Changes in the Endophytic Fungal Community Associated with Pilosocereus royenii (Cactaceae) Infested by the Invasive Hypogeococcus sp. (Hemiptera: Pseudococcidae)

Abstract

Entire communities of columnar cacti such as Pilosocereus royenii are being devastated by the infestation of the invasive mealybug Hypogeococcus sp. in Puerto Rico. This insect was first described as Hypogeococcus pungens, but later studies suggest it might be a different, undescribed specie of Hypogeococcus. The use of common insecticides results in a limited control strategy because this insect inhabits deformed plant tissue and covers itself with a protective wax. Generally, endophytic fungi provide the host plant with defenses against biotic and abiotic factors through the production of bioactive compounds that increase plant defenses and their ability to attack pathogens. We studied the community of cultivatable endophytic fungi associated with P. royenii to establish its possible role in the survival of cacti infested with Hypogeococcus sp. We assessed fragments of surface-sterilized plant tissue from asymptomatic and cacti infested by Hypogeococcus sp. The rate of fungal infection and relative frequency of fungal morphotypes isolated from plant tissue was calculated as well as the similarity of the fungal community among individuals. Asymptomatic and infested P. royenii individuals presented similar fungal infection rates. Fungal colonies were isolated from asymptomatic P. royenii tissue and from affected individuals, representing a total of 34 fungal morphotypes. Infested individuals harbored an endophytic fungal community with greater similarity to each other compared to the asymptomatic individuals.