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

Thomas Jung,Thomas Cech,Gaetano Magnano Di San Lio,Santa Olga Cacciola,Diána Seress,József Bakonyi,Cristiana Maia,Salvatore Seddaiu,Bruno Scanu,Saveria Mosca,Antonella Pane,Alfredo Cravador,Marília Horta Jung,Antonio Franceschini,Leonardo Schena

doi:10.5598/imafungus.2017.08.02.02

Abstract

During surveys of Phytophthora diversity in natural and semi-natural Fagaceae forests in Austria, Italy and Portugal, four new cryptic species were isolated from rhizosphere soil samples. Multigene phylogeny based on nuclear ITS, ß-tubulin and HSP90 and mitochondrial cox1 and NADH1 gene sequences demonstrated that two species, P. tyrrhenica and P. vulcanica spp. nov, belong to phylogenetic Clade 7a, while the other two species, P. castanetorum and P. tubulina spp. nov, clustered together with P. quercina forming a new clade, named here as Clade 12. All four new species are homothallic and have low optimum and maximum temperatures for growth and very slow growth rates at their respective optimum temperature. They differed from each other and from related species by a unique combination of morphological characters, cardinal temperatures, and growth rates. Pathogenicity of all Phytophthora species to the root system of their respective host species was demonstrated in soil infestation trials.

Highlights

The family Fagaceae comprises about 1000 species belonging to eight to ten genera widely distributed across the Northern Hemisphere (Manos & Stanford 2001)
Multigene phylogeny based on nuclear internal transcribed spacer (ITS), ß-tubulin and heat shock protein 90 (HSP90) and mitochondrial cox1 and NADH1 gene sequences demonstrated that two species, P. tyrrhenica and P. vulcanica spp. nov., belong to phylogenetic Clade 7a, while the other two species, P. castanetorum and P. tubulina spp. nov., clustered together with P. quercina forming a new clade, named here as Clade 12
Several Phytophthora species, including P. cactorum, P. xcambivora, P. cinnamomi, P. plurivora, and P. quercina were strongly associated with the decline and dieback of forests, while other species, such as P. cryptogea, P. europaea, P. gallica, P. gonapodyides, P. megasperma, P. pseudosyringae, P. psychrophila, P. syringae, P. uliginosa, P. sp. forestsoil, and P. sp. riversoil, were more cryptic, and their role in forest ecosystems is still not fully understood

Summary

INTRODUCTION

The family Fagaceae comprises about 1000 species belonging to eight to ten genera widely distributed across the Northern Hemisphere (Manos & Stanford 2001). Besides species with wide geographical distributions and ecological amplitudes, such as sweet chestnut (Castanea sativa) and European beech (Fagus sylvatica), some evergreen oaks (e.g. Quercus ilex and Q. suber) are geographically restricted and adapted to particular environmental conditions such as prolonged VXPPHU GURXJKW DQG ¿UH 6FKLURQH et al 2016). Species in these genera constitute primarily forest resources LPSRUWDQW IRU WKHLU ZLGH UDQJH RI XVHV ELRPDVV ¿EUH ZRRG products, cork and food), they are keystone species in forest ecosystems and considered main drivers of terrestrial biodiversity (Kremer et al 2012). Pathogenicity of all new Phytophthora species against their respective hosts was tested in soil infestation trials WR FRQ¿UP .RFK¶V SRVWXODWHV

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Findings

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