to meet certain phases 

 of the problem. Three sets of experiments were carried out with each 

 organism. All the species were included in a single experiment and the 

 macerating action was determined for all at the same time, so that the 

 results for each species are directly comparable for a single experiment. 

 The culture medium was so prepared and in sufficient quantity as to make 



1 Harter, L. I,., and Weimer, J. L. studies in the physiology of parasitism with speciai, refer- 

 ence TO THE SECRETION OF PECTINASE BY RHIZOPUS TRITICI SAITO. In Jour. Agr. Research, v. 21, no. 9, 

 p. 609-625. 1921. Literature cited, p. 624-625. 



* Harter, L. I,-, Weimer, J. L-, and Laitritzen, J. I. the susceptibility of the different varie- 

 ties OF SWEET potatoes TO DECAY BY RHIZOPUS NIGRICANS AND RHIZOPUS TRITICI. In Phytopathology, 

 V. II. 1921. In press. 



Journal of Agricultural Research, Vol. XXII, No. 7 



Washington, D. C. Nov. 12, 1921 



aam Key No. G-354 



(371) 



