Physiological responses of cork oak and holm oak to infection by fungal pathogens involved in oak decline

Abstract

The aim of this research was to study the changes in net photosynthesis and stomatal conductance values in 3-year-old cork oak and holm oak seedlings growing in natural conditions and inoculated with Apiognomonia quercina, Biscogniauxia mediterranea, Botryosphaeria corticola and Pleurophoma cava. Throughout the 4-month experimental period, the evolution of visual external symptoms and the values of physiological variables were periodically recorded. All pathogens caused stem lesions around the infection point; however, the lesions caused by B. corticola were longer in both oak species. On cork oak seedlings, all pathogens induced a significant and gradual reduction in net photosynthesis and stomatal conductance values, whereas other physiological disturbances were induced only by B. corticola infections on holm oak seedlings

Resistance to Dutch Elm Disease Reduces Presence of Xylem Endophytic Fungi in Elms (Ulmus spp.)

“…Earlier, P. cava has been reported as an endophytic species involved in the aetiology of decline of Mediterranean Quercus trees [72], [73]. The fungus M. nivalis is a snow mold with a temperature minimum of −5°C for growth [74].…”

Emergent insects, pathogens and drought shape changing patterns in oak decline in North America and Europe

“…appear to be weak pathogens involved in oak decline; but those oaks infected may be less likely to survive defoliation (Marçais and Bréda, 2006). Other root pathogens have been shown to reduce rates of oak-seedling photosynthesis (Linaldeddu et al, 2009). Marçais et al (2011) found that inoculating seedlings with a combination of pathogens known to be associated with oak decline (C. fusipes, Armillaria mellea, and two Phytophthora spp.)…”

Endemic and Emerging Pathogens Threatening Cork Oak Trees: Management Options for Conserving a Unique Forest Ecosystem

“…Two species in particular, Diplodia corticola and Biscogniauxia mediterranea, were found to be the most widely distributed pathogens in declining cork oak forests; the first has been considered the most virulent cork oak pathogen (Linaldeddu et al 2009b;Luque et al 2000). Attacks of D. corticola, originally misidentified as Diplodia mutila, were reported on cork oak trees in Italy, Morocco, Portugal, Spain, and Tunisia (Alves et al 2004).…”

“…On cork oak, D. quercina causes dark brown-toblack leaf spots, coalescing into larger necrotic areas at the end of the growing season; sometimes it also causes twig cankers. At the physiological level, infection of D. quercina on cork oak modifies the normal balance of some metabolic processes, including stomatal conductance and photosynthesis (Linaldeddu et al 2009b). D. quercina has been shown to produce in vitro several secondary bioactive metabolites, some of which are phytotoxic (Maddau et al 2011).…”