The effect of time of planting inoculated tubers on the incidence of potato blackleg and gangrene

Abstract

S U M M A R YIn a series of trials in the years of 1973-76 inclusive, chitted seed tubers of potato cvs Ulster Sceptre, Majestic and Pentland Crown were immersed immediately before planting, on three dates in each year, in water, suspensions of Erwinia carotovora var. atroseptica, Phoma exigua var. foveata or a mixture of both. The development of blackleg was greatest in cv. Ulster Sceptre and most rapid after late planting. Its final incidence was not closely related to date of planting except in cv. Pentland Crown which was least affected when planted late.Combined inoculum of P. exigua var. foveata and E. carotovora var. atroseptica increased five-fold the number of plants that failed to emerge and often retarded early growth of the remainder. Failure to emerge was more frequent the earlier seed tubers were planted. Yield was affected most by blanking and blackleg in the Erwiniainoculated plots and was also reduced by the pre-plant dip in a P. exigua var. foveata suspension, especially after early planting.Seed dipped in the mixed suspensions yielded progeny that after wounding and cool storage developed a lower incidence of gangrene than progeny from seed dipped in P. exigua var. foueata alone. There was no evidence that planting time influenced the incidence of gangrene during storage.

A comparison of methods of seed tuber inoculation for assessing the susceptibility of potato cultivars to blackleg (Erwinia carotovora subsp. atroseptica) in the field

“…The failure of the virus tested stem cutting (VTSC) scheme to eliminate blackleg (Erwinia carofovora subsp. atrosepficu (van Hall) Dye) from seed stocks in the United Kingdom (PCrombelon, Lowe, Quinn & Sells, 1980) and the lack of a proven commercially available bactericide (Harris, 1979;Lund & Wyatt, 1979) have increased interest in the differences in field susceptibility between existing cultivars (Logan & Copeland, 1979;PCrombelon & Lowe, 1982;Lapwood & Gans, 1984) and in the forms of resistance that might be incorporated into a breeding programme.…”

“…Various methods for the inoculation of seed tubers prior to field assessment have been proposed. These include, dipping at harvest (Maas Geesteranus & Vruggink, 1976) or prior to planting (Logan & Copeland, 1979), stabbing with an impregnated tooth pick (Hossain & Logan, 1983) or needle (Logan, 1969;Lapwood & Legg, 1983), or injection by high pressure jet (Wastie, 1984), or under vacuum (Perombelon & Lowe, 1979;McGuire & Kelman, 1984).…”

A comparison of methods to evaluate the susceptibility of potato cultivars to blackleg (caused by Erwinia carotovora subsp. atroseptica) in the field at different sites

“…Others expose undamaged tubers to inoculum by dipping them in a bacterial suspension (Maas Geesteranus & Vruggink. 1976;Logan & Copeland, 1979) or by infiltration under vacuum (Perombelon & Lowe, 1979;McGuireA Kelman, 1984), whilst Lapwood & Read (1986a) used a combination of damaging or cutting the skin of seed tubers and vacuum infiltration.…”