Modeling Sporulation of Fusicladium carpophilum on Nectarine Twig Lesions: Relative Humidity and Temperature Effects

Abstract

The production of conidia by Fusicladium carpophilum on twig lesions was quantitatively modeled as a function of temperature and duration of high relative humidity. During peak sporulation periods in 2007, 2008, and 2009, 1-year-old twigs bearing abundant overwintering lesions were removed from a heavily infected 'Redgold' nectarine orchard, placed in trays at high relative humidity (>95%), and incubated at eight constant temperatures for seven durations, resulting in a factorial design of 56 treatment combinations. Conidia numbers were estimated with a hemacytometer. Results from a six-stage modeling process indicated that, at any given temperature, spore production during high relative humidity periods increased in a monomolecular- to Gompertz-like pattern. The Richards model, with shape parameters of 0.79 to 0.90, was found to provide the best overall fit. When the asymptote and rate parameters were derived as functions of temperature using Gaussian and quadratic models, respectively, the duration of high relative humidity and temperature described 90 to 94% of the variation in conidia production. Predictions of the final models were highly correlated with observed levels of sporulation (r > 0.94; P < 0.0001), indicating an excellent fit to the data. The optimum temperature for sporulation, based on fitting a Gaussian model to the maximum sporulation levels at each temperature, was 17.9 to 20.2°C, with an overall average of 18.8°C. The derived models give a quantitative description of sporulation by F. carpophilum and may have potential use in simulators and forecasting systems.

Biology and Epidemiology of Venturia Species Affecting Fruit Crops: A Review

“…and Ramalia Bat) and because phylogenetic analysis of the ITS region demonstrates that the erection of Fusicladosporium results in a polyphyletic genus (Schubert et al, 2003 ; Beck et al, 2005 ). Thus, Fusicladosporium is currently considered a synonym of Fusicladium (Schubert et al, 2003 ; Crous et al, 2007 ; Scherm et al, 2008 ; Seyran et al, 2009 ; Lalancette et al, 2012 ).…”

“…Venturia inaequalis, V. pyrina, V. nashicola , and V. cerasi form pseudothecia in detached leaves on the orchard ground (Schweizer, 1958 ; Latorre et al, 1985 ; Umemoto, 1990b ; Spotts and Cervantes, 1994 ; Machardy, 1996 ; Rossi et al, 2001 ; Eguchi and Yamagishi, 2007 ; Lian et al, 2007 ). Pseudothecia of V. carpophila were also observed in affected detached leaves of apricot (Fisher, 1961 ), but their epidemiological role is unknown, and the conidia of V. carpophila overwintering in affected twigs are commonly considered the primary inoculum (Lan and Scherm, 2003 ; Lalancette et al, 2012 ). Ascocarps have never been found in nature for F. effusum, F. oleagineum, F. eriobotryae , or F. pyracanthae ; conidia are considered the only form of primary inoculum for these species (Raabe and Gardner, 1972 ; Gottwald and Bertrand, 1982 ; Graniti, 1993 ; González-Domínguez et al, 2014b ).…”

“…Venturia carpophila overwinters as mycelia in lesions on fruit-bearing 1-year-old twigs (Scherm et al, 2008 ; Lalancette et al, 2012 ), and the conidia produced on these lesions act as the primary inoculum. Pseudothecia of V. carpophila were found in overwintering apricot leaves only in a severely affected orchard in Australia (Fisher, 1961 ).…”

“…Pseudothecia of V. carpophila were found in overwintering apricot leaves only in a severely affected orchard in Australia (Fisher, 1961 ). However, the epidemiological role of the teleomorph in the V. carpophila disease cycle remains unknown (Lalancette et al, 2012 ).…”

Morphology, DNA Phylogeny, and Pathogenicity of Wilsonomyces carpophilus Isolate Causing Shot-Hole Disease of Prunus divaricata and Prunus armeniaca in Wild-Fruit Forest of Western Tianshan Mountains, China

“…As conidia mature, they are delimited from conidiogenous cells by a single transverse septum, and multiple (3-7) transverse septa subsequently form as the conidia separate from the conidiogenous cells [26]. Shot-hole disease is most harmful under cool and wet spring conditions, although it can occur and cause damage at any time during the growing season following prolonged wet weather [27,28].…”