Factors affecting the occurrence of gangrene (Phoma exigua) in potatoes

Abstract

SUMMARY The presence in soil from Scotland and England of Phoma exigua f. sp. exigua and P. exigua f.sp. foveata, which cause gangrene, is confirmed by isolation, and it is established that infection of tubers occurs before lifting, and after lifting from soil adhering to tubers. The distribution of the disease is related to soil moisture, gangrene being most prevalent in tubers from the north‐eastern counties of Scotland where the moisture content of arable soils remains high throughout the growing season. The incidence of the disease may be affected by the haulm, either as a source of infection—though not an important source—or by its effect on the maturity of the tubers. The incidence of gangrene is less where haulm destruction is rapid. The incidence of gangrene in a crop is not related to its incidence in the seed tubers planted and, unless infection is severe, the effect on yield is not serious. Symptoms of skin necrosis were associated with tubers from acid soils, infected with P. exigua f.sp. foveata and stored at low temperature.

Laboratory assessments of the susceptibility of potato tubers to gangrene (Phoma exigua var. foveata)

“…Although Maris Piper had relatively few tubers with lesions over 5 mm in diameter, there were some tubers with small, corky rots immediately surrounding a wound. Also on some Majestic tubers there were very large superficial lesions with mycelium packed in between the phellem and the cortical tissue, the condition described by Malcolmson & Gray (1968) as skin necrosis. Arcsin transformed data, means of three methods of wounding and various intervals between inoculation and wounding.…”

Crop rotation in relation to crop protection

“…Infection of the tubers takes place mainly through wounds caused at harvest and other handling operations especially during riddling. The role of tuber-borne inoculum is well documented (Logan, 1974), but it has also been established that P. exigua var.foveata can invade soils, although it does not appear to be a highly persistent soil inhabitant (Todd and Adam, 1967;Kahn and Logan, 1968;Malcolmson and Gray, 1968). 'Land, which had produced a gangrene-affected crop in the previous year may carry over the winter a level of soil-borne inoculurn sufficiently high to override the effect of tuber-borne inoculum' (Logan, 1974).…”

Phoma Diseases: Identification, Epidemiology, and Strategies for Management

“…Survival of soil-borne pathogens and their capability to infect the host crops in the next season depend mainly on temperature and moisture of the soil (Raaijmakers et al 2009;Smolińska and Kowalska 2018). Potato gangrene disease severity was highest in areas having highest soil moisture content which is very necessary for growth and sustainability of the pathogen (Malcolmson and Gray 1968).…”