Sweetpotato cultivar susceptibility to infection by <i>Ceratocystis fimbriata</i>

Abstract

The fungus Ceratocystis fimbriata causes a disease of the sweetpotato (Ipomoea batatas) plant commonly known as black rot This study evaluated sweetpotato cultivar susceptibility to C fimbriata infection During crop production infection of sweetpotato storage roots may take place by transmission from contaminated transplants but generally the pathogen is introduced directly through openings in the periderm These openings may take the form of damaged secondary lateral roots lenticels or wounds In a laboratorybased bioassay storage roots were punctured then pointinoculated with the pathogen Following incubation under warm humid conditions the dimensions of black rot lesions were compared The predominant New Zealand cultivar Owairaka Red was demonstrably less susceptible to C fimbriata than the Japanese cultivar Beniazuma but significantly more susceptible than Beauregard from the United States of America (P<0001) The rate of increase in lesion diameter for the most susceptible cultivar assessed was almost twice that of the least susceptible