Depotter Jasper R L, Rodriguez-Moreno Luis, Thomma Bart P H J, Wood Thomas A
First, second, and third authors: Laboratory of Phytopathology, Wageningen University and Research, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands; and first and fourth authors: Department of Crops and Agronomy, National Institute of Agricultural Botany, Huntingdon Road, CB3 0LE Cambridge, United Kingdom.
Phytopathology. 2017 Nov;107(11):1399-1405. doi: 10.1094/PHYTO-05-17-0184-R. Epub 2017 Aug 28.
Verticillium longisporum is an economically important fungal pathogen of brassicaceous crops that originated from at least three hybridization events between different Verticillium spp., leading to the hybrid lineages A1/D1, A1/D2, and A1/D3. Isolates of lineage A1/D1 generally cause stem striping on oilseed rape (Brassica napus), which has recently been reported for the first time to occur in the United Kingdom. Intriguingly, the emerging U.K. population is distinct from the north-central European stem striping population. Little is known about the pathogenicity of the newly emerged U.K. population; hence, pathogenicity tests were executed to compare British isolates to previously characterized reference strains. In addition to the model plant Arabidopsis thaliana, the pathogenicity of four British isolates was assessed on four cultivars of three Brassica crop species: oilseed rape (Quartz and Incentive), cauliflower (Clapton), and Chinese cabbage (Hilton). To this end, vascular discoloration of the roots, plant biomass accumulations, and fungal stem colonization upon isolate infection were evaluated. The British isolates appeared to be remarkably aggressive, because plant biomass was significantly affected and severe vascular discoloration was observed. The British isolates were successful stem colonizers and the extent of fungal colonization negatively correlated with plant biomass of cauliflower and Quartz oilseed rape. However, in Quartz, the fungal colonization of A1/D1 isolates was significantly lower than that of the virulent reference isolate from lineage A1/D3, PD589. Moreover, despite levels of stem colonization similar to those of A1/D1 strains, PD589 did not cause significant disease on Incentive. Thus, A1/D1 isolates, including British isolates, are aggressive oilseed rape pathogens despite limited colonization levels in comparison with a virulent A1/D3 isolate.
长孢轮枝菌是十字花科作物的一种具有重要经济意义的真菌病原体，它起源于不同轮枝菌属之间至少三次杂交事件，产生了杂交谱系A1/D1、A1/D2和A1/D3。A1/D1谱系的分离株通常会导致油菜（甘蓝型油菜）出现茎条斑，最近英国首次报道了这种情况。有趣的是，新出现的英国种群与欧洲中北部的茎条斑种群不同。对于新出现的英国种群的致病性知之甚少；因此，进行了致病性测试，以将英国分离株与先前鉴定的参考菌株进行比较。除了模式植物拟南芥外，还对三种十字花科作物的四个品种评估了四个英国分离株的致病性：油菜（石英和激励品种）、花椰菜（克拉普顿品种）和大白菜（希尔顿品种）。为此，评估了分离株感染后根部的维管束变色、植物生物量积累以及真菌在茎中的定殖情况。英国分离株似乎具有很强的侵染性，因为植物生物量受到了显著影响，并且观察到了严重的维管束变色。英国分离株能够成功地在茎中定殖，并且真菌定殖程度与花椰菜和石英油菜的植物生物量呈负相关。然而，在石英油菜中，A1/D1分离株的真菌定殖显著低于来自A1/D3谱系的强毒参考分离株PD589。此外，尽管PD589在茎中的定殖水平与A1/D1菌株相似，但它在激励品种上并未引起明显病害。因此，包括英国分离株在内的A1/D1分离株是具有侵染性的油菜病原体，尽管与强毒的A1/D3分离株相比定殖水平有限。
