Evidence of fungal decay in petrified legume wood from the Neogene of the Bengal Basin, India

Silicified fossil legume woods of Cynometroxylon Chowdhury & Ghosh collected from the Neogene (late Miocene) sediments of the Bengal Basin, eastern India, exhibit fungal decay seldom found in the fossil record. The wood possesses numerous perforate areas on the surface that seem to be the result of extensive fungal activity. In transverse section, the decayed areas (pockets) appear irregular to ellipsoidal in outline; in longitudinal section these areas of disrupted tissue are somewhat spindle-shaped. Individual pockets are randomly scattered throughout the secondary xylem or are restricted to a narrow zone. The aforesaid patterns of decay in fossil wood show similarities with that of white rot decay commonly produced by higher fungi, specifically basidiomycetes and ascomycetes. The host fossil wood harbors abundant ramifying and septate fungal hyphae with knob like swellings similar to pseudoclamps in basidiomycetes, and three-celled conidia-like reproductive structures. This record expands our current knowledge of wood decaying fungi-host plant interaction in the Neogene tropical forests of Peninsular India. [Abstract copyright: Copyright © 2020 British Mycological Society. Published by Elsevier Ltd. All rights reserved.

Evidence of simultaneous occurrence of tylosis formation and fungal interaction in a late Cenozoic angiosperm from the eastern Himalaya

Information on whether tyloses in fossil angiospermic plants form specifically in response to infestation with pathogenic fungi has been lacking so far, and thus the evolutionary history of tylosis formation as a physical restraint strategy against the advancing fungi remains unresolved. Our study addresses this knowledge lacuna. Carbonized woods were recovered from the upper part of the Siwalik succession (Kimin Formation: late Pliocene to early Pleistocene) of Arunachal Pradesh, eastern Himalaya. Samples from different portions of the wood remains were prepared by using standard thin sectioning techniques and studied under transmitted light compound and scanning electron microscopes. The Plio-Pleistocene wood remains are attributed to Gmelina arborea Roxb. (Lamiaceae) as Gmelina siwalika Khan, Bera M et Bera S, sp. nov. Numerous well-preserved tyloses were found mainly in the central heartwood region of the fossil wood. Rare fungal remains indicative of early-stage colonization are characterized by septate fungal hyphae extending through the vascular ray system within the secondary xylem, and fungal spores. As tyloses are present in large numbers and formed before the spread of fungal remains, they served as an effective physical restraint to the spread of the fungi. We conclude that tylosis formation contributed to an antagonistic relationship between pathogenic fungi and Gmelina plant in Neogene paleoecosystems of the eastern Himalaya. This report also demonstrates that the development of this histological protrusion has been a significant process in woody plant