ABSTRACT
O objetivo do trabalho foi analisar a estrutura e a diversidade molecular de quatro populações de Spodoptera frugiperda (J.E. Smith) associadas às culturas de milho e arroz no Rio Grande do Sul. Foram coletadas lagartas de quatro populações em áreas isoladas (distanciadas em mais de 300 km) nos municípios de Santa Rosa (milho) e Uruguaiana (arroz irrigado) e em áreas adjacentes, no município de Pelotas (milho e arroz irrigado). A análise de 40 lagartas (10 de cada população), com cinco combinações de oligonucleotídios iniciadores geraram o total de 241 locos, dentre os quais 229 (95 por cento) foram polimórficos. O dendrograma gerado pelo método de agrupamento UPGMA, baseado na matriz de similaridade de Dice, mostrou sobreposições entre as lagartas das populações estudadas. Os índices de diversidade evidenciaram que 88 por cento da diversidade genética foi observada dentro das populações e 12 por cento entre as populações de S. frugiperda. O dendrograma gerado pelo método de agrupamento UPGMA, baseado na matriz de dissimilaridade das distâncias euclidianas, evidenciou a existência de uma diferenciação entre as populações de acordo com a planta hospedeira, sendo os locos 42 e 47 (M-CTG/E-ACC) capazes de detectar 100 por cento das diferenças genéticas. Esses resultados sugerem que a variação genética das populações de S. frugiperda está associada às plantas hospedeiras, confirmando a presença dos biótipos "milho" e "arroz" de S. frugiperda no Rio Grande do Sul.
The goal of this work was to analyze the molecular structure and diversity of four Spodoptera frugiperda (J.E. Smith) populations associated to the corn and rice crops in Rio Grande do Sul State. Four populations of caterpillars were collected from distinct areas (more than 300 km apart), from the counties of Santa Rosa (corn) and Uruguaiana (irrigated rice), and in adjacent areas in Pelotas county (corn and irrigated rice). The analysis of 40 caterpillars (10 from each population), with five combinations of primers generated a total of 241 loci, among then 229 (95 percent) were polymorphic. The dendrogram generated by the clustering method UPGMA, based on the Dice similarity matrix, showed overlappings among the studied populations. The diversity indexes evidenced that 88 percent of the genetic diversity was observed within populations and 12 percent between S. frugiperda populations. The dendrogram generated by clustering UPGMA method, based on the dissimilarity matrix from the euclydean distances, evidenced the existence of a differentiation among populations according to the host plant, being the loci 42 and 47 (M-CTG/E-ACC) capable of detecting 100 percent of the genetic differences. These results showed that the genetic variation of S. frugiperda populations is associated to host plants, confirming the presence of the "corn" and "rice" biotypes of S. frugiperda in Rio Grande do Sul State.
ABSTRACT
The reproductive parameters of Telenomus podisi, Trissolcus brochymenae (Hymenoptera: Scelionidae) and Ooencyrtus sp. (Hymenoptera: Encyrtidae) were studied for three generations on their natural host Podisus nigrispinus (Dallas, 1851) (Hemiptera: Pentatomidae). A parasitism rate of 10 eggs/day/species was used under laboratory conditions of 27 +/- 1 degrees C, 60 +/- 10 percent RH and 14 h of photophase. No significant differences were detected between generations in terms of net reproductive rate (Ro), intrinsic rate of natural increase (rm), generation time (T) and the effect of doubling time on population increase (DT). However, T. podisi and T. brochymenae had significantly higher Ro and rm values, and lower T and DT values, with rm 1.59 and 1.50 times higher than Ooencyrtus sp., respectively. In addition the former species also had shorter egg-adult period, greater longevity of females and reproduction period than the other species. These results confirm the greater reproductive potential of T. podisi and T. brochymenae, which are commonly found parasitizing P. nigrispinus