Balancing the scales: Impact of irrigation and pathogen burden on potato blackleg disease and soil microbial communities

Abstract

AbstractUnderstanding the interaction between environmental conditions, crop yields, and soil health is crucial for sustainable agriculture in a changing climate. Management practices to limit disease are a balancing act. For example, in potato production, dry conditions favour common scab (Streptomycesspp.) and wet conditions favour blackleg disease (Pectobacteriumspp.). The exact mechanisms involved and how these link to changes in the soil microbiome is unclear. Our objectives were to test how irrigation management and bacterial pathogen load in potato seed stocks impact: i) crop yields; ii) disease development (blackleg/common scab); and iii) soil microbial community dynamics. We used stocks of seed potatoes with varyingPectobacteriumlevels (Jelly [high load], Jelly [low load], and Estima [Zero – noPectobacterium]). Stocks were grown under four irrigation regimes that differed in the timing and level of watering. The soil microbial communities were profiled using amplicon sequencing at 50% plant emergence and harvest and advanced bioinformatic analyses were used to correlate microbes to treatments and disease symptoms. Irrigation increased blackleg symptoms in the plots planted with stocks with low and high levels ofPectobacterium(22-34%) but not in the zero stock (2-6%). Not irrigating increased common scab symptoms (2-5%) and reduced crop yields. Irrigation did not impact the composition of the soil microbiome, but planting stock with a highPectobacteriumburden resulted in an increased abundance ofPlanctomycetota,Anaerolinea, andAcidobacteriaspecies within the microbiome. Ensemble quotient analysis highlightedAnaerolineaas highly associated with blackleg symptoms in the field. We conclude thatPectobacteriumpathogen load within seed stocks could have more substantial effects on soil communities than irrigation regimes.