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United States Department of Agriculture

Agricultural Research Service

Research Project: Production Management Research For Horticultural Crops in the Gulf South

Location: Southern Horticultural Research

Title: Two novel species representing a new clade and cluster of Phytophthora

item Yang, Xiao
item Copes, Warren
item Hong, Chuanxue

Submitted to: Fungal Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/5/2013
Publication Date: 1/1/2014
Citation: Yang, X., Copes, W.E., Hong, C. 2014. Two novel species representing a new clade and cluster of Phytophthora. Fungal Biology. 118:72-82.

Interpretive Summary: Two previously unknown Phytophthora species were recovered from irrigation water in Mississippi. Since many Phytophthora species are destructive plant pathogens, it is important to identify potential threats to plant production. A physical description of the fungus-like organism was made, growth rates were measured from 9 to 104°F and it was genetically compared to other Phytophthora species. Based on the morphological, physiological and phylogenetic features, this new species is described as Phytophthora stricta sp. nov. and Phytophthora macilentosa sp. nov. This information will allow the organism to be formally identified when researchers, crops advisors and extension specialists sample for potential pathogens in ponds used to irrigate commercial ornamental plant nursery crops.

Technical Abstract: Two novel species of Phytophthora recovered from nursery irrigation water in Mississippi are described as Phytophthora stricta sp. nov. and P. macilentosa sp. nov. Phytophthora stricta produces nonpapillate and partly caducous sporangia, which is characterized by 1 to 3 constrictions of the sporangiophore. Phytophthora macilentosa produces nonpapillate and noncaducous sporangia, which are mostly elongated obpyriform with a high length to width ratio. All examined isolates of these two species are A1 mating type. DNA sequencing of the internal transcribed spacer (ITS) region and the mitochondrial cytochrome c oxidase 1 (cox 1) gene placed P. macilentosa in the high-temperature tolerant cluster within clade 9 of the genus Phytophthora. ITS sequences placed P. stricta in a potentially new ITS clade, which is basal to clades 1 to 8 of Phytophthora. The cox 1 sequence of P. stricta is close to those of species in subclade 8a. The implications of results in this study are discussed.

Last Modified: 07/28/2017
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