Multi-gene sequence analysis and phenotypic diversity of Phaeoacremonium species isolated from grapevines in Spain

Abstract

Esca and Petri disease, caused by Phaeoa-cremonium, and other grapevine decline diseases, such as eutypa dieback, are responsible for serious economic losses to the wine industry worldwide. In the present work, 175 isolates of Phaeoacremonium spp. were collected (mostly in the region of Castilla y Leon, Spain) from vines either asymptomatic or symptomatic for grapevine decline diseases. The sequences of DNA fragments of 30 isolates were analysed. Amplicons of ITS, and partial gene of the β-tubulin, actin, calmodulin and translation elongation factor 1-α [EF1-α], were obtained by PCR. This is the first time that any exon of the EF1-α gene or exons 6–7 of the β-tubulin gene of seven Phaeoacremonium spp. have been amplified. Amplicons of the calmodulin and EF1-α exons were the most informative in terms of species differentiation: only 52.6 % and 56.6 % similarity across six and seven species was respectively seen. Phylogenetic analysis of combined DNA sequences revealed five Phaeoacremonium species isolated from the sampled plants; P. aleophilum was the most common. Four other species were found, however only one isolate each. P. mortoniae and P. iranianum are here reported for the first time on grapevines in the region of Castilla y Leon and the neighbouring region of La Rioja respectively. In total, 29 nucleotide differences among the studied gene fragments were seen across 23 isolates of P. aleophilum. Network analysis showed these Spanish P. aleophilum isolates to fall into two main groups of genotypes. P. aleophilum genotypes belonging to group 1 were mostly isolated from young grapevines affected by Petri disease but genotypes included in group 2 were isolated from adult plants showing esca or eutypa dieback symptoms.