Color variation of rubberwood clones and cypress infected by Gloeophyllum striatum and Phanerochaete chrysosporium

Abstract

The objective of this work was to examine quantitatively the color changes of six clones of Hevea brasiliensis (IAN 717, IAN 873, GT 711, AVROS 1301, RRIM 600, and Tjir 16) and two cypresses ( Cupressus sp. and Cupressus glauca) upon fungal attack. Samples were exposed to the fungi Gloeophyllum striatum and Phanerochaete chrysosporium according to ASTM D 2017. Wood color was measured in the L ∗ a ∗ b system. Changes in the colorimetric parameters were calculated by the difference between attacked and control samples. None of the rubberwood clones showed weight loss below 25% and therefore could not be classified as resistant, but clones AVROS 1301, RRIM 600, and Tjir 16 were borderline. Both cypresses were resistant to P. chrysosporium, but only Cupressus sp. was resistant to G. striatum. The red tint of all samples exposed to both fungi was slightly intensified (Δ a ∗ > 0), except for RRIM 600. The yellowish tint was intensified as well, except for RRIM 600 and Tjir 16 exposed to G. striatum. Samples attacked by G. striatum were darker than controls (Δ L ∗ < 0), while samples infected by P. chrysosporium were lighter (Δ L ∗ > 0). Color variation mean values (Δ E ∗) ranged from 3.98 to 12.33, attaining the levels appreciable to very appreciable color difference. Extraction of the attacked samples with ethanol–toluene plus hot water removed red and yellow chromophore pigments, causing color variations perceptible to the naked eye.