Adaptative Population Genomics of Rachiplusia nu (Lepidoptera: Noctuidae) Under a Tropical Agriculture Landscape.

• Grant number: 24/03382-6
• Support Opportunities: Scholarships in Brazil - Doctorate
• Start date: August 01, 2024
• End date: January 31, 2027
• Field of knowledge: Agronomical Sciences - Agronomy - Plant Health
• Principal Investigator: Alberto Soares Corrêa
• Grantee: Davi de Souza Fernandes
• Host Institution: Escola Superior de Agricultura Luiz de Queiroz (ESALQ). Universidade de São Paulo (USP). Piracicaba , SP, Brazil

Abstract

The Rachiplusia nu caterpillar (Guenée 1852) is a polyphagous species native to southern South America capable of promoting a high rate of defoliation in soybean, bean, sunflower, and vegetable crops. In Brazil, the occurrence of R. nu was restricted to the South region until 2020. However, the species became the predominant caterpillar on soybeans 2023 in more central areas of Brazil (Goiás, Mato Grosso, and Bahia), where it was not commonly reported. This expansion of the spatial scale of Rachiplusia nu population outbreaks is a unique study opportunity to understand the ecological, demographic, and genomic parameters of population outbreaks of a key pest in Brazilian agriculture. Thus, with this project, we sought to study the population genetics of R. nu to understand whether the populations are local or are rising from the South, understand the gene flow between them, and look for signs of structuring according to geographic distance (IBD) or landscape characteristics (IBE). At the same time, we want to understand the bioclimatic factors involved in the distribution of the species of R. nu, characterize the advance in the distribution of the caterpillar, and understand the variables that most correlate with its expansion. Finally, we want to look for signals of genome selection that help in understanding the adaptive process of the species, both climatic characteristics and Bt Cry1Ac soybean crops. To do this, we will describe the advance of the caterpillar throughout Brazilian regions, compare its distribution density, and find the bioclimatic variables associated with this advance. Next, we will build a draft of the R. nu genome to study the population, structural genetic aspects, and the effect of selective pressures on the species' genome. We expect to find a recently expanding population undergoing local, climatic, and host adaptation processes, including detoxification genes, Bt resistance genes, and genes linked to high temperatures. Therefore, with this multidisciplinary project, we hope to understand the demographic and adaptive processes of a species characterized as a pest in new regions of Brazil, contributing to pest management but also to the basic knowledge of evolutionary aspects associated with the expansion of a native species to new agricultural areas in Brazilian territory.