Abstract: The first Périgord black truffle (PBT, Tuber melanosporum) recorded in the Southern Hemisphere was produced in New Zealand in 1993 at a plantation established in 1988 . Today, there are over 100 PBT plantations in New Zealand. Of these, ten are currently fruiting with many more expected to start in the next few years . In 2005 a research project co-funded by the New Zealand Truffle Association and the New Zealand government was launched with the aim of improving our understanding of the effects of the soil moisture and aeration on fruiting of PBT. In order to ensure that trees selected for the trial had PBT mycorrhizae on their roots , we first sampled roots from the northern side of randomly selected trees at three PBT plantations. The diagnosis of PBT mycorrhiza was performed using
morphological (microscopy) and molecular ( specific PCR primers for the rDNA ITS) analyses . On one plantation , trees showed a very high level of PBT mycorrhization and a low level of contamination , therefore identifying 16 trees with PBT mycorrhizae from this site was an easy task. For the other 2 plantations, we randomly sampled up to 34 trees in order to find 16 trial trees at each site unequivocally mycorrhized by PBT. Our strategy to sample roots on the northern side of the trees was supported by the analyses of several trees sampled around all four aspects (North , South , East , West) , which confirmed that mycorrhizae were always present on the northern side of the tree root systems . Following tree selection, a number of treatments have been applied to test the hypothesis that soil aeration and soil moisture are important soil factors that affect mycorrhization and fruiting . Preliminary results showed that the irrigation treatment slightly reduced soil temperature
around the roots of mycorrhized trial trees . Since 2006 the New Zealand Institute for Crop and Food Research (C & FR) 1 has also performed over 140 root analyses from PBT plantations situated throughout New Zealand . From this extensive root survey we have obtained valuable insights into: (1) the persistence of PBT mycorrhizae on planted trees; (2) the presence of other competing ectomycorrhizal fungi ; and (3) the presence of an unexpected truffle , Tuber brumale, which has been found in very few plantations but , to our knowledge, has not fruited yet in New Zealand. Recently, fruiting of two other valuable truffle species has been reported for the first time in New Zealand plantations:Tuber borchii in 2006 and Tuber uncinatum ( syn . T. aestivum) in 2007 .

Key words: Truffle cultivationl