Previously unrecorded low‐temperature Phytophthora species associated with Quercus decline in a Mediterranean forest in eastern Spain

Abstract

Oak decline has been a serious problem in Europe since the beginning of the twentieth century. In south-west Spain, Quercus ilex and Q. suber are the main affected species, and their decline has been associated with Phytophthora cinnamomi. During the last 10 years, a severe decline of Q. ilex and Q. faginea accompanied by a significant decrease in the production of acorns affecting natural regeneration was observed in the eastern part of the Iberian Peninsula. Therefore, the aim of this study was to investigate the possible involvement of Phytophthora spp. in the decline. A forest in the Natural Park 'Carrascar de la Font Roja' in Comunidad Valenciana (eastern Spain), which is dominated by Q. ilex and Q. faginea, was surveyed during 2010-2011. Symptomatic trees showed thinning and dieback of the crown, withering of leaves and death. An extensive loss of both lateral small woody roots and fine roots and callusing or open cankers on suberized roots were observed. Soil samples containing fine roots were baited using both Q. robur leaves and apple fruits. Six Phytophthora species were isolated: P. cryptogea, P. gonapodyides, P. megasperma, P. quercina, P. psychrophila and P. syringae. These are the first records of P. quercina and P. psychrophila on Q. faginea, of P. quercina in Spain and of P. psychrophila in mainland Spain. A soil infestation trial was conducted for 6 months under controlled conditions with 1-year-old seedlings of Q. ilex and Q. faginea. Phytophthora cinnamomi was included in the pathogenicity test for comparison. The results showed that Q. ilex seedlings were generally more susceptible to infection than Q. faginea with P. cinnamomi being the most aggressive pathogen to both oak species. The two most commonly isolated Phytophthora species, P. quercina and P. psychrophila, also proved their pathogenicity towards both Q. ilex and Q. faginea.

Multiple new cryptic pathogenic Phytophthora species from Fagaceae forests in Austria, Italy and Portugal

“…This is similar to that of other possibly endemic low-temperature Phytophthora species such as P. ilicis , P. pseudosyringae , P. psychrophila, and P. quercina (Jung et al 1999, 2002, Pérez-Sierra et al 2013, Scanu et al 2014b, Scanu & Webber 2016). All four new species are homothallic, with a high oospore wall index (range 0.4–0.5) enabling them to survive both the long hot and dry summers typical of Mediterranean regions ( P. castanetorum , P. tyrrhenica, and P. vulcanica ) and cold winters in Austria ( P. tubulina ), on Mount Etna ( P. vulcanica ), and in the Gennargentu Mountain and Serra da Estrela ( P. castanetorum ).…”

“…Phytophthora quercina is involved in decline syndromes of natural and planted Quercus stands ( Q. cerris , Q. coccinea , Q. faginea , Q. ilex , Q. palustris , Q. petraea , Q. pubescens , Q. pyrenaica , Q. robur , Q. rubra , Q. suber , and Q. vulcanica ) across Europe causing a progressive destruction of fine root systems, which predisposes affected oaks to climatic extremes and secondary pathogens and pests (Jung et al 1999, 2000, 2013, 2016, Balci & Halmschlager 2003a, b, Perez-Sierra et al 2013). Interestingly, P .…”

“…Since the early 1990s, numerous surveys in declining and healthy European Fagaceae forests have revealed a wealth of resident Phytophthora species (Jung 2009, Perez-Sierra et al 2013, Scanu et al . 2013).…”

Drought-induced oak decline in the western Mediterranean region: an overview on current evidences, mechanisms and management options to improve forest resilience

“…During the last decades, several defoliating insects species have been reported among the main mortality agents of oak forests, particularly in Northern America (see Haavik et al 2015 for a review). The pathogens associated with the oak decline in Mediterranean areas are generally recognizable as secondary biotic factors (i.e., due to opportunistic organisms that develop as a consequence of the loss in tree vigor), such as root fungi of the Armillaria and Phytophthora genera (De Sampaio et al 2013, Vettraino et al 2002, Perez-Sierra et al 2013, and stem cankers caused by Hypoxylon spp. Within these studies a large variability of symptoms is reported (i.e., foliage rarefaction and wilting, drying of branches, crown dieback, delay of spring bud burst, production of epicormic shoots, longitudinal cracks of the bark which is often detached, reduction of biomass, necrotic lesions and necrosis of absorbing roots - Fig.…”

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

“…Other Phytophthora species, namely P. quercina, P. gonapodyides, and P. psychrophila, have been recently associated with declining Mediterranean oaks in Italy and Spain and their pathogenicity has been demonstrated on Quercus faginea, Q. ilex, and Q. suber Pérez-Sierra et al 2013;Seddaiu et al 2014).…”