Browsing by Author "Hong, C."
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- Diversity and community structure of cyanobacteria and other microbes in recycling irrigation reservoirsKong, P.; Richardson, P.; Hong, C. (PLOS, 2017-03-16)
- Oxygen stress reduces zoospore survival of Phytophthora species in a simulated aquatic systemKong, P.; Hong, C. (Biomed Central, 2014-05-13)Background The genus Phytophthora includes a group of agriculturally important pathogens and they are commonly regarded as water molds. They produce motile zoospores that can move via water currents and on their own locomotion in aquatic environments. However, zoosporic response to dissolved oxygen, an important water quality parameter, is not known. Like other water quality parameters, dissolved oxygen concentration in irrigation reservoirs fluctuates dramatically over time. The aim of this study was to determine whether and how zoospore survival may be affected by elevated and low concentrations of dissolved oxygen in water to better understand the aquatic biology of these pathogens in irrigation reservoirs. Results Zoospores of P. megasperma, P. nicotianae, P. pini and P. tropicalis were assessed for survival in 10% Hoagland’s solution at a range of dissolved concentrations from 0.9 to 20.1-mg-L-1 for up to seven exposure times from 0 to 72-h. Zoospore survival was measured by resultant colony counts per ml. Zoospores of these species survived the best in control Hoagland’s solution at dissolved oxygen concentrations of 5.3 to 5.6-mg-L-1. Zoospore survival rates decreased with increasing and decreasing concentration of dissolved oxygen, depending upon Phytophthora species and exposure time. Overall, P. megasperma and P. pini are less sensitive than P. nicotianae and P. tropicalis to hyperoxia and hypoxia conditions. Conclusion Zoospores in the control solution declined over time and this natural decline process was enhanced under hyperoxia and hypoxia conditions. These findings suggest that dramatic fluctuations of dissolved oxygen in irrigation reservoirs contribute to the population decline of Phytophthora species along the water path in the same reservoirs. These findings advanced our understanding of the aquatic ecology of these pathogens in irrigation reservoirs. They also provided a basis for pathogen risk mitigation by prolonging the turnover time of runoff water in recycling irrigation systems via better system designs.
- Phytophthora species recovered from irrigation reservoirs in Mississippi and Alabama nurseries and pathogenicity of three new speciesCopes, W. E.; Yang, X.; Hong, C. (2015)
- Phytophthora xstagnum nothosp nov., a New Hybrid from Irrigation Reservoirs at Ornamental Plant Nurseries in VirginiaYang, X.; Richardson, P. A.; Hong, C. (PLOS, 2014-07-29)
- Soil bacteria as sources of virulence signal providers promoting plant infection by Phytophthora pathogensKong, P.; Hong, C. (Nature Publishing Group, 2016-09-12)
- Soil inoculum production, survival, and infectivity of the boxwood blight pathogen, Calonectria pseudonaviculataDart, N. L.; Hong, C.; Craig, C. A.; Fry, J. T.; Hu, X. R. (2015)
- Worldwide forest surveys reveal forty-three new species in Phytophthora major Clade 2 with fundamental implications for the evolution and biogeography of the genus and global plant biosecurityJung, T.; Milenkovic, I.; Balci, Y.; Janousek, J.; Kudlacek, T.; Nagy, Z. A.; Baharuddin, B.; Bakonyi, J.; Broders, K. D.; Cacciola, S. O.; Chang, T. -T.; Chi, N. M.; Corcobado, T.; Cravador, A.; Dordevic, B.; Duran, A.; Ferreira, M.; Fu, C. -H.; Garcia, L.; Hieno, A.; Ho, H. -H.; Hong, C.; Junaid, M.; Kageyama, K.; Kuswinanti, T.; Maia, C.; Majek, T.; Masuya, H.; Lio, G. Magnano di San D. S.; Mendieta-Araica, B.; Nasri, N.; Oliveira, L. S. S.; Pane, A.; Perez-Sierra, A.; Rosmana, A.; von Stowasser, E. Sanfuentes; Scanu, B.; Singh, R.; Stanivukovic, Z.; Tarigan, M.; Thu, P. Q.; Tomic, Z.; Tomsovsky, M.; Uematsu, S.; Webber, J. F.; Zeng, H. -C.; Zheng, F. -C.; Brasier, C. M.; Jung, M. Horta (Westerdijk Fungal Biodiversity Institute, 2024)During 25 surveys of global Phytophthora diversity, conducted between 1998 and 2020, 43 new species were detected in natural ecosystems and, occasionally, in nurseries and outplantings in Europe, Southeast and East Asia and the Americas. Based on a multigene phylogeny of nine nuclear and four mitochondrial gene regions they were assigned to five of the six known subclades, 2a-c, e and f, of Phytophthora major Clade 2 and the new subclade 2g. The evolutionary history of the Clade appears to have involved the pre-Gondwanan divergence of three extant subclades, 2c, 2e and 2f, all having disjunct natural distributions on separate continents and comprising species with a soilborne and aquatic lifestyle and, in addition, a few partially aerial species in Clade 2c; and the post-Gondwanan evolution of subclades 2a and 2g in Southeast/East Asia and 2b in South America, respectively, from their common ancestor. Species in Clade 2g are soilborne whereas Clade 2b comprises both soil-inhabiting and aerial species. Clade 2a has evolved further towards an aerial lifestyle comprising only species which are predominantly or partially airborne. Based on high nuclear heterozygosity levels ca. 38 % of the taxa in Clades 2a and 2b could be some form of hybrid, and the hybridity may be favoured by an A1/A2 breeding system and an aerial life style. Circumstantial evidence suggests the now 93 described species and informally designated taxa in Clade 2 result from both allopatric non-adaptive and sympatric adaptive radiations. They represent most morphological and physiological characters, breeding systems, lifestyles and forms of host specialism found across the Phytophthora clades as a whole, demonstrating the strong biological cohesiveness of the genus. The finding of 43 previously unknown species from a single Phytophthora clade highlight a critical lack of information on the scale of the unknown pathogen threats to forests and natural ecosystems, underlining the risk of basing plant biosecurity protocols mainly on lists of named organisms. More surveys in natural ecosystems of yet unsurveyed regions in Africa, Asia, Central and South America are needed to unveil the full diversity of the clade and the factors driving diversity, speciation and adaptation in Phytophthora.