a1 Embrapa Soja, Caixa Postal 231, Londrina, 86001-970, Paraná State, Brazil
a2 Estación Experimental Agroindustrial Obispo Colombres, Av. William Cross 3150, CPT4101XAC, Las Talitas, Tucuman, Argentina
a3 Instituto Agronômico de Campinas, Centro de Recursos Genéticos, Laboratório de Biologia Molecular. Caixa-Postal, 28 Av. Barão de Itapura, 1481 Centro 13020902, Campinas, SP, São Paulo State, Brazil
a4 Universidade Federal do Paraná, Departamento de Zoologia Caixa Postal 19020, Curitiba, 81531-980, Paraná State, Brazil
Sternechus subsignatus Boheman (Curculionidae: Sternechini) is one of the primary Curculionidae species that reduces soybean yield in Brazil. Initially, outbreaks were reported in southern Brazil in 1973; but, more recent, outbreaks were reported in Bahia (summer 1997–1998) and Maranhão (summer 2003–2004), two states in northeastern Brazil. A putative related species, S. pinguis (Fabricius), was first detected in Salta Province, Argentina. The objective of this study was to evaluate intraspecific molecular polymorphisms of geographically distinct Sternechus populations. Randomly amplified polymorphic DNA (RAPD) profiles and partial mitochondrial cytochrome B (CytB) gene sequences were used to determine whether individual soybean stalk weevils were one of two different species and to infer pest invasion pattern. Putative S. pinguis and S. subsignatus populations were collected in San Agustin (Cruz Alta, Tucumán Province, Argentina) and different sampling sites in the Brazilian states of Paraná, Bahia and Maranhão. Polymorphic bands were obtained by RAPD and analyzed by Dice coefficients. Populations from southern Brazil were more closely related genetically to an Argentinean group than the populations sampled in northeastern Brazil. The Londrina Co., Brazil population displayed the highest intra-population genetic similarity. Most of the soybean stalk weevils collected from San Agustin, Tucumán, Argentina were divergent from those collected in Brazil. Sequencing and parsimony analysis of CytB did not differentiate specimens collected in Argentina and Brazil. Thus, our data show that soybean stalk weevil outbreaks and population increases in northeastern Brazil involved local genotypes.
(Accepted December 05 2007)
(Online publication June 16 2008)