Identification of Phytophthora species baited and isolated from forest soil and streams in northwestern Yunnan province, China

Abstract

Phytophthora species were surveyed by collecting soil samples and placing bait leaves in selected streams during June-October in the years 2005, 2006 and 2010 at three sites in oak forests in Diqing Tibetan Autonomous Prefecture of NW Yunnan province, China. Seventy-three isolates of Phytophthora spp. were recovered from 135 baited leaf samples and 81 soil samples. Eight Phytophthora species were identified by observation of morphological features and ITS1-5.8S-ITS2 rDNA sequence analysis. The eight taxa included two well-known species P. gonapodyides and P. cryptogea, two recently described species P. gregata and P. plurivora, two named but as yet undescribed taxa, P. taxon PgChlamydo and P. taxon Salixsoil, and two previously unrecognized species, Phytophthora sp.1 and P. sp.2. The most numerous species, P. taxon PgChlamydo, and the second most abundant species, P. taxon Salixsoil, were recovered at all three sites. Phytophthora cryptogea was detected only once at site Nixi. Phytophthora gregata and P. sp.2 were isolated from a stream only at site Bitahai, while the other three species were each found at two sites. Phylogenetic analysis revealed that the isolates belonged to three ITS clades, one species including six isolates in clade 2, six species including 66 isolates in clade 6 and one species in clade 8. There was a relatively rich species and genetic diversity of Phytophthora detected in the investigated regions where the forest biotic and abiotic factors affecting the growth and evolution of Phytophthora populations were diverse.

Protocolos de aislamiento y diagnóstico de Phytophthora Spp.: enfoque aplicado a la investigación

“…La elección de los tejidos vegetales trampa depende de la especies de Phytophthora que se sospeche es el agente causal de la enfermedad. Las hojas de Rhododendron, Camellia, Quercus, Lupinus, acículas de Juniperus, frutos de manzana, pera y pepino son los de mayor uso mediante los cuales es posible detectar un gran número de especies de Phytophthora (Erwin y Ribeiro, 1996;Ferguson y Jeffers, 1999;Ivors et al, 2004;Balci et al, 2007;Gevens et al, 2007;Sutton et al, 2009;Reeser et al, 2011;Tooley y Carras, 2011;Themann et al, 2002;Huai et al, 2013). Se recupera un mayor número de especies de Phytophthora cuando se usan hojas enteras del tejido vegetal trampa (Ferguson y Jeffers, 1999;Ghimire et al, 2009), que cuando se utlizan discos de hojas, ya que no es recomendable porque son colonizados fácilmente por Pythium y bacterias.…”

“…El segundo consiste en acidificar el medio de cultivo a pH 3, utilizando ácido by which a large number of Phytophthora species can be detected (Erwin and Ribeiro, 1996;Ferguson and Jeffers, 1999;Ivors et al, 2004;Balci et al, 2007;Gevens et al, 2007;Sutton et al, 2009;Reeser et al, 2011;Tooley and Carras, 2011;Themann et al, 2002;Huai et al, 2013). A greater number of Phytophthora species are recovered when whole leaves of the plant tissue trap are used (Ferguson and Jeffers, 1999;Ghimire et al, 2009), than when discs of leaves are used, since it is not recommended because they are easily colonized for Pythium and bacteria.…”

Phytophthora Species Emerging as Pathogens of Forest Trees

“…Similar numbers of species and many of the same taxa are reported from soils, streams, or trees in the eastern USA and from Europe. Less complete inventories at least suggest that similar results will be obtained for temperate forests in Asia, South America, and South Africa [27][28][29][30]. The emerging story of a diverse assemblage and distinctive habitats is the same in Australia, although the species list is quite different [31][32][33].…”

Genotypic Diversity of Phytophthora cinnamomi and P. plurivora in Maryland’s Nurseries and Mid-Atlantic Forests

“…P. plurivora is one of eight species once considered part of the P. citricola complex (now delineated into P. capensis, P. caryae, P. citricola, P. pachypleura, P. pini, P. plurivora, P. multivora, and P. acerina) (Bezuidenhout et al 2010, Brazee et al in press, Ginetti et al 2014Henricot et al 2014;Hong et al 2011;Jung and Burgess 2009;Scott et al 2009). Although both species have a worldwide distribution, P. plurivora is potentially of Asian origin and introduced to North America from Europe (Huai et al 2013;Jung and Burgess 2009;Jung et al 2017;Schoebel et al 2014). P. cinnamomi is thought to have originated in Southeast Asia but became a globally well-established species in nursery, agricultural, and forest ecosystems, with records dating back over a century (Arentz and Simpson 1986;Balci et al 2007;Brasier et al 1993;Duan et al 2008;Erwin and Ribeiro 1996;Jung et al 2016Jung et al , 2017Zentmyer 1980).…”

“…The reason behind this pathological difference is likely related to its ecological adaptations. Unlike P. cinnamomi, P. plurivora is adapted to aquatic environments (e.g., fresh stream water or irrigation water), and can spread to aboveground plant parts through rain splash or overhead irrigation (Brazee et al 2016;Huai et al 2013;Jung et al 2016Jung et al , 2017Nechwatal et al 2011). Ecologically, P. plurivora appears to be not restricted by cold winter temperatures whereas P. cinnamomi is limited in its pathology and spread (Bergot et al 2004;McConnell and Balci 2014).…”