Determining the geographic origin of invasive populations of the mealybug Planococcus ficus based on molecular genetic analysis

Authors: DAANE, K - University Of California; MIDDLETON, M - University Of California; SFORZA, RFH - European Biological Control Laboratory (EBCL); KAMP-HUGHES, N - University Of California; ALMEIDA, R - University Of California; CORREA, M - Institut National De La Recherche Agronomique (INRA); DOWNIE, D - California Department Of Pesticide Regulation; WALTON, V - Oregon State University

Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/19/2018
Publication Date: 3/22/2018
Citation: Daane, K., Middleton, M., Sforza, R., Kamp-Hughes, N., Almeida, R., Correa, M., Downie, D., Walton, V. 2018. Determining the geographic origin of invasive populations of the mealybug Planococcus ficus based on molecular genetic analysis. PLoS One. 13(3): e0193852. https://doi.org/10.1371/ journal.pone.0193852.
DOI: https://doi.org/10.1371/ journal.pone.0193852

Interpretive Summary: Mealybugs are major pests of a wide range of crops and ornamental plants worldwide. Many invasive mealybugs have been successfully controlled by the introduction of host-specific parasitic insects (parasitoids), which is known as classical biological control. The vine mealybug, Planococcus ficus, first appeared in California in 1990 and has become an important pest of grapes. It has also invaded other grape-growing areas in North, Central and South America, and South Africa. These invasive populations presumably originated from the Mediterranean basin in the Old World. However, it is important to precisely determine the region from which introduced populations came in order to know where to find well-adapted parasitoids to use for biological control. Foreign exploration was conducted to collect samples of mealybugs from various areas in the Old World. Nuclear and mitochondrial DNA sequences of populations from native and invasive regions were compared to determine their similarity. The results showed two major groups: 1) a European group (Europe, Tunisia, Turkey) and 2) a Middle Eastern group (Israel and Egypt). The invasive populations in North America match the Middle Eastern group and the invasive populations in Argentina and South Africa match the European group. The mealybugs in North American are most similar to those from Israel, so this should be the best place to find host-specific parasitoids. Successful biological control of vine mealybug should provide economical, self-sustaining control of this pest reduce the need to use chemical insecticides.

Technical Abstract: The vine mealybug, Planococcus ficus (Hemiptera: Pseudococcidae), is an invasive mealybug pest of vineyards in Argentina, California, Mexico, Peru and South Africa. This mealybug pest had a previously known geographic distribution spanning southern Europe, the Middle East, and parts of northern Africa. In North America, P. ficus was first discovered in the early 1990s and soon thereafter in Mexico. To determine the origin of invasive populations in North America, P. ficus from California and Mexico were compared with material throughout its presumptive native range in the Mediterranean region, as well as material collected from an older invasion in South Africa and recently invaded Argentina. From each sample location, genomic DNA was sequenced for the nuclear internal transcribed spacer one (ITS1) and the mitochondrial cytochrome C oxidase one (CO1). Phylogenetic analyses of CO1, ITS1 and concatenated CO1 and ITS1 data-sets using Bayesian and neighbor-joining analysis support two major divisions: a European grouping (Europe, Tunisia, Turkey) and a Middle Eastern grouping (Israel and Egypt). The invasive populations in Argentina and South Africa align with the European group and the invasive populations in North America align with the Middle Eastern group. One Israel sample aligns closely with the North American clade, suggesting that Israel is the origin of those populations.