Variation of endophytic cork oak-associated fungal communities in relation to plant health and water stress

Abstract

SummaryThe main objective of this study was to obtain more comprehensive knowledge about the effect of water stress on endophytic fungal communities in asymptomatic and declining cork oak trees. Six asymptomatic and six declining cork oak trees were randomly selected in a natural cork oak forest located in Sardinia, Italy. In February 2003, the soil around three asymptomatic and three declining trees was covered with a circular plastic film to reduce rain water supply with the intention to induce water stress. The remaining six trees served as controls. Predawn xylematic water potential (PWP) was used as water status indicator and measured seasonally. Between July 2003 and June 2004, fungal endophytes were isolated every 2-4 months from twigs, branches and woody tissues. Significant differences in PWP between covered and control trees were detected mainly in autumn. Gas exchange was greatest in asymptomatic control plants. All tissues were colonized by endophytic fungi. Nineteen fungal species were isolated from 1620 plant fragments. Biscogniauxia mediterranea was the most frequently isolated fungus. Its isolation frequency was significantly higher in declining covered trees than in control trees (p < 0.05). Presence of this fungus in asymptomatic control trees was significantly higher in winter than in summer. Water stress seems to reduce species diversity of the endophytic mycobiota in cork oak and to promote proliferation of some potentially pathogenic endophytes.

Fungal endophytic communities on twigs of fast and slow growing Scots pine ( Pinus sylvestris L.) in northern Spain

“…Black circles and abbreviated names in italics represented fungal species (Table 3) had been taken, but in this context the dominant and abundantly occurring species are of greatest interest because they are more likely to be host-specialists (Saikkonen 2007). Even if half of the actual species remained undetected we can assume to have encountered most dominant species culturable on PDA because the majority of fungal species in healthy trees of natural environments generally occur at very low numbers and just a few are frequent (M€ uller & Hallaksela 1998;Ragazzi et al 2003;Saikkonen 2007;Linaldeddu et al 2010). The isolation method used in this study favours medium and fast growing fungi, and thus, some of the slow growing species may have remained undetected, as well as all species not culturable on PDA.…”

Diplodia corticola and Phytophthora cinnamomi: the main pathogens involved in holm oak decline on Caprera Island (Italy)

“…; Ragazzi ; Linaldeddu et al. ). In the acute form, affected trees develop decline symptoms quite suddenly and high levels of mortality occur (Camilo‐Alves et al.…”

Growth and physiological responses of Quercus brantii seedlings inoculated with Biscogniauxia mediterranea and Obolarina persica under drought stress

“…Moreover, after 3 months of stress, xylem water potential did not change under the impact of pathogens and well-watered seedlings, but it decreased under the combination of pathogen inoculation and drought. In this respect, B. mediterranea spread at a high rate when water potential is reduced (Capretti & Battisti, 2007;Linaldeddu et al, 2011;Vannini et al, 2009). Reduced water potential of plants under drought is a common physiological response to perform osmo-regulation and maintain plant water to enhance drought resistance (Ranjbarfordoei, Vandamme, & Samson, 2013) occurring in different studies on different species of oak (Aranda, Castro, Pardos, Gil, & Pardos, 2005;Capretti & Battisti, 2007;Cotrozzi et al, 2016).…”