The diversity of Eutypa lata was studied in 56 isolates collected from Languedoc-Roussillon, France. The pathogenicity of isolates
varied within a very broad range and was not influenced by the cultivar from which they originated. Using 27 RAPD markers, each
isolate was identified as an unique genotype. Gene diversity averaged 0·292 for the regional population. Lack of gametic
disequilibrium between RAPD loci supported the hypothesis of random mating. The RAPD analysis did not allow subdivision of the
population according to geographic location, vine cv. or pathogenicity of E. lata. The composition of the community of fungi was
studied in 116 vines showing eutypa dieback symptoms collected at several localities in the region. E. lata was recovered from 80%
of the samples, from the sectorial brown lesion characteristic of the disease. This lesion was associated in half of the vines with a
central zone of discoloured hard wood and/or a light-coloured lesion of soft consistency. E. lata was isolated alone from 124% of
the vines and was associated in 67% of the vines with one, two or three of the following fungi: Sphaeropsis malorum, Phomopsis
viticola, Gliocladium roseum, Phaeoacremonium chlamydosporum, P. aleophilum and Phellinus igniarius. The variation in symptoms
observed in the vineyard may be partly explained by the wide genetic diversity in E. lata and differences in the composition and
functioning of the fungal community.