Pathogenicity of Phytophthora alni complex and P. plurivora in Alnus glutinosa seedlings

Abstract

Summary The ecological importance of riparian forests is well known. However, these forest habitats have been disturbed by human activities over the past century as a result of the introduction of flow regulations. Mortality of the riparian alder population caused by Phytophthora has become an important issue in Europe in the past two decades. The main objective of this study was to examine the pathogenicity of the Phytophthora alni complex (P. xalni, P. uniformis and P. xmultiformis) and P. plurivora in Alnus glutinosa seedlings. Phytophthora alni complex has traditionally been identified as the main causal agent of alder decline; however, in this study, P. plurivora was found to cause as much damage in inoculated seedlings as P. alni complex. In fact, Spanish isolates of P. xalni caused mortality rates of ca. 30%, whereas P. plurivora killed ca. 50% of seedlings. Likewise, there were no differences between P. xalni ‐ and P. plurivora‐inoculated seedlings in either the length of lesion or biomass allocation. The pathogenicity of the species within P. alni complex did not differ significantly. The findings confirm that P. plurivora, which is one of the most common species of Phytophthora found in European nurseries, is highly pathogenic to alder seedlings. Urgent implementation of measures to prevent the risk of spread of the pathogen from nurseries to natural ecosystems is required. Further studies are required to clarify the role that P. plurivora is playing in alder decline both individually and in combination with P. alni complex.

Phytophthora Species from Xinjiang Wild Apple Forests in China

“…plurivora from clade 2 is known to be a serious pathogen of many forest trees, including oak, beech, and Alnus glutinosa seedlings. This species can cause dieback and root loss and is most frequently associated with cankers in Europe, North America, and Asia [31][32][33][50][51][52][53][54][55]. Via the examination of plant tissues and soil samples, it has been reported to cause cankers in wild apple forests in Xinjiang [17], corroborating its discovery in stream water and soil samples in the present study.…”

Invasive forest pathogens affect the characteristics, microbial colonisation, and decomposition of leaf litter in streams

“…), highly susceptible to the oomycete Phytophthora ×alni Brasier & S. A. Kirk; and (3) U. minor , highly susceptible to the ascomycete Ophiostoma novo‐ulmi Brasier. These three pathosystems were selected as they are widespread and have resulted in extensive dieback and tree mortality in southern Europe (Alcaide et al., 2020; Ghelardini et al., 2017; Jung et al., 2018; Solla et al., 2010; Zamora‐Ballesteros et al., 2016).…”

Diversity and Pathogenicity of Phytophthora Species Associated with Declining Alder Trees in Italy and Description of Phytophthora alpina sp. nov

“…However, recent studies have demonstrated that other Phytophthora species are involved in the aetiology of alder decline. In particular, the plurivorous pathogen P. plurivora has recurrently been isolated from declining alders in different countries [13][14][15] and its pathogenicity towards alders has been demonstrated [15,16].…”