Delignification pattern of wood decay by white rot fungi in teak (Tectona grandis L. f.)

Abstract

Teak plantations were done in the dry deciduous forests of Gujarat. In this site, the different fungi causing white rot in teak wood were detected. Mostly Lenzites stereoides, Lenzites sp, Ganoderma lucidum, and Hexagonia apiaria isolated from living and dead trees were used to estimate the wood decay through laboratory decay test. The ability of L. stereoides and Corilolus versicolor fungi to degrade teak wood and patterns of decay were analyzed. Decay test revealed that teak wood was very resistance to moderate resistance (i. e. 4.7–27.9) but microscopic observation showed delignification and different pattern of wood decay. Samples incubated with L. stereoides showed delignification in the vessel element, fiber cells and ray cells where as those inoculated with C. versicolor showed mostly degradation of ray cells and fiber cells. In both type of white rot, the delignification processes proceeds in centrifugal direction (i.e. towards lumen of the vessel element). Separation among cells was the main diagnostic feature for selective decay. L. stereoides showed selective decay in fiber cells, ray cells and vessels, where as the C. versicolor showed selective decay in fiber cells and ray cells. Presence of erosion canals, cell wall thinning, bore holes and erosion channels were diagnostic characters of the simultaneous type of decay. Both fungi were able to show selective and simultaneous type of decay in the same wood. Chemical analysis of decayed wood showed highest delignification (i.e. loss of klason lignin) up to 84.71 % by L. stereoides. The decay pattern and delignification processes in teak wood have been reported in India for the first time.