Abstract
The existence of a latent stage within host tissue of the pine pathogens Fusarium circinatum and Diplodia sapinea, the causal agents of pitch canker and shoot blight disease respectively, has previously been cited. However, studies on this cryptic phase in each disease lifecycle has only been focused on the host aerial parts but not on the roots. Therefore, our objective was to analyze the presence of both pathogens in roots of non-symptomatic mature trees in plantations where the pathogens are known to be causing canker symptoms. For that, we sampled roots from ten non-symptomatic and ten symptomatic trees in three Pinus radiata and one Pinus pinaster plantations in Basque Country, Spain. Both pathogens were isolated from roots of non-symptomatic trees in a higher frequency than from roots of symptomatic trees, 23.3% and 6.6% respectively for D. sapinea and 16.6% and 3.3% respectively for F. circinatum. Neither pathogens was detected in the P. pinaster plantation. The two pathogens were never isolated from the same tree. A high molecular variability was observed for D. sapinea isolates with six different haplotypes and two mating types for the eleven characterized isolates, but only one haplotype and mating type was found for F. circinatum, with all isolates of both fungi being proved pathogenic. These results evidence the importance root infection may have in the disease lifecycle and, therefore, disease management.
Highlights
IntroductionFusarium circinatum Nirenberg and O’Donnell 1998 [1] and Diplodia sapinea (Fr.) Fuckel [2] are two of the most important pathogens that affect Pinus species causing canker diseases, and can result in significant economic losses in nurseries, plantations and natural forests worldwide [3,4,5,6,7,8].Forests 2018, 9, 128; doi:10.3390/f9030128 www.mdpi.com/journal/forestsDisease establishment and severity of pine pitch canker seem to be determined by climatic conditions.A temperature range of 20–25 ◦ C and high humidity favor spore germination, mycelial growth and infection [3,9]
Fusarium circinatum was only isolated from roots at the Bizkaia plantation (6 isolates from 6 trees) where half of sampled roots of non-symptomatic tress (5 roots out of 10) were colonized by the pathogen
We report the presence of the pine pathogens, Fusarium circinatum and Diplodia sapinea, in roots of non-symptomatic trees of Pinus radiata in the Basque Country, Spain
Summary
Fusarium circinatum Nirenberg and O’Donnell 1998 [1] and Diplodia sapinea (Fr.) Fuckel [2] are two of the most important pathogens that affect Pinus species causing canker diseases, and can result in significant economic losses in nurseries, plantations and natural forests worldwide [3,4,5,6,7,8].Forests 2018, 9, 128; doi:10.3390/f9030128 www.mdpi.com/journal/forestsDisease establishment and severity of pine pitch canker seem to be determined by climatic conditions.A temperature range of 20–25 ◦ C and high humidity favor spore germination, mycelial growth and infection [3,9]. Fusarium circinatum Nirenberg and O’Donnell 1998 [1] and Diplodia sapinea (Fr.) Fuckel [2] are two of the most important pathogens that affect Pinus species causing canker diseases, and can result in significant economic losses in nurseries, plantations and natural forests worldwide [3,4,5,6,7,8]. Disease establishment and severity of pine pitch canker seem to be determined by climatic conditions. Diplodia sapinea is among the most common causes of damage to plantation-grown pines in Spain [17,18] and disease outbreaks usually depend on climatic condition such as hail, drought or heat wave [19,20]. Highly susceptible to both fungi [23,24], whereas Pinus pinaster Ait. shows moderate resistance [5]
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