Abstract
With future global temperatures predicted to increase, the relationship between a host, pathogen, and environment, becomes less predictable and epidemics may pose a greater risk to forests worldwide. Resistance breeding is an important disease management tool, but because tree species require long breeding times, it is necessary to develop techniques for testing current pathogen isolates against their hosts. Pitch canker disease of pines, caused by the pathogen Fusarium circinatum, is no exception and represents a threat to pine forests and commercial plantations worldwide, as it thrives at warm temperatures and high humidity. We tested growth of 15 F. circinatum isolates in culture at three temperatures: 25, 27, and 31 °C. We also evaluated the sporulation and pathogenicity of eight of the isolates on two susceptible Pinus elliotti (slash pine) open-pollinated families and one tolerant open-pollinated Pinus taeda (loblolly pine) family. Our results showed significant differences among isolates in the temperature and pathogenicity tests. All isolates showed a significant decrease in growth at 31 °C, although some showed similar growth at 25 and 27 °C. Several of the new isolates tested were more pathogenic than the isolates that the USDA Forest Service Resistance Screening Center (RSC) had been using. The new isolates have now been incorporated into their operational screening program.
Highlights
Pitch canker, caused by the necrotrophic fungus Fusarium circinatum Nirenberg and O’Donnell, is one of the major diseases of pines, affecting 57 pine species [1,2,3], but Douglas-fir (Pseudotsuga menziesii) is susceptible [4]
Fusarium circinatum isolates from 13 Florida and Georgia counties were obtained from field samples of infected loblolly (Pinus taeda) or slash (Pinus elliottii) pine tissue or from previously dried
Fusarium circinatum isolates from 13 Florida and Georgia counties were obtained from field mycelia stored at 4 ◦ C (Figure 1)
Summary
Pitch canker, caused by the necrotrophic fungus Fusarium circinatum Nirenberg and O’Donnell, is one of the major diseases of pines, affecting 57 pine species [1,2,3], but Douglas-fir (Pseudotsuga menziesii) is susceptible [4]. It causes resinous lesions in stems and branches and affects reproductive structures [5], thereby reducing fertility [1]. Both the pathogen and the host are easy to grow under controlled conditions, facilitating experimental work to test for response under diverse environments
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