Chestnut blight cankers caused by the fungal pathogen Cryphonectria parasitica on infected American chestnut trees can be invaded by hypoviruses that infect C. parasitica mycelia. Hypoviruses lower pathogen virulence (i.e. hypovirulence) and decrease the probability of stem girdling. Cankers also are susceptible to invasion by non-C. parasitica fungi; however, the influence of invading fungi on disease severity is unknown. Fungi may antagonize C. parasitica growth and combine with hypovirulence to further reduce the probability of stem girdling. We conducted a survey to investigate how spatial and temporal dynamics of the fungal community within cankers correlate with canker severity and the likelihood of girdling. Cankers from six American chestnut populations were monitored from 2012 to 2016. We found that the spatial distribution of the fungal community within a canker resembled a mosaic that increased in fungal diversity over time. Cankers with increased fungal diversity were not associated with higher stem survivorship over time, compared to cankers with abundant hypovirulence in recovering chestnut populations. Fungal communities also were unstable, and cankers on surviving trees containing hypovirulence consistently were invaded by non-C. parasitica fungi. Our results suggest that canker communities are not stable, and volatility of the fungal community indicates that cankers can change quickly from less severe to more severe cankers through loss of hypovirulence. Non-C. parasitica fungi may facilitate canker expansion through greater inhibition of hypovirulent C. parasitica relative to virulent C. parasitica, which may permit virulent C. parasitica to escape hypovirus infection and resume rapid canker expansion.

在被感染的美国栗树上，由真菌病原体寄生寄生虫（Cryphonectria parasitica）引起的栗枯萎病可以被感染寄生寄生衣原体菌丝体的次病毒感染。次病毒降低了病原体的毒性（即低毒力）并降低了茎环的可能性。溃疡病也容易被非寄生寄生梭状芽孢杆菌的真菌侵袭。但是，入侵真菌对疾病严重性的影响尚不清楚。真菌可能拮抗寄生虫衣原体生长，并与低毒力相结合，以进一步减少茎环脱的可能性。我们进行了一项调查，以调查溃疡病患者体内真菌群落的时空动态如何与溃疡病患者的严重程度和环剥的可能性相关。从2012年到2016年，对六个美洲板栗种群的溃疡病进行了监测。我们发现，溃疡病中真菌群落的空间分布类似于马赛克，随着时间的推移真菌的多样性增加。与恢复栗子种群中低毒力丰富的溃疡病相比，真菌多样性增加的溃疡病患者随着时间的推移没有更高的茎存活率。真菌群落也不稳定，含有低毒力的幸存树木上的溃疡病一直受到非寄生虫C.的侵袭。菌类。我们的结果表明，溃疡病菌群落不稳定，真菌群落的挥发性表明，溃疡病菌可以通过丧失低毒力而迅速从较不严重的溃疡病菌转变为较严重的溃疡病菌。相对于强毒的寄生性丙酸杆菌，非寄生性丙酸杆菌真菌可以通过更大程度地抑制低毒的寄生性丙酸杆菌来促进溃疡病扩展，这可以使强毒的寄生性丙酸杆菌摆脱低病毒感染并恢复快速的溃疡病扩展。