A rapid method to estimate the resistance of cold stored carrot roots to Botrytis cinerea

Abstract

SUMMARYInoculating whole carrot roots at 4°C with mycelial/agar discs of the grey mould fungus Botrytis cinerea gives a measure of their resistance and hence storage potential to this pathogen, but results are not obtained for at least 33 days. In the present investigation a more rapid method was used which involved inoculating root slices with spore suspensions containing 5 × 103–5 × 106 spores/cm3 at 24°C. Resistance was assessed visually and by a chitin estimation 48 h after inoculation.Both methods were used to measure the resistance of cold stored carrot roots during two storage seasons, 1976/77 and 1977/78. In each season there was a particular inoculum level which most clearly recorded the increasing susceptibility of roots with time in store. In 1976/77 this was 1 × 105 spores/cm3 whereas in 1977/78 it was the lower inoculum concentration of 5 × 104 spores/cm3, suggesting the roots were generally more susceptible in 1977/78 than the previous season. This was in accord with the results from the whole root method of assessment. A chitin estimation proved to be the more sensitive method of assessment for inoculum potential experiments.