Water concentration and rate of decrease in shiitake cultivation log during fruiting body development, as measured by MRI.

Large shiitake mushrooms (Lentinula edodes, pileus > 8 cm in diameter) are difficult to cultivate and account for only 3-5% of the total harvest. This study focused on the water absorption process within a log during the growth of fruiting bodies in order to increase the yield of large shiitake mushrooms. Konara oak logs (Quercus serrata, 85-95 mm in diameter, 290 mm in length) were inoculated with shiitake mycelium plugs and nine months later, young fruiting bodies developed, at which point the log was analyzed using magnetic resonance imaging (MRI) over a period of two weeks. The signal intensity and T1 and T2 relaxation time constants were determined from the acquired images, along with the distribution of water concentration within the entire log. The axial distributions of water concentrations in the log were higher in the 80 mm region around the fruiting body. The rate of decrease in water concentration indicated that water was supplied to the fruiting body from 80 mm axially in the upper half of the sapwood in the log. On the other hand, the water concentration in the heartwood did not decrease and the heartwood did not contribute to the water supply to the fruiting bodies.

Enhanced water uptake in the longitudinal direction by shiitake mycelium in shiitake cultivation logs: water content distribution in logs measured by magnetic resonance imaging.

In the cultivation of shiitake mushrooms (Lentinula edodes), the farmer needs to know the time needed to water in order to adjust the water content of the logs. To study the enhanced water uptake in the longitudinal direction by shiitake mycelium in shiitake cultivation logs, six dried test logs (Quercus serrata, diameter of 38 to 48 mm, length of 110 to 118 mm) were used. Three test logs had shiitake mycelium grown on them, and the remaining three test logs had mold generated on them. Liquid water was supplied to the bottom surface of the test log which had its longitudinal direction along the line of gravity. Water content distribution in the logs was measured in chronological order using magnetic resonance imaging (MRI) with 1 Tesla. The calibration curve for converting the signal intensity of the MR image into the water content in the test log was determined by cutting the test log at 5-mm intervals and measuring the water content distribution using the mass method. Spatial distribution of the water content of the test log without shiitake mycelium depending on the cumulative water supply time was obtained, and the distribution shape was always concave corresponding to the exact solution of an unsteady one-dimensional diffusion equation with one diffusion coefficient. In the case of the test log in which shiitake mycelium grew, within a few hours after liquid water supply the water content increased in the whole region where shiitake mycelium grew, and the shape of the water content distribution in the longitudinal direction became convex. Based on observation of water penetration into logs by MRI and an optical microscope, it is believed that the driving force behind increased rise in liquid water in the longitudinal direction in the test log is the capillary force acting in vessels.

Enhanced water uptake in the longitudinal direction by shiitake mycelium in shiitake cultivation logs: increase in effective diffusion coefficient based on mass of liquid water uptake.

In the cultivation of shiitake mushrooms (Lentinula edodes), the farmer needs to know the time needed to water in order to adjust the water content of the logs. In this study, six test logs (Quercus serrata, diameter of 38-48 mm, length of 110-118 mm) were used, of which some were dried, some had shiitake mycelia grown on them, and some had mold generated on them. Liquid water was supplied to the test logs by placing the longitudinal direction of the test logs along the line of gravity and immersing the bottom of the test logs in water. Water uptake mass of the test logs was measured for 20 h. The effective diffusion coefficient, D eff, was calculated from the change in time of the water uptake mass using Fick's diffusion law. The D eff of test logs in which shiitake mycelium grew were 1.5-3.4 × 10-8 m2/s, and the values were 2.4-4.7 times higher than that for the dried log. On the other hand, the D eff of the moldy logs were 6.7-9.7 × 10-10 m2/s, which was 0.058-0.081 times that of dry test logs. Based on observation of water penetration into logs by magnetic resonance imaging (MRI) and an optical microscope, it is believed that the driving force behind liquid water rising in the longitudinal direction in the test log is the capillary force acting on a three-phase interface consisting of the inner wall surface of the vessel, liquid water and air. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s00226-021-01313-6.

MRI visualization of shiitake mycelium growing in woodchip blocks used for shiitake mushroom cultivation.

In order to eliminate woodchip blocks where unwanted fungi have grown and select only blocks where shiitake mycelium are growing well, there is a need to develop a visualization technique for shiitake mycelium growing in woodchip blocks, and MRI is an obvious candidate technique. From the results of measurements of the woodchip bed in a small bottle (26 mm inside diameter) where shiitake mycelium was growing, the T1 relaxation time constant immediately after inoculation was 77.9 ±â€¯5.5 ms, and the value after about 10 to 20 days increased to 135.0 ±â€¯9.8 ms (the increase rate was 73%). The T1 maps of the wood-chip block (130 mm length, 75 mm height and 55 mm thickness) in which shiitake mycelium grew were calculated from T1 weighted images measured by changing TR from 28 to 400 ms. From the T1 maps of time series, it was found that the shiitake mycelium extended from the right-hand side to the left-hand side of the woodchip block in a planar manner. Furthermore, in a woodchip block in which penicillium was generated, since the T1 relaxation time constant of only the shiitake mycelium became longer, it was possible to visualize the shiitake mycelium distinctly from penicillium.