Fungus-insect gall of Phlebopus portentosus

Abstract

Phlebopus portentosus is a popular edible wild mushroom found in the tropical Yunnan, China, and northern Thailand. In its natural habitats, a gall often has been found on some plant roots, around which fungal fruiting bodies are produced. The galls are different from common insect galls in that their cavity walls are not made from plant tissue but rather from the hyphae of P. portentosus. Therefore we have termed this phenomenon “fungus-insect gall”. Thus far six root mealy bug species in the family Pseudococcidae that form fungus-insect galls with P. portentosus have been identified: Formicococcus polysperes, Geococcus satellitum, Planococcus minor, Pseudococcus cryptus, Paraputo banzigeri and Rastrococcus invadens. Fungus-insect galls were found on the roots of more than 21 plant species, including Delonix regia, Citrus maxima, Coffea arabica and Artocarpus heterophyllus. Greenhouse inoculation trials showed that fungus-insect galls were found on the roots of A. heterophyllus 1 mo after inoculation. The galls were subglobose to globose, fulvous when young and became dark brown at maturation. Each gall harbored one or more mealy bugs and had a chimney-like vent for ventilation and access to the gall. The cavity wall had three layers. Various shaped mealy bug wax deposits were found inside the wall. Fungal hyphae invaded the epidermis of plant roots and sometimes even the cortical cells during the late stage of gall development. The identity of the fungus inside the cavity was confirmed by molecular methods.

• black bolete
• China
• fungus-insect gall
• Phlebopus portentosus

Acknowledgments

We thank the staff of American Eagle Editing Office (AEEO) and Alexis Guerin-Laguette for reviewing the paper and providing valuable comments. We thank Wu Y for identifying some specimens of mealy bugs. In particular we thank Xie GS for preparing the figure plates. The study was supported by the National Natural Science Foundation of China (No. 31060271), Research Achievement Transformation Foundation of China (No. 2011GB2F300004), Funds of Sci-Tech Innovation System Construction for Tropical Crops of Yunnan Province (No. RF2014) and Yunnan State Farms Group Program (No. 298). This study also was supported by the New Zealand Institute for Plant & Food Research Ltd.