Dianjunus Rex Emerges as the Largest Ascomycete Fungus Known to Science
Scientists exploring forests in China’s Yunnan province have identified Dianjunus rex, a giant fungus producing pale yellow, finger-like reproductive structures up to 20 inches tall and weighing nearly five pounds. Discovered by researchers from the Kunming Institute of Botany, this massive organism represents not just a new species, but an entirely new genus and family—Dianjunaceae—within the order Xylariales.
Fieldwork Discoveries Across Yunnan’s Diverse Ecosystems
The initial specimens were gathered by Jing Song on August 5, 2024, close to Damaidi—a settlement situated in Luquan County under the administration of Kunming city within China’s Yunnan Province. During biodiversity surveys, researchers encountered unusual, whitish reproductive structures known as stromata growing from the woody roots of Chinese cork oak trees, emerging directly from the rhizosphere.
While local farmers in the region had previously observed these fleshy, finger-like clusters clustered around dead trees and some had even tasted them without reporting ill effects, the specimens remained scientifically uncatalogued until a local resident sent photographs to researchers at the Kunming Institute of Botany.
DNA Analysis Reveals a New Fungal Family
To investigate the find, researchers deposited voucher specimens in the institute’s collections, cultivated spores under laboratory conditions to examine physical morphology, and sequenced the organism’s genome, including its ensemble of protein-coding genes. DNA analysis confirmed that the organism was sufficiently distinct from known fungi to warrant a new family within Xylariales.
The fungus possesses very few genes for certain enzymes that break down plant tissue, a trait shared with some fungi that live harmlessly inside plants before feeding on them after death.
Fungus Family Originated During Dinosaur Extinction
Using a molecular clock technique to compare the fungus’s DNA with genomic data from other species, the research team estimated that the Dianjunaceae family originated approximately 65 million years ago. This timeline places the evolutionary split near the time of the mass extinction event that eliminated dinosaurs.
Indunil Senanayake, an associate professor at the Germplasm Bank of Wild Species at the Kunming Institute of Botany and coauthor of the study published on September 28 in Frontiers in Fungal Biology, noted that the environmental disruption following the asteroid impact left behind massive amounts of dead plant material. That sudden abundance of dead organic matter likely created new ecological opportunities for wood-associated decomposing fungi.
Dianjunus Rex Exceeds Previous Height Records
Before this discovery, the tallest known fruiting bodies among Ascomycota—the largest major group of fungi with more than 64,000 recognized species—measured between 8 and 12 inches (20 to 30 cm) in height. Dianjunus rex reaches up to 20 inches (50 cm) tall, though the Kenyan bamboo fungus Engleromyces goetzei retains the weight record for the order at approximately 7 pounds (3.2 kg) compared to the 4.9-pound (2.2 kg) maximum of Dianjunus rex.
The evolutionary driver behind such extreme vertical growth remains an active question. Researchers hypothesize that towering above dense forest floor debris and surrounding vegetation allows the fungal structures to catch passing air currents more effectively for wind-driven spore dispersal. However, constructing such a massive organism requires a substantial energy investment, implying that the strategy evolved only where ecological benefits outweighed metabolic costs.
Unexplored Subtropical Biodiversity in East Asian Forests
The discovery shows how much fungal biodiversity remains undocumented in East Asian forests. Subtropical China combines exceptional habitat heterogeneity, climatic stability, and complex biotic interactions that promote fungal diversification. Yet past efforts have frequently fallen short in properly accounting for the true scope of myco-flora here, hampered by field collection challenges, the elusive and seasonally transient nature of mushroom growth, and an overwhelming traditional focus directed solely toward commercially valuable species.
