Most asexual species of fungi have either lost sexuality recently, or they experience recombination by cryptic sexual reproduction. Verticillium dahliae is a plant-pathogenic, ascomycete fungus with no known sexual stage, even though related genera have well-described sexual reproduction. V. dahliae reproduces mitotically and its population structure is highly clonal. However, previously described discrepancies in phylogenetic relationships among clonal lineages may be explained more parsimoniously by recombination than mutation; therefore, we looked for evidence of recombination within and between clonal lineages. Genotyping by sequencing was performed on 141 V. dahliae isolates from diverse geographic and host origins, resulting in 26,748 single-nucleotide polymorphisms (SNPs). We found a strongly clonal population structure with the same lineages as described previously by vegetative compatibility groups (VCGs) and molecular markers. We detected 443 recombination events, evenly distributed throughout the genome. Most recombination events detected were between clonal lineages, with relatively few recombinant haplotypes detected within lineages. The only three isolates with mating type MAT1-1 had recombinant SNP haplotypes; all other isolates had mating type MAT1-2. We found homologs of eight meiosis-specific genes in the V. dahliae genome, all with conserved or partially conserved protein domains. The extent of recombination and molecular signs of sex in (mating-type and meiosis-specific genes) suggest that V. dahliae clonal lineages arose by recombination, even though the current population structure is markedly clonal. Moreover, the detection of new lineages may be evidence that sexual reproduction has occurred recently and may potentially occur under some circumstances. We speculate that the current clonal population structure, despite the sexual origin of lineages, has arisen, in part, as a consequence of agriculture and selection for adaptation to agricultural cropping systems.

Artículo open access.Olive trees (Olea europaea (L.) subsp. europaea\ud (L.)) were among the first fruit trees cultivated and are among the most ancient crops in the Mediterranean Basin. Cultivated olive trees can be distin-\ud guished from their wild relatives by larger\ud fruits and higher oil content of the fleshy\ud oil-containing mesocarp. The edible oil\ud and fruit products of cultivated olive trees\ud are prized worldwide.Original results from the authors reported in this\ud article were derived from research supported by\ud grants (AGR-136, AGL2008-00344, and P08-AGR-\ud 03528)\ud from Dirección General de Investigación,\ud Ministerio de Ciencia e Innovación, Spain and\ud Consejería de Innovación Ciencia y Empresa, Junta\ud de Andalucía, Spain.Peer reviewe