Le chêne blanc et le chêne vert, essences truffières par excellence

Truffies grow in association with a num­ ber of deciduous and coniferous tree spe­ cies. However, not ail of these species offer the same interest for the cultivation of top quality truffles. The oaks (Quercus ssp) feature among the best symbiotic hosts for the truffle, as muchfor the longevity ofproduction asfor the quality of the truffles obtained. Downy oak (Q. pubescens) and holm oak (Q. ilex) are the truffle trees of the Périgord par excellence (T. de Tricastin, T. de Noria and Spoletto, T. melanospo­ rum ) , because they are the best adapted to the particular conditions of soil and clima­ te in which the mushroom develops. Furthermore, the morphology of their root system and their slow rate of growth facili­ tate optimal development of the mushroom in the soil. The downy oak - thermophilic, heliophi­ Lous, xerophilous to mesoxerophilous, hardy, lime- resistant - is adapted above alt to the production of the truffle of Périgord but is also suitable of obtaining other varieties of fine truffles, including the celebrated piedmont white truffle (T. magnatum). The holm oak, heliophilous, thermoxero­ philo us, hardy, with a wide range of habi­ tat is adapted above all to the production of the truffle of Périgord and the summer truffle (T. aesti vum ). Since 1973, sorne 850,000 downy and holm oaks and 250,000 hazels, innoculated with truffle mycorrhiza under the supervi­ sion of the INRA (French national agricul­ tural research body), have been planted in numerous areas in the south of France and even in the north. Studies have shown the superiority of the oak over the hazel, parti­ cularly with regard to the frequency and regularity of production. In respect to rapidity of coming into production, sorne holm oaks were as early as hazels (three and a halfyears after planting). Mycorrhiza-innoculated plants presently available appear, wh en planted, as very heterogenious (aspect, habit, yield) due to the fact that they are multiplied by sowing. Selecting of vegetatively reproduced plants is currently under way. One study is inves­ tigating whether in a "good producer" there exists a relationship between yield and certain ofils genetic characteristics.