Quercirhiza quadratum: a revision of the characters and identity of the ad type ectomycorrhiza

Abstract

The well-known AD type, described first by Giraud in 1988, is considered as a competitor in black truffle (Tuber melanosporum Vittad.) plantations. It has been mainly observed in T. melanosporum and T. magnatum Pico plantations in France and Italy. This ectomycorrhiza has always been observed on roots of oak (Quercus ilex L. and Q. faginea Lam.) and hazelnut (Corylus avellana L.) plantations with “burnt” areas around the trees, even in those that do not produce black truffle sporocarps, so it can create false expectations in young plantations. The AD type has also been described in nurseries, as a competitive ectomycorrhiza on seedlings inoculated with black truffle. In Spain, AD type has been detected in black truffle plantations and natural holm oak stands in Navarra, Soria, Huesca, Zaragoza, Teruel, Castellón and Valencia. In 2005, De Román & De Miguel, suggested that AD type could be a telephoroid type due to its anatomical and morphological characters. In 2006, Baciarelli-Falini et al. using molecular techniques identified this type as an Ascomycotina belonging to Pezizales. The detailed anatomical, morphological and molecular study of the AD type led to a description as Quercirhiza quadratum (Águeda et al. 2008). Based on the anatomical and morphological characters, the AD type belongs to the Ascomycotina. The presence of Woronin bodies on hyphal septa, and the sometimes slightly dissolved septa, are two typical characters of this group. The DNA sequences obtained from the AD types studied showed close similarities with members of Pyronemataceae and Sarcosomataceae (Pezizales). Both taxonomic groups correspond to the same AD type as found by Baciarelli Falini et al., (2006). One of the studied sequences showed a close identity (100% maximum identity, 84% coverage) with Trichophaea woolhopeia (Cooke & W. Phillips) Arnould, although records of this fungal species are scarce in the Iberian Peninsula.