Incomplete movement of Cryphonectria hypovirus 1 within a vegetative compatibility type of Cryphonectria parasitica in natural cankers on grafted American chestnut trees

Abstract

Summary American chestnut trees, grafted in 1980 from large survivors, were inoculated in 1982 and 1983 with four white (European) hypovirulent strains of Cryphonectria parasitica, infected with C. hypovirus 1 (CHV1); this hypovirus has been shown to be capable of moving rapidly within the mycelium of a vegetative compatibility (vc) type of C. parasitica in blight cankers. Using a 49‐cell lattice plot, 17.8×17.8 cm, the spatial patterns and frequencies of white and pigmented isolates and white and pigmented vc types were investigated within superficial cankers on the grafts located outside the hypovirulent‐strain‐inoculated zone. Four of six cankers assayed contained white isolates, and three of the four had random spatial patterns of white isolates, based on join‐count statistics. Vc tests, using pigmented isolates and pigmented single‐spore colonies of white isolates, indicated that the majority of white and pigmented isolates recovered from each of two cankers assayed were in one vc type. White and pigmented lattice‐plot cells of the same vc type were frequently in contact with each other, indicating incomplete movement of CHV1 within a vc type. Nine and 10 vc types were found in the two cankers; it is hypothesized that small, white vc type areas in each canker may be a source of CHV1 transmission to the major vc types. Based on join‐count statistics, the spatial pattern of the single, major vc type in one canker was non‐random (aggregated), whereas the other canker had a random major vc type pattern. White and pigmented in vitro variants (sectors) of C. parasitica, that resemble white and pigmented in vivo variants in spatial contact and vc compatibility, were intermediate hypovirulent and virulent on forest American chestnuts, and dsRNA positive and negative, respectively. Incomplete movement of CHV1 within a vc type could be a major cause of the prevalence of pigmented isolates in superficial cankers on chestnut trees.

New formulation and delivery method ofCryphonectria parasiticafor biological control of chestnut blight

“…The recovery rate of Cp 4.2H strain from cankers 1 year after shooting was 37Á5%; and all re-isolated strains were virus infected. These results are in agreement with the most successful biocontrol cases reported in the literature (Hogan and Griffin 2002;Milgroom and Cortesi 2004).…”

Distribution of chestnut blight and diversity of Cryphonectria parasitica in chestnut forests in Bulgaria

“…; S. Bryner, K. Sotirovski, S. Akilli, M. Risteski, C. Perlerou and D. Rigling, unpublished). This might be due to the incomplete movement of CHV‐1 within cankers observed after infection (Hogan and Griffin ). Furthermore, difficulties in isolating CHV‐1 from superficial, healed cankers have been experienced before (Prospero et al.…”

“…In studies where multiple samples had been taken per canker, virus-free and virus-infected C. parasitica isolates were sometimes obtained from the same canker (Prospero et al 2006; S. Bryner, K. Sotirovski, S. Akilli, M. Risteski, C. Perlerou and D. Rigling, unpublished). This might be due to the incomplete movement of CHV-1 within cankers observed after infection (Hogan and Griffin 2002). Furthermore, difficulties in isolating CHV-1 from superficial, healed cankers have been experienced before (Prospero et al 2006; S. Bryner, K. Sotirovski, S. Akilli, M. Risteski, C. Perlerou and D. Rigling, unpublished).…”

Informative value of canker morphology on the presence or absence of virus infection in chestnut blight cankers

“…In addition, incomplete movement of CHV‐1 within the fungal mycelium could have further obscured the expected effects of virus infection on canker morphology. Earlier studies had shown that CHV‐1 did not homogenously diffuse after transmission within the fungal mycelium in cankers and that both virus‐infected and virus‐free canker areas can coexist, at least for some time (Shain and Miller ; Hogan and Griffin ). In this study, we identified CHV‐1 infection in 357 cankers.…”