Categorisation of reactions and enumeration of bacteria in potato cultivars inoculated with the causal agent of bacterial ring rot

Abstract

Variability in the responses of plants propagated from in vitro tissue cultures of 52 ware and industrial potato cultivars to different Clavibacter michiganensis subsp. sepedonicus inoculum size was tested during 2015–2017. Bacterial ring rot symptoms on plants and tubers xylem vessels were recorded for 8 weeks and the susceptibility index (SI) for individual cultivars was calculated. Based on foliage symptoms, potato cultivars were placed into three symptoms groups. The symptomless group had SIs ≤ 1, for the moderate symptom group SIs ranged from 1.01 to 2.99, and the severe symptom group had SIs ≥ 3.0. The pathogen concentrations in vascular vessels of all infected potato plants increased during the experiment regardless of the foliage symptom group.