People: Antonio León Reyes, Noelia Barriga, Dario Ramírez, Corbin Jones, Senay Yitbarek, Beth Shank, Alexi Ann Van Ess, Sarah May Yannarell, Gabrielle Marie Grandchamp, and Diego Riveros-Iregui
There are a total of 238 endemic plant species on the Galapagos Islands, and out of 190 species of the endemic flora, 60% are threatened by the introduction of invasive plant species introduced by anthropogenic activities. Rubus niveus (commonly known as the Mysore, or hill, raspberry) is an invasive plant species that poses one of the greatest threats to the Galapagos ecosystem, covering an estimated 35,000 hectares throughout the archipelago. Its quick ability to grow allows R. niveus to displace native vegetation and threaten native communities of plants.
R. niveus is currently being unsuccessfully managed by manual removal and herbicide application; we are in need of an alternative way to control its spread and ultimately remove it entirely from the Galapagos Islands. Classical biological control (CBC or biocontrol) uses living organisms – natural enemies of invasive species, such as fungal pathogens – to reduce the problem. A successful biological control agent will keep the invasive plant under control and above all, reduce costs of controlling this raspberry significantly. In addition, it will not only reduce the cost of the management of the farmers and the Galapagos National Park, but it would revitalize the native vegetation and its associated fauna.
At the same time, the study of microbes around Rubus (microbiome) is important because they not only play an important role in ecosystems but have also been implicated in plant adaptation. Modern techniques based in DNA, including next generation sequencing, microscopy, chemical imaging, and other techniques are used to explore the mechanisms and molecules through which microbes influence the physiology and behavior of their microbial neighbors. This study of microbial communities within the Galapagos Islands is still relatively limited.
For this reason, our research identifies and evaluates the use of phytopathogens that are endemic to the Galapagos, in order to develop an alternative control of R. niveus and to compare the soil, roots and leaves to understand the adaptation of this plant in different ecosystems. To this end, we collected pathogens that occasionally grow on the fruit or leaves of the endemic raspberry plants on San Cristobal Island and brought them to the Galapagos Science Center to conduct fungi isolation under a potato dextrose agar (PDA) medium. We also collected samples of soil, roots, and leaves to make comparisons between plant genetics and microbial diversity for further studies.
After isolation and purification of samples with lesions, we got 200 isolates of fungi. Using microscopic and molecular analysis, we identified Fusarium concentricum, Penicillium rolfsii, Pestalotia, Colletotricum gloesporoides, Talaromyces sp. and Aspergillus. Further, we tested these isolates of fungi for their pathogenicity, leading to 5 potential candidates which presented lesions over 7 mm of length in Rubus leaves. We will test these 5 candidates as a potential biological control agent of Rubus. In the case of soil samples, roots and leaves to study the microbiome, they have not been yet analyzed.