Genomic sequencing indicates non‐random mating of Venturia inaequalis in a mixed cultivar orchard. (11th February 2020)

• Record Type: Journal Article
• Authors: Passey, Thomas A. J.; Armitage, Andrew D.; Sobczyk, Maria K.; Shaw, Michael W.; Xu, Xiangming
• Is Part Of: Plant pathology. Volume 69:Number 4(2020)
• Page Start: 669
• Page End: 676
• Publication Date: 2020-02-11
• Subjects: apple black spot -- apple scab -- ascospore production -- host mixture -- super‐race; Agricultural pests -- Periodicals; Plant diseases -- Periodicals; 632
• DOI: 10.1111/ppa.13150
• Languages: English
• ISSNs: 0032-0862

Abstract

Abstract: Apple scab is one of the most economically important diseases of apples worldwide. The disease is caused by the haploid ascomycete Venturia inaequalis . Growing apples in cultivar mixtures may reduce disease severity. To determine how the pathogen population structure is affected by host mixtures we studied 24 V. inaequalis isolates sampled from three different apple cultivars (Bramley, Cox, and Worcester) growing in a mixed orchard approximately 50 years old. The isolates were aligned against a reference genome and single nucleotide polymorphisms (SNPs) were called between the isolates. The populations isolated from Bramley and Worcester were distinct, while Cox isolates were an admixture. This supports previous tests of the ability of isolates to cross‐infect hosts, and molecular comparisons using simple sequence repeats (SSRs). Genotype‐specific allele (GSA) loci were not distributed randomly across contigs in proportion to contig length, but were clustered. Clustered GSA loci were observed in almost all contigs. This indicates population differentiation across the whole genome, presumably due to lack of crossing‐over events between Bramley and Worcester isolates. This lack is probably due to physical separation effects: sexual mating is more likely to take place and succeed between isolates from lesions on the same leaf than from contact between independently infected leaves in leaf litter on the orchard floor. This would especially be the case if sexual reproduction is initiated before leaf‐fall. Abstract : Sexual mating in Venturia inaequalis is more likely to take place and succeed between isolates from lesions on the same leaf than from contact between independently infected leaves in leaf litter on the orchard floor.