Wood decay in poplar trees for biomass production.

A rapid decay of Poplars AF2 clone, Populus x canadiensis, selected for biomass production addressed to produce energy and with an elevated tolerance to several harshnesses, has been observed in year 2013 in three fields (41.5ha) in Bologna Province. These fields were set in March 2010, pruning in two of the three fields was not done at the due time, since plants showed a scarce growth, with an incidence over 80%. Observations and samplings were done on plants of plots (10x10m) of each field. Trunk cross sections of all tested plants showed a central area, at 8cm from the soil, completely necrotic surrounded by a typical reddish ring extended up to 60%. Fungal colonies with fluffy grey mycelium were isolated from woody fragments, plated on agar medium. Their identification through sequencing of partial rDNA ITS region was performed comparing sequences in the NCBI database by BLASTn search algorithm. The nucleotide search comparison showed 98% identity with Cryptosphaeria lignyota (Fr.) Auersw. This fungus has been reported in literature as responsible of wood decay of some plant species, i.e. genus Populus and especially those with rapid growth. It can kill young trees within a year from infection and contributes to natural thinning of trunk formations. It seems that the host death might be due to massive invasion of the sapwood, that prevents it from transporting water and nutrients, and not to annular extension of the canker. The fungus is responsible of a great economic loss being all the infected plants highly compromised.