TheEucalyptusstem canker pathogenTeratosphaeria zuluensisdetected in seed samples

The global spread of Eucalyptus pathogens is thought to be facilitated by the trade in seed for the establishment of new plantations and breeding programmes. In this study, we used high-throughput amplicon sequencing to elucidate whether this might be true for the Eucalyptus stem pathogen Teratosphaeria zuluensis in South Africa. DNA libraries were obtained for seed-capsules, clean seed, 1-month-old seedlings grown in a phytotron, plants grown in vitro in a tissue culture facility as well as leaves and stems of 3-month-old seedlings exposed to a Eucalyptus plantation environment. The DNA libraries were sequenced using high-throughput Illumina MiSeq and 454 technologies. Sequencing revealed the presence of several OTUs in the Botryosphaeriaceae, Mycosphaerellaceae and Teratosphaeriaceae in seed and seed-capsules and amongst these, OTUs that cluster close to T. zuluensis. OTUs from the Mycosphaerellaceae were also recovered from seedlings grown in a phytotron, in vitro propagated seedlings and those exposed to the plantation environment. The results support the view that important Eucalyptus pathogens, including T. zuluensis, can be spread via the trade in seed.