Wood Decay Measurement of Shiitake Cultivation Logs Based on Spin Relaxation Times Obtained using Magnetic Resonance Imaging

Abstract

Abstract To harvest large shiitake mushrooms (Lentinula edodes), it is important to adjust the suitable cultivation environment for shiitake mycelium so that it can extend throughout an entire log, maximizing wood decomposition and nutrient absorption. We attempted to measure the degree of wood decay of cultivation logs noninvasively by Magnetic Resonance Imaging (MRI). The cultivation logs were sourced from konara oak (Quercus serrata), which was inoculated with shiitake mycelium for 0.6 to 4 years. After MRI measurements, the logs were cut into wood pieces between 1 to 2 cm in length, and the degree of wood decay of the individual pieces was evaluated using the dry wood density. NMR signals were measured using a long echo time, TE = 11 ms, to obtain T1 and T2 relaxation times of free water in the logs. The results showed that wood decay of the cultivation logs correlated well with T2 values and poorly with T1 values. In addition, based on the obtained T2 map, the spatial distribution of wood decay within cultivation logs 1.6 years after inoculation could be visualized.