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

Abstract

Disease incidence was recorded in tubers of various cultivars following inoculation with macerated mycelium oi Phoma exigua var.foveata and wounding in various ways. A method which produced predominantly crush wounds gave most rots and the most consistent results. The length of time between inoculation and wounding did not significantly affect the incidence of disease but disease severity did increase with damage infliction time. Inoculated, undamaged tubers produced rots but the incidence was low and discrimination between cultivars was poor when compared with damaged tubers. In some tests the resistance to gangrene could be measured by the proportion of tubers affected, in others all tubers had lesions but the extent of infection was different. The latent period of the disease differed between cultivars. Rate of lesion development was constant over a period of 12 wk within cultivars but differed between them.

The influence of cultivar and isolate on the development of gangrene (Phoma exigua var. foveata) in potato tubers

“…In a comparison of variance components, cultivar contributed approximately seven times more to the variation in lesion size than did isolate. This result is likely to have overestimated the relative contribution of isolate to gangrene development since the tuber inoculation method used circumvented an important component of tuber resistance, namely resistance to mechanical damage (Wellving, 1976;Jellis, 1982).…”

“…var. foueata (Foister) Boerema) depends on the isolate used to inoculate the tubers (Rogers & Killick, 1975;Jellis, 1978;1981): another study suggests this is not the case (Bain, Lennard & Wastie, 1982), although these workers have demonstrated substantial variation in pathogenicity among isolates of P . exigua var.…”

Methods of inoculation of potato tubers when assessing resistance to Phoma exigua

“…Оцінка прояву хвороби проводиться через 2 місяці після зараження. Стійкість проти хвороби оцінюється за кількістю уражених бульб, а при ураженні всіх бульб -за інтенсивністю ураження [11].…”

The influence of cultivar and mechanical damage on the relationship between inoculum concentration of Phoma exigua var. foveata on potato tubers and gangrene development

“…However, several other factors are known to influence gangrene development and may, therefore, modify the relationship between inoculum concentration and disease development. Two of the most important are the incidence and severity of mechanical damage (Todd & Adam, 1967;Malcolmson & Gray, 1968;Walker & Wade, 1976;Hide et al, 1977) and variation in resistance among cultivars (Malcolmson, 1958;Todd & Adam, 1967;Langton, 1971Langton, , 1972Wellving, 1976;Bain et al, 1982;Jellis, 1982). This paper describes experiments which examined the influence of cultivar and tuber damage on the relationship between the amount of inoculum applied to the tuber and the resulting development of gangrene.…”