A high-temperature tolerant species in clade 9 of the genus Phytophthora: P. hydrogena sp. nov.

Abstract

A previously unknown Phytophthora species was isolated from irrigation water in Virginia, USA. This novel species produces abundant noncaducous and nonpapillate sporangia in soil water extract solution. It sometimes produces chlamydospores and hyphal swellings in aged cultures and in Petri's solution. This species has optimum vegetative growth at 30 C and grows well at 35 C. The lowest and highest temperatures for growth are 5 and 40 C. All isolates examined in this study are compatibility type A1 and produce mostly plerotic oospores when paired with an A2 mating-type tester of P. cinnamomi. Sequence analyses of the rDNA internal transcribed spacer (ITS) regions and the mitochondrially encoded cytochrome c oxidase 1 (cox 1) gene placed this species in clade 9 of the genus Phytophthora. These characteristics support the description of this taxon as a new species for which we propose the name P. hydrogena sp. nov. Further phylogenetic and physiological investigations of clade 9 species revealed a high-temperature tolerant cluster including P. hydrogena, P. aquimorbida, P. hydropathica, P. irrigata, P. chrysanthemi, P. insolita, P. polonica and P. parsiana. These species all grow well at 35 C. The monophyly of the species in this heat-tolerant cluster except P. insolita and P. polonica is highly supported by the maximum-likelihood analyses of the ITS and cox 1 sequences.

Recycling Irrigation Reservoir Stratification and Implications for Crop Health and Production

“…For example, approximately 30 Phytophthora species have been recovered from the RIRs. Among these high‐temperature tolerant species, P. aquimorbida , P. hydrogena , P. hydropathica , P. insolita , P. irrigata , and P. virginiana have optimal growth temperature at 35°C (Hong et al ., , , ; Yang and Hong, ; Yang et al ., ). They may be more active in surface water when the temperature reaches 30°C during the stratification period between April and October, and less active at lower depths where the temperature decreases dramatically.…”

A unique species in Phytophthora clade 10, Phytophthora intercalaris sp. nov., recovered from stream and irrigation water in the eastern USA

“…Approximately 80 novel species of Phytophthora have been described since 2000, with 16 of these novel species (plus many provisional species) first recovered from aquatic ecosystems. Specifically, these include P. amnicola (Crous et al, 2012), P. borealis (Hansen et al, 2012), Phytophthora chlamydospora (5Phytophthora taxon Pgchlamydo) (Brasier et al, 2003;Hansen et al, 2015), P. fluvialis (Crous et al, 2011), P. lacustris (Nechwatal et al, 2013), P. moyootj (Crous et al, 2014) and Phytophthora taxon aquatilis (Hong et al, 2012) from stream water, Phytophthora aquimorbida (Hong et al, 2012), P. hydrogena (Yang et al, 2014b), Phytophthora hydropathica (Hong et al, 2010), P. macilentosa (Yang et al, 2014a), P. mississippiae , P. stricta (Yang et al, 2014a) and P. virginiana ) from irrigation water and Phytophthora pluvialis (Reeser et al, 2013) from canopy drip. These species, along with Phytophthora gonapodyides, exemplify endemic and dominant species in aquatic environments worldwide, while their less-frequent presence in terrestrial environments indicates the potential variation in composition of species of Phytophthora between aquatic and terrestrial habitats.…”

“…Excluding species that are well-established plant pathogens (e.g. Phytophthora cinnamomi and P. ramorum), many species of Phytophthora have unresolved host ranges, such as the recently described Phytophthora amnicola (Crous et al, 2012), Phytophthora borealis, Phytophthora riparia (Hansen et al, 2012), Phytophthora fluvialis (Crous et al, 2011), Phytophthora hydrogena (Yang et al, 2014b), Phytophthora macilentosa, Phytophthora stricta (Yang et al, 2014a), Phytophthora mississippiae , Phytophthora moyootj (Crous et al, 2014) and Phytophthora virginiana . While limited information on host specificity does exist, it is assumed that some of these newly described species may be saprophytes of dead organic matter (Brasier et al, 2003;Jung et al, 2011;.…”

Comparative Analysis of Water Quality between the Runoff Entrance and Middle of Recycling Irrigation Reservoirs

“…A variety of plant pathogens including bacteria, fungi and oomycetes are present in the RIRs [23], among which Phytophthora species are the most economically important to nursery production. Phytophthora species, such as P. gonapodyides and P. pini have been reported to survive best at temperature 20-25 °C [9,24] and a few high-temperature tolerant species, such as P. aquimorbida, P. hydrogena, P. hydropathica, P. insolita, P. irrigata, and P. virginiana have an optimal growth temperature of 35 °C [4][5][6][7][8]. Temperature differences between these two sampling points of within 1 °C would not alter the temperature biome for pathogen activities.…”

“…Phosphorous becomes less available to the plants when pH is above 7.2 [3]. Water temperature (T) [4][5][6][7][8][9], pH [10], dissolved oxygen (DO) [11], EC [12] and oxidation-reduction potential (ORP) [13] also affect the survival and growth of plant pathogens in the same reservoirs.…”