Patterns of genome-wide variation, population differentiation and SNP discovery of the red banded stink bug (Piezodorus guildinii)

Authors: ZUCCHI, MARIA - Universidade De Campinas (UNICAMP); CORDEIRO, ERICK - Universidad De Sao Paulo; Allen, Clint; LAMANA, LETICIA - State University Of Ponta Grossa; VIANA, JOAO P.G. - Universidade De Campinas (UNICAMP); BROWN, PATRICK - University Of Illinois; OMOTO, CELSO - Universidade De Sao Paulo; PINHEIRO, J. BALDIN - Universidad De Sao Paulo; Clough, Steven

Submitted to: Scientific Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/9/2019
Publication Date: 10/9/2019
Citation: Zucchi, M.I., Cordeiro, E., Allen, K.C., Lamana, L.M., Viana, J., Brown, P.J., Omoto, C., Pinheiro, J., Clough, S.J. 2019. Patterns of genome-wide variation, population differentiation and SNP discovery of the red banded stink bug (Piezodorus guildinii). Scientific Reports. 9:14480. https://doi.org/10.1038/s41598-019-50999-z.
DOI: https://doi.org/10.1038/s41598-019-50999-z

Interpretive Summary: The red banded stink bug has recently become an insect pest of soybean in southern United States and has become increasingly important in Brazil. The reasons for its increased pest status in areas of both South and North America are uncertain. There appears to be a range expansion and an increase in densities of red banded stink bug in established locations. To gain insight into the increased appearance of this insect, genetic analysis was performed on field-collected stink bugs from both the U. S. and Brazil. The analysis was used to examine the population structure in these countries and to identify genes under natural selection in both the United States and Brazil. Findings suggests evidence of a hierarchical genetic structure, first separating locations in the U.S. and Brazil, and locations in each country. Genes associated with both plant feeding as well as pesticide tolerance in the red banded sting bug may be under selective pressures contributing to its increase in pest status.

Technical Abstract: Unravelling the details of range expansion and ecological dominance shifts of insect pests has been challenging due to the lack of basic knowledge about population structure, geneflow, and most importantly, how natural selection is affecting the adaptative process. Piezodous guildinii (Westwood) is an emergent insect pest of soybean in the southern region of the United States,and has become increasingly important in Brazil in recent years. However, the reasons P. guildinii is gradually becoming more of a problem and what are the causes for it are questions still largely unanswered. Here we genotyped 7,288 SNPs using genotyping-by-sequencing (GBS) to delineate structure and to identify possible gene candidates under natural selection in both U.S. and Brazilian populations. Our results revealed the existence of a hierarchical genetic structure, first separating locations collected in the U.S. and Brazil (FGT=0.20, p-value=0.000) and locations collected within each country (FST-BR=0.032 and FST-US =0,064, p-value=0.000) according to AMOVA and STRUCTURE (K=2 and K=3) analyses. High levels of geneflow could be inferred from the data, and no spatial pattern was apparent at the finer scale. Lastly, we were able to detect and successfully annotated 92 contigs under direction and balancing selection. The gene ontology (GO) analysis implicated candidate genes under selection with metabolic and cellular processes that can in great extent be associated with herbivory, with two genes having interesting annotations: one candidate gene for selection is a CYP gene that could be related with pesticide tolerance, and the other, an RyR gene, that possibly functions as an odorant-binding protein. We discuss these findings to relate them to recent issues and suggest new efforts that could be implemented to further understand P. guildinii population dynamics.