Neonectria ditissima isolate:RS 305p Genome sequencing and assembly. Neonectria ditissima isolate:RS 305p

Neonectria ditissima is a fungal pathogen causing canker disease in many broad-leaved tree species. In terms of horticultural species, it is a threat to the apple and pear industry where it causes the disease European canker. Early symptoms of the disease in spring are characterised by flaking bark on infected shoots and spurs. These lesions develop into cankers with white sporodochia and, in autumn and winter, red perithecia. Cankers can girdle entire trunks or tree limbs causing death of tissue beyond the canker. The disease is most severe in mild, wet climates. Apple canker is currently controlled by judicious pruning and by fungicides. Different apple varieties show varying susceptibilities to canker, hinting at the possibility of breeding a highly tolerant or resistant cultivar. Variation is also seen in the pathogen population. Firstly at the level of host range determination; formae speciales probably exist within N. ditissima sensu lato with different isolates able to infect certain host species but not others, and secondly, variation in virulence is seen within the populations of N. ditissima able to infect apple. Thus two single-ascospore isolates of N. ditissima were selected for whole genome sequencing: RS 305p, isolated from M. x domestica cv ‘Brookfield’, South Island, New Zealand, low virulence; and RS 324p, isolated from M. x domestica cv ‘Golden Delicious’, North Island, New Zealand, high virulence. In addition to their different virulences, these isolates are of opposite mating type enabling future crossing and mapping experiments. Comparative genomics of isolates varying in virulence against apple may provide details on how the pathogen can infect and which pathogenicity determinants are essential for virulence and pathogen fitness.