Incidence of Colletotrichum coccodes in Certified Potato Seed Tubers Planted in Washington State

Abstract

Incidence of Colletotrichum coccodes in lots of certified seed tubers planted in Washington state, originating from nine western and midwestern states in the United State and two provinces in Canada, ranged from 0 to 90% in 1994 and 0 to 53% in 1995. In 1994, significant interactions between state/province and cultivar, and between seed grower and cultivar, were evident. In 1995, incidence of C. coccodes in seed lots did not vary significantly among states and cultivars. C. coccodes was not isolated from nuclear seed tubers and incidence of infected tubers was higher with higher seed generations. The fungus was isolated from the tuber periderm and outer medulla tissues and isolation frequency was greater from tuber stem ends than from either bud ends or lateral sections. Significantly greater stem infections developed in plants grown from seed tubers in which C. coccodes had been detected than in plants grown from seed tubers from which C. coccodes had not been isolated. This study confirms that C. coccodes is distributed among potato-production areas within seed tubers, and that seed tuber infection increases the incidence of early-season plant infection.

Colonization of Potato Roots and Stolons by Colletotrichum coccodes from Tuberborne Inoculum

“…It also rendered any conidia nonviable prior to root washing (Blakeman and Hornby 1966;Farley 1976) and may have been important in generating the similar results obtained from visual disease diagnosis and root isolations. Infection of some root systems occurred from seed tubers in which C. coccodes was not detected and that were not inoculated in this study probably because C. coccodes was likely present on the lateral or bud end tuber surfaces not sampled (Johnson et al 1997).…”

“…This might explain the frequency with which C. coccodes has been associated with remnant stolons on tubers (Barkdoll and Davis 1992;Dickson 1926;GlaisVarlet et al 2004;Harrison 1963;Stevenson et al 1976) and the greater frequency that the fungus can be isolated from the stolon end than from other areas of the tuber (Johnson et al 1997). Based on the frequency of pathogen detection on the stolon (basal) end of the tuber and the spatial pattern of disease observed in this study, it seems likely that progeny tubers can be infected via the stolon.…”

“…The tubers were assayed to detect natural infection by C. coccodes by extracting the tuber basal end (Johnson et al 1997) and incubating on a modified PDA (MPDA) (Nitzan et al 2006a) in the dark at 22°C for 14 days. Seed-tubers were considered naturally infected when sclerotia of C. coccodes developed on the excised tuber tissue.…”

“…Potato plants become infected from soilborne microsclerotia and from infected seed-tubers (Barkdoll and Davis 1992;Denner et al 1998;Dickson 1926;Johnson et al 1997;Tsror et al 1999). Soilborne inoculum has been recognized as being more aggressive than tuberborne inoculum (Nitzan et al 2008).…”

Partial Resistance to Potato Black Dot, Caused by Colletotrichum coccodes in Solanum tuberosum Group Andigena

“…Hughes. This disease is prevalent in potato production regions and can be of economic concern by itself, or as a part of the potato early dying syndrome (Andrivon et al 1997;Andrivon et al 1998; Barkdoll & Davis 1992;Denner et al 1997;Denner et al 1998;Johnson and Miliczky 1993;Johnson 1994;Johnson et al 1997;Read & Hide 1988;Read & Hide 1995;Tsror (Lahkim) et al 1999; and Johnson 2000). Black dot has been demonstrated to decrease total yields between 16% to 30% (Nitzan et al 2006a;Tsror (Lahkim) et al 1999), causing premature death of the plants (Tsror (Lahkim) and Johnson 2000).…”