Botanophila-Epichloë Interaction in a Wild Grass, Puccinellia distans, Lacks Dependence on the Fly Vector

In grass-infecting Epichloë (Ascomycetes: Clavicipitaceae) fungi, the transfer of spermatia for fungal fertilization depends on an insect vector: flies of the genus Botanophila (Diptera: Anthomyiidae). The flies use the fungal stroma, a spore-producing fungal structure surrounding the grass inflorescence, for laying eggs and as a food source for both adults and larvae. This fly-fungus interaction is generally regarded as obligatory and mutualistic. Two Botanophila taxa were noted among four populations of the nonagricultural grass Puccinellia distans (L.) Parl. that were infected with the fungus Epichloë typhina (Pers.) Tul. However, during the 7 yr of field observations, Botanophila flies were present every year in only one population of P. distans. The number of eggs per stroma ranged from zero to four and differed with year and site. Overall, eggs (or larvae) were observed on only 132 (19.2%) of the 687 stromata examined during the survey, with one (13.8%), two (4.5%), or more than two (0.9%) per stroma. However, 90.8% of the examined stromata were fertilized and produced perithecia, suggesting that other mechanisms or vectors of spermatia were responsible for fertilizatio

The fungus Clonostachys epichloë alters the influence of the Epichloë endophyte on seed germination and the biomass of Puccinellia distans grass

The fungal grass endophyte Epichloë typhina (Pers.) Tul. & C. Tul. (Ascomycota: Clavicipitaceae) grows intercellulary in aerial plant parts and reproduces asexually by invading host seeds. In this phase, it enhances seed production and germination, which accelerates its vertical spread. This relationship may be distorted by other seed-born fungi, whose spread is not so directly dependent on the success of the grass. Recently, the fungus Clonostachys epichloë Schroers has been observed on Puccinellia distans (Jacq.) Parl seeds originating from grass clumps infested with stromata, sexual structures of Epichloë typhina that are formed in spring on some host culms, preventing flower and seed development (‘choke disease’). C. epichloë shows mycoparasitic activity toward Epichloë stromata by reducing the production of ascospores, which are responsible for horizontal transmission of the fungus. The aim of this study was to investigate the effect of seed-borne C. epichloë on seed germination, as well as the size and weight of P. distans seedlings and to examine whether C. epichloë alters the influence of Epichloë in the early developmental stages of P. distans. The results showed that if C. epichloë acts on seeds together with E. typhina endophytes, the seeds were negatively affected due to the elimination of the positive effect of the latter in terms of both seed germination rate and seedling length. At the same time, C. epichloë increased the proportion of E. typhina-untreated germinated seeds. Additionally, only the joint action of the two fungi, E. typhina and C. epichloë, effectively stimulated seedling dry mass; the presence of E. typhina alone was not sufficient to noticeably affect seedling size. Based on the increasing commonality of C. epichloë on Epichloë stromata, as well as its potential to be used in biocontrol of ‘choke disease’, we should take a closer look at this fungus, not only in terms of its mycoparasitic ability, but also in terms of its cumulative impact on the whole Epichloë-grass system

Botanophila–Epichloe Interaction in a Wild Grass, Puccinellia distans, Lacks Dependence on the Fly Vector

In grass-infecting Epichloe (Ascomycetes: Clavicipitaceae) fungi, the transfer of spermatia for fungal fertilization depends on an insect vector: flies of the genus Botanophila (Diptera: Anthomyiidae). The flies use the fungal stroma, a spore-producing fungal structure surrounding the grass inßorescence, for laying eggs and as a food source for both adults and larvae. This fly-fungus interaction is generally regarded as obligatory and mutualistic. Two Botanophila taxa were noted among four populations of the nonagricultural grass Puccinellia distans (L.) Parl. that were infected with the fungus Epichloe typhina (Pers.) Tul. However, during the 7 yr of field observations, Botanophila flies were present every year in only one population of P. distans. The number of eggs per stroma ranged from zero to four and differed with year and site. Overall, eggs (or larvae) were observed on only 132 (19.2%) of the 687 stromata examined during the survey, with one (13.8%), two (4.5%), or more than two (0.9%) per stroma. However, 90.8% of the examined stromata were fertilized and produced perithecia, suggesting that other mechanisms or vectors of spermatia were responsible for fertilization

The occurrence and preference of Botanophila flies (Diptera: Anthomyiidae) for particular species of Epichloë fungi infecting wild grasses

Specific associations between species frequently occur in ecological interactions. The aim of this study was to determine the preferences of anthomyiid flies of the genus Botanophila for particular species of fungi as sites for laying eggs and as food for both larvae and adults. The associations of their eggs, larvae and flies with the stromata of different species of Epichloë fungi infecting 7 species of grass in Poland were analyzed. Scanning electron microscopy of the surface of their eggs and an analysis of the genetic sequences of their mitochondrial cytochrome oxidase (COII) were used to identify the taxa of the flies studied. Three types of eggs were distinguished based on their shape, colour and the presence of dorsal folds and sculpturing on the shells. Tentatively,these eggs were assigned to the following species: B. laterella, B. phrenione, B. dissecta and B. lobata. COII sequences obtained from larvae that hatched from two of the types of eggs formed three distinct clades associated with the reference sequences for Botanophila phrenione, B. lobata (new to the fauna of Poland) and a putative species, “Taxon 1”. Only one of these flies (B. lobata) was restricted to a single species of Epichloë (E. bromicola on Elymus repens); B. phrenione was recorded mainly from E. typhina infecting three different species of grass. The results of this study confirm that there is not a close species specific association between this fungus and this insect

Fungus (Epichloë sp.) – fly (Botanophila sp.) interaction in populations of wild grasses

Wydział Biologii: Instytut Biologii ŚrodowiskaU infekujących trawy grzybów z rodzaju Epichloë (Ascomycetes: Clavicipitaceae) transfer spermacjów koniecznych do krzyżowego zapłodnienia zależy od muchówek z rodzaju Botanophila (Diptera: Anthomyiidae). Owady wykorzystują podkładkę grzyba jako miejsce do złożenia jaj oraz źródło pokarmu, również dla wykluwających się z jaj larw. Wcześniejsze doniesienia sugerują, że interakcja ma charakter obligatoryjnego mutualizmu. Badaniami objęto dziko rosnące populacje czterech gatunków traw zainfekowane grzybami Epichloë w Polsce. Oprócz różnic międzygatunkowych, wzięto również pod uwagę czynnik czasu oraz miejsca. Określono gatunki muchówek Botanophila związane z grzybami Epichloë w Polsce (co najmniej jeden z nich to gatunek nowy dla fauny naszego kraju) i zweryfikowano istnienie specyficzności gatunkowej pomiędzy grzybami i muchówkami. Ustalono rolę muchówek w przebiegu cyklu płciowego grzyba, preferencje owadów w stosunku do długości podkładki oraz ich wpływ na dalsze losy ich potomstwa. Wyniki wskazują, że interakcję Botanophila–Epichloë rozpatrywać należy jako zmienną w czasie i przestrzeni. Różnorodne czynniki środowiska, obecność alternatywnych mechanizmów doprowadzających do zapłodnienia grzyba oraz zmienność preferencji muchówek w stosunku do podkładek mogą wpływać na jej charakter i sprawiać, że oscyluje ona pomiędzy mutualizmem a pasożytnictwem.In grass-infecting Epichloë (Ascomycetes: Clavicipitaceae) fungi, the transfer of spermatia for fungal fertilization depends on flies of the genus Botanophila (Diptera: Anthomyiidae). The flies use a fungal stroma for laying eggs and as a food source for both adults and larvae. Previous studies on this fly-fungus association indicate that the fly-fungus interaction is an obligatory mutualism. The Botanophila–Epichloë interaction in wild populations of four grass species infected by Epichloë fungi in Poland was investigated. Apart from intraspecies differences, time and space factors were taken into consideration according to the hypothesis formulated by Bronstein (1994). Fly species connected with Epichloë spp. in Poland (at least one of them is new for the Polish fauna) and specificity of flies for fungal host species were determined. The role of flies in fungal fertilization, fly preferences toward the stroma length and its impact on eggs and larval fate was also assessed. The results indicate that the Botanophila–Epichloë interaction should be considered as highly dynamic in time and space. Different environmental factors, alternative fungal fertilization mechanisms and variability in fly preferences toward fungal size may influence character of this interaction and cause its oscillation between mutualism and parasitism

Botanophila—Epichloë Interaction in a Wild Grass, Puccinellia distans, Lacks Dependence on the Fly Vector

ISSN:0013-8746ISSN:1938-290

Incidence, identification and mycoparasitic activity of Clonostachys epichloë, a hyperparasite of the fungal endophyte Epichloё typhina

Fungi of the genus Epichloë (Clavicipitaceae, Ascomycota) cause choke disease in many grass species. The disease manifests itself as fungal stromata that form around developing inflorescences, thereby suppressing their maturation. Economic losses in agricultural production due to choke have long been known in the U.S.A. and France, but attempts to control choke disease have not been successful. The interaction between Epichloë typhina (Pers.) Tul. & C. Tul. and its naturally occurring fungal hyperparasite, Clonostachys epichloë (Speg.) Schroers (sexual morph Bionectria epichloë) was investigated in populations of the grass Puccinellia distans (L.) Parl. Fungal hyperparasites occur widely in nature, and many are successfully used commercially as biological control agents against plant pathogenic fungi. Microscopy of Epichloë stromata infected with C. epichloë revealed a lack of asci with ascospores in perithecia and damage to mycelia at sites colonized by C. epichloë. The ability of C. epichloë to colonize E. typhina was confirmed via two in vitro experiments. The percent inhibition of growth of E. typhina strains by C. epichloë varied from 18.40 to 46.50%, and the mycoparasite colonized up to 100% of Epichloë mycelia in a precolonization experiment. We discuss the possibility of using C. epichloë to control choke disease caused by E. typhina in grass populations

Botanophila flies, vectors of Epichloë fungal spores, are infected by Wolbachia

Epichloë fungi are endophytes within grasses that can form stromata on culms of their hosts. Botanophila flies visit the stromata for egg laying and in the process can vector spermatial spores, thereby cross fertilising the fungus. Following egg hatch, larval flies consume fungal tissue and spores. Thus, Epichloë individuals with traits that limit larval consumption could be at a selective advantage. We assessed Botanophila fly larvae from sites within the United States and Europe for infection by the bacterial sexual parasite Wolbachia through amplification of the Wolbachia surface protein gene (wsp). Nearly 70% of fly larvae in our samples were infected by Wolbachia. This is the first record of infection by Wolbachia within Botanophila and could have far reaching effects on not only the fly host, but also the Epichloë fungi upon which Botanophila feeds as well as the grass host within which the fungi live. For example, infection by Wolbachia could limit consumption of Epichloë spores by Botanophila larvae if the bacteria promoted premature larval death