The so-called ambrosia of the Arundo leaf miner, Lasioptera donacis, harbors a diverse endophytic fungal assemblage

Authors: BON, MARIE-CLAUDE - European Biological Control Laboratory (EBCL); Goolsby, John; MERCADIER, GUY - Retired Non ARS Employee; GUERMACHE, FATIHA - European Biological Control Laboratory (EBCL); KASHEFI, JAVID - European Biological Control Laboratory (EBCL); CRISTOFARO, MASSIMO - Bbca-Onlus, Italy; VACEK, ANN - Retired Non ARS Employee; KIRK, ALAN - Retired Non ARS Employee

Submitted to: Diversity
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/17/2023
Publication Date: 4/18/2023
Citation: Bon, M., Goolsby, J., Mercadier, G., Guermache, F., Kashefi, J., Cristofaro, M., Vacek, A., Kirk, A. 2023. The so-called ambrosia of the Arundo leaf miner, Lasioptera donacis, harbors a diverse endophytic fungal assemblage. Diversity. 15(4). Article 571. https://doi.org/10.3390/d15040571.
DOI: https://doi.org/10.3390/d15040571

Interpretive Summary: Arundo donax L., commonly named Giant Reed, is a tall, perennial, bamboo-like grass which is considered one of the world 's 100 worst invasive alien species. Introduced into the U.S. from the old word in the 1800s for erosion control and windbreaks, giant reed has since invaded river banks, streams, ditches and irrigation channels in many states across the U.S.; Texas and California in particular. The weed forms dense stands which displace native vegetation and outcompete shrubs and trees for water resources. Classical biological control by natural enemies is likely to be the only long-term option for controlling the giant reed, and as such, a leaf miner fly, Lasioptera donacis, was recently permitted for release in the U.S. and Mexico. The arundo leafminer fly is highly host-specific to the Giant Reed and therefore poses no significant threats to other native or economically valuable plants. Also, there are two other insects already released in the U.S. for Giant Reed control, the arundo wasp and the arundo scale. It is hypothesized that a combination of damage to the Giant Reed by all three insects will improve the natural biological control if this invasive grass. In the Mediterranean region, the arundo leafminer female lays eggs in young emerging leaf tissue. When the eggs hatch, larvae develop entirely within this tissue and stimulate the growth of fungi which presumably provide food for the larvae. In spite of our growing knowledge on the biology of the arundo leafminer and its interaction with these fungi, it has not yet been demonstrated whether the feeding of the larvae depends on one single fungus or several fungi. This question is essential and needs to be settled before the release of this agent. The fungi have been sampled in 24 populations of Giant Reed infested with the arundo leafminer along the Mediterranean-Latin Arch from Spain to Greece. The molds were analyzed for culturable fungi and were characterized by sequencing a specific DNA region. Our findings show that there is a diversity array of fungi present that appear to be endophytes that naturally live inside the reed without causing apparent disease. In addition, most of them were found naturally occurring inside the giant reed in Texas. This finding is essential as it implies that the larvae of this agent will be able to feed on the reed once released in Texas.

Technical Abstract: The larvae of Lasioptera donacis Coutin feed aggregatively on so-called ambrosia lining galleries within the mesophyll of leaf sheaths of Arundo donax. It has been stated that L. donacis could have established a fundamental symbiotic relationship with ambrosia fungi, although the fungal composition of this ambrosia remains unsettled. Using a culture dependent approach and Internal transcribed spacers sequencing, the present work characterizes and compares the fungal communities associated with this ambrosia in Eurasia with the endophytes of A. donax in Texas where L. donacis is absent. The 65 cultivable isolates obtained from L. donacis ambrosia were sorted into 15 MOTUs, among which Fusarium and Sarocladium predominated. No particular MOTU was systematically recovered from the ambrosia regardless of the sites. The 19 isolates obtained in Texas were sorted into 11 MOTUs. Sarocladium and Fusarium were commonly found in Texas and Eurasia. Our finding indicate that the ambrosia is rather composed of a diverse assemblage of non–systemic endophytes, than an exclusive fungal symbiont. From ovipositors and ovarioles of L. donacis emerging from plants in France, we opportunistically isolated the endophyte Apiospora arundinis which lies at the origin of further research pertaining to its role in the feeding and oviposition of L. donacis