Detection and Quantification of Airborne Conidia of Fusarium circinatum , the Causal Agent of Pine Pitch Canker, from Two California Sites by Using a Real-Time PCR Approach Combined with a Simple Spore Trapping Method

Abstract

Pinus radiata (Monterey pine), a tree native to coastal California and Mexico, is widely planted worldwide for timber production. A major threat to Monterey pine plantations is the fungal disease pine pitch canker, caused by Fusarium circinatum (Hypocreales). We present a novel trapping approach using filter paper in combination with a rapid molecular method to detect the presence of inoculum in the air. The assay is also useful for diagnosing the presence of the pathogen on plants. The test is based on the F. circinatum specific primer pair CIRC1A-CIRC4A, which amplifies a 360-bp DNA fragment in the intergenic spacer region of the nuclear ribosomal operon. Real-time PCR was used to calculate the number of fungal spores present in each reaction mixture by comparing the threshold cycle (Ct) of unknown spore samples to the Ct values of standards with known amounts of F. circinatum spores. The filter paper method allows prolonged and more sensitive spore sampling in the field compared to traditional traps using petri dishes filled with selective medium. A field test at two sites in coastal California infested with pine pitch canker was carried out during the summer and fall of 2002. Spore counts were in the range of ca. 1 ؋ 10 3 to ca. 7 ؋ 10 5 /m 2 , with the highest spore counts in the fall, suggesting a seasonal fluctuation.

Spore Dispersal Patterns of Fusarium circinatum on an Infested Monterey Pine Forest in North-Western Spain

“…A possible explanation of this incongruence may be related to the contrasting spore trapping mechanisms used in the two studies. The spore traps used here sample the particles occurring directly in the air by impaction on the adhesive surface, while the passive spore traps used by Garbelotto et al [28] and in other research [18,39] sample the spores passively deposited on a filter paper. Passive deposition may be supported by rainfall, as the rain drops trap the air inoculum and deliver it onto the surface of the filter paper.…”

Lights, Rhythms, Infection: The Role of Light and the Circadian Clock in Determining the Outcome of Plant–Pathogen Interactions

“…The incidence and spatial distribution of canker disease in oak trees has been attributed to the need for synchronicity of pathogen activity and seasonal host development (Dodd et al, 2008). The peak of sporulation by Phytophtora ramorum and Fusarium circinatum, the casual agents of sudden oak death canker disease and pine pitch canker, respectively, is when the climate is cool and humid (Schweigkofler et al, 2004;Dodd et al, 2008). Dodd et al (2008) demonstrated that the development of sudden oak death canker disease required coincidence of pathogen sporulation and activity of the host cambial tissue, and they found a strong correlation between date of largest lesion size and timing of spring bud burst.…”

The pitch canker fungus,Fusarium circinatum: implications for South African forestry

“…These results were obtained by assessing 30-50 asymptomatic seedlings on different occasions, over a one-year period from various nursery beds. The standard molecular identification method developed by Schweigkofler et al (2004) Using the information generated by Crous (2005), and the current establishment costs (pitting, planting and blanking), Mitchell et al (2009) calculated this loss to be R602 ha í1 for the saw timber industry, and R896 ha í1 for the pulpwood industry (Table 1). Extrapolated over South Africa, where approximately 15 000 ha are planted annually to P. patula (DAFF 2008), the impact of F. circinatum on tree survival costs the local forest industry in excess of R11 million per year (Mitchell et al 2009).…”