LB 9-82 - Comparison of Illumina high-throughput sequencing and classic isolation methods for determining decay risk and fungal communities within hardwood logs during air-seasoning.

While high throughput sequencing (HTS) continues to provide insights into fungal communities, there are specific situations where HTS should be evaluated against more traditional techniques. For example, fungal culture-isolates remain the primary means of predicting decay in wood for utility service. In this study we compared fungal communities by Illumina sequencing of fungal ITS sequences and by 325 basidiomycete cultures isolated from the same samples. We hoped to compare how each method informed decay risk among air-seasoning timbers intended for use as rail-ties. All samples were taken from the same 550 wood-cores extracted from 196 air-seasoning red oak or blackgum logs over 3 sampling times. These logs were air dried and subsequently evaluated for decay and strength-loss by destructive testing, which allowed for a unique comparison between methods of community detection.By pairing fungal identities with FunGuild we were also able to characterize the decay potential within larger communities, as well as describe successional trajectory in terms of trophic guilds. We also gained several insights into early-decay community succession that differed between different hardwoods under the same storage conditions. We anticipated blackgum and red oak logs to have different fungal communities at the time of their harvest, which would converge over time because of their same location and storage methods. Instead, we found that decay communities progressed in different directions, and over the span of a year became more disparate, both in HTS and in cultured isolates. Fungal communities indicated by HTS in red oak saw a continuing decrease in decay-related diversity, while neighboring communities in blackgum saw increasing numbers of decay-related species. From isolates we observed an increasing frequency of decay-related fungi in both hardwoods, but with different isolates from each.We identified 647 genera from HTS sequences, and only 165 genera by cultural isolates, but matched samples of HTS were only able to capture the same isolated fungus 62% of the time. By revealing only the most active community aspects and avoiding genetic artifacts, the culture based methods were more capable of relating fungi to decay risk, though the test was completed prior to severe decay occurring. A longer view of succession may yet reveal greater predictive power of either method towards final decay hazards. Also, while HTS should not currently be viewed as a replacement to determine decay risks, it greatly enhanced the understanding of decay as a dynamic community function.