Effect of azoxystrobin on tobacco leaf microbial composition and diversity.

Azoxystrobin, a quinone outside inhibitor fungicide, reduced tobacco target spot caused by by 62%, but also affected the composition and diversity of other microbes on the surface and interior of treated tobacco leaves. High-throughput sequencing showed that the dominant bacteria prior to azoxystrobin treatment were on healthy leaves and on diseased leaves, and the dominant fungi were (teleomorph of ) and on healthy leaves and on diseased leaves. Both bacterial and fungal diversity significantly increased 1 to 18 days post treatment (dpt) with azoxystrobin for healthy and diseased leaves. For bacteria on healthy leaves, the relative abundance of , and declined, while and increased. On diseased leaves, the relative abundance of and declined, while and increased. For fungi on healthy leaves, the relative abundance of declined, while , , , and increased. On diseased leaves, the relative abundance of declined, while , , , , , and , increased. Compared to healthy leaves, azoxystrobin treatment of diseased leaves resulted in greater reductions in , and , a greater increase in , and similar changes in , and . Azoxystrobin had a semi-selective effect altering the microbial diversity of the tobacco leaf microbiome, which could be due to factors, such as differences among bacterial and fungal species in sensitivity to quinone outside inhibitors, ability to use nutrients and niches as certain microbes are affected, and metabolic responses to azoxystrobin.