Determination of incidence of potato soft rot in major potato growing areas of Punjab, Pakistan

Abstract

Bacterial soft rot caused by Erwinia carotovora is a serious disease and can cause substantial post-harvest losses to potato. Its presence has been reported from Punjab, but current prevalence is not reported. Current study was initiated to assess the incidence of bacterial rot disease in Punjab. Survey of potato growing areas of Punjab (which include fields and markets) was conducted twice to assess the disease incidence and severity. Major districts included Lahore, Okara, Faisalabad, Sahiwal, Sialkot and Taxila. Several fields from each district were randomly visited and the samples of plants, tubers and soil were collected. Crystal violet pectate (CVP) medium was used for isolation of E. carotovora. Bacterial soft rot was prevalent in the fields and incidence ranged from 2-7% and highest incidence was found 7% in Sialkot. Market survey revealed the incidence of soft rot relatively higher as compared to field. The rot suspected samples were plated on CVP media and the characteristic pit formation was observed. Eight (8) isolates were obtained with pit formation feature and preliminary identification was based on the growth on CVP media at 27, 33.5 and 37 °C. Three strains were found associated to rot as E. carotovora subsp. atroseptica, E. carotovora subsp. carotovora and E. chrysanthemi. The isolates were further confirmed using biochemical tests. Pathogenicity was tested on tuber slices which exhibited the rot symptoms.