Resumo O presente estudo analisou os compostos voláteis emitidos pelas plantas de soja Glycine max (cv. FT-Cristalina-RCH): plantas e plantas sadias danificadas mecanicamente ou pelo gorgulho da soja mexicana Rhyssomatus nigerrimus. O método SPME foi utilizado para comparar o perfil volátil de plantas de soja em quatro diferentes condições. O perfil volátil das plantas de G. max infestadas por R. nigerrimus foi qualitativa e quantitativamente diferente do das plantas saudáveis e danificadas mecanicamente. Foi detectada, nos quatro tratamentos, emissão de 59 compostos, dos quais 19 foram identificados por comparação do índice de Kovats, espectro de massa e tempos de retenção com aqueles de padrões sintéticos. Um aumento na concentração dos voláteis acetato de (Z)-3-hexil e do composto 1-octeno-3-ol foi observado quando as plantas de soja foram mecanicamente danificadas. Os compostos produzidos principalmente pela planta de soja durante a infestação por R. nigerrimus macho e fêmea foram 1-octeno-3-ol, 6-metil-5-hepteno-2-ona, (E)-β-ocimeno, salicilaldeído, desconhecido 10, linalol, salicilato de metila, acetato de (Z)-8-dodecenila (éster 5), cetona 2 e geranil acetona. Foram discutidos os efeitos comportamentais dos compostos identificados durante a interação inseto-planta e seus coespecíficos.

Abstract The present study analyzed the volatile compounds emitted by Glycine max (cv. FT-Cristalina-RCH) soybean plants: healthy plants and plants damaged mechanically or by the Mexican soybean weevil Rhyssomatus nigerrimus. The SPME method was used to compare the volatile profile of soybean plants in four different conditions. The volatile profile of G. max plants infested by R. nigerrimus was qualitatively and quantitatively different from that of healthy and mechanically damaged plants. Emission of 59 compounds was detected in the four treatments. Of these compounds, 19 were identified by comparison of the Kovats index, mass spectrum and retention times with those of synthetic standards. An increase in concentration of the volatiles (Z)-3-hexenyl acetate and the compound 1-octen-3-ol was observed when the soybean plants were mechanically damaged. The compounds mostly produced by the soybean plant during infestation by male and female R. nigerrimus were 1-octen-3-ol, 6-methyl-5-hepten-2-one, (E)-β-ocimene, salicylaldehyde, unknown 10, linalool, methyl salicylate, (Z)-8-dodecenyl acetate (ester 5), ketone 2 and geranyl acetone. Behavioral effects of the identified compounds during the insect-plant interaction and their conspecifics are discussed.

A commercial strain of Metarhizium anisopliae (Metchnikoff) Sorokin was used by farmers in 2005 to control the sugarcane froghopper Aeneolamia postica (Walker) in Los Ríos, Tabasco, Mexico. The persistence and the effect of this introduced isolate on the genetic diversity and pathogenicity of the native fungus population are unknown. The purpose of this study was to characterise the genetic diversity and pathogenicity of M. anisopliae isolates collected from sugarcane fields in the region. The Galleria baiting method was used to sample the fungus from the soil, whereas the insect netting method was used to capture adults infected by A. postica. Samples were collected from a total of 33 sugarcane fields. Ten isolates of M. anisopliae were obtained, three in 2007 and seven in 2008; seven isolates were collected near the Usumacinta river. Random amplified polymorphic DNA markers and amplified ribosomal DNA restriction analysis of the 10 isolates revealed the presence of seven subgroups. Two of the isolates obtained in 2008 were genetically similar to the commercial strain used in 2005. At least two genotypes of M. anisopliae were found in this region. No clear relationship between genotype similarity and isolate pathogenicity against A. postica was recorded. Some of the native M. anisopliae isolates are promising candidates as agents of biological control against A. postica.

En 2005, una cepa comercial de Metarhizium anisopliae (Metchnikoff) Sorokin fue aplicada por agricultores contra la mosca pinta Aeneolamia postica (Walker) en Los Ríos, Tabasco, México. Se desconoce la persistencia y el efecto de este aislado introducido sobre la diversidad genética y patogenicidad de las poblaciones nativas del hongo. El objetivo de este estudio fue caracterizar la diversidad genética y patogenicidad de aislados de M. anisopliae colectados en cañaverales de esta región. La técnica del insecto trampa con larvas de Galleria se usó para colectar el hongo del suelo, mientras que una red entomológica se usó para capturar adultos infectados de A. postica. Las muestras se colectaron en un total de 33 cañaverales. En total, se obtuvieron 10 aislados de M. anisopliae, tres en 2007 y siete en 2008; siete de los aislados se colectaron cerca del Río Usumacinta. Marcadores del ADN polimórfico amplificado al azar y análisis de restricción de ADN ribosomal amplificado de los diez aislados, revelaron siete subgrupos. Dos de los aislados obtenidos en 2008 fueron genéticamente similares a la cepa comercial usada en 2005. Al menos dos genotipos de M. anisopliae se encontraron distribuidos en esta región. No hubo una clara relación entre la similitud genética y la patogenicidad de los aislados contra A. postica. Algunos de los aislados nativos de M. anisopliae son candidatos promisorios como agentes de control biológico contra A. postica.