Soybean Stem Fly, Melanagromyza sojae (Diptera: Agromyzidae), in the New World: detection of high genetic diversity from soybean fields in Brazil.

Soybean Stem Fly (SSF), Melanagromyza sojae (Zehntner), belongs to the family Agromyzidae and is highly polyphagous, attacking many plant species of the family Fabaceae, including soybean and other beans. SSF is regarded as one of the most important pests in soybean fields of Asia (e.g., China, India), North East Africa (e.g., Egypt), parts of Russia, and South East Asia. Despite reports of Agromyzidae flies infesting soybean fields in Rio Grande do Sul State (Brazil) in 1983 and 2009 and periodic interceptions of SSF since the 1940s by the USA quarantine authorities, SSF has not been officially reported to have successfully established in the North and South Americas. In South America, M. sojae was recently confirmed using morphology and its complete mitochondrial DNA (mtDNA) was characterized. In the present study, we surveyed the genetic diversity of M. sojae, collected directly from soybean host plants, using partial mtDNA cytochrome oxidase I (COI) gene, and provide evidence of multiple (>10) maternal lineages in SSF populations in South America, potentially representing multiple incursion events. However, a single incursion involving multiple-female founders could not be ruled out. We identified a haplotype that was common in the fields of two Brazilian states and the individuals collected from Australia in 2013. The implications of SSF incursions in southern Brazil are discussed in relation to the current soybean agricultural practices, highlighting an urgent need for better understanding of SSF population movements in the New World, which is necessary for developing effective management options for this significant soybean pest.

Phylogeography Approach of Diloboderus abderus (Coleoptera: Melolonthidae) in the Southern Cone of America.

Diloboderus abderus (Sturm, 1826) (Coleoptera: Melolonthidae) is a serious soil pest of corn, wheat, oat, and natural and cultivated pastures in Argentina, Paraguay, Uruguay, and southern Brazil. Despite its economic importance, the genetic diversity and population structure of D. abderus remain unknown. We sequenced a fragment of the mitochondrial gene cytochrome oxidase I region (COI), of six populations of D. abderus from the Southern Cone of America. The mtDNA marker revealed a high haplotype diversity, high pairwise FST values, and significant genetic variations among populations. No correlation was found between genetic and geographical distances, yet the most common haplotype (Dab01) was present in four out of the six populations. Analysis of molecular variance showed that most of the variation was within populations of D. abderus. Tajima's D and Fu's FS tests indicated no evidence that D. abderus populations are under recent expansion. Our results indicate that genetic-based traits will likely remain localized or spread slowly, and management strategies need to be undertaken on a small scale.

Hyperexcitability of hippocampal CA1 region in brain slices after GABA withdrawal.

The interruption of GABA infusion in the cerebral cortex and in the hippocampus produces electrographic seizures in rats. Here, we have used the hippocampal slice preparation to induce a 'GABA withdrawal syndrome (GWS)'. With the stimulation parameters used (0.2 Hz, 200 microseconds), activation of the Schaffer afferents produced one population spike in the CA1 subfield, while multiple population spikes were observed in the slices previously incubated in GABA. Also, we recorded an increase in the amplitude of the population spike when compared to its control value. Paired pulse test showed absence of recurrent inhibition in these slices. These results suggest a dysfunction in GABAergic neurotransmission.

Convulsions and wet-dog shakes produced by systemic or intrahippocampal administration of ruthenium red in the rat.

In this work we have studied in the rat the behavioral effects of the intraperitoneal (i.p.) and intrahippocampal (i.h.) administration of ruthenium red (RuR), an inorganic dye which has been shown to inhibit neurotransmitter release in synaptosomes. The i.p. injection induced initially flaccid paralysis and subsequently generalized tonic-clonic convulsions. It contrast, unilateral RuR microinjection into the CA1 area of the hippocampus produced complex seizure behavior and wet-dog shakes (WDS). The i.p. administration of the serotonin receptor antagonist ketanserin markedly inhibited the WDS induced by i.h. RuR. In contrast, the i.h. injection of ketanserin and of the gamma-aminobutyric acid (GABA) agonists 4,5,6,7-tetrahydroisoxazol[5,4-c]pyridin-3-ol(THIP) and baclofen together with RuR did not affect the frequency of WDS nor the seizure behavior. However, the i.h. injection of the GABA uptake blocker nipecotic acid, simultaneously with RuR, increased the frequency of WDS. The release of [3H]GABA, measured in synaptosomes of different cerebral structures of the rats injected i.p. with RuR, and in slices of the CA1 area after i.h. injection of the dye, was not affected. Histological observations of the injected area showed a specific and intense staining of the somas of the CA1 pyramidal neurons. It is concluded that the convulsant action induced by i.h. RuR microinjection is probably the result of an increased excitability of these CA1 neurons, which is independent of any action on GABA release.

Motor alterations and neuronal damage induced by intracerebral administration of Ruthenium red: effect of NMDA receptor antagonists and other anticonvulsant drugs.

The effects of the intracerebroventricular (icv) and the intrahippocampal (ih) microinjection of the inorganic dye Ruthenium red (RuR) on motor activity, and the protective action of excitatory amino acid receptor antagonists and of GABAergic drugs, were studied in the rat. When administered icv, RuR produced intense tonic-clonic convulsions which were refractory to N-methyl-D-aspartate (NMDA) receptor antagonists and to diphenylhydantoin, whereas aminooxyacetic acid (AOA) and valproate only partially protected against seizure activity. The most notable motor effect of the ih RuR administration was the appearance of intense wet-dog shakes (WDS) behavior, which was remarkably attenuated by the icv or intraperitoneal (ip) administration of the NMDA receptor antagonists (+/-)-3-(2-carboxypiperazin-4-yl)-propyl-1-phosphonic acid (CPP), CGP-37849, and MK-801, but not by their ih coinjection with RuR. Systemic AOA and valproate were also effective in reducing the number of WDS, whereas the non-NMDA receptor antagonist CNQX was ineffective. Light and electron microscopic observations of the RuR-injected brains revealed that the dye was highly concentrated in neuronal somas located in or near the injected areas. In the case of the CA1 region, remarkable damage of the pyramidal neurons was manifested by vacuolization, and 5-9 d after the injection notable cell loss and disruption of the CA1 cell layer organization was apparent. The results indicate that RuR penetrates selectively neuronal bodies and damage them, and suggest that the resulting motor alterations involve hyperactivity of glutamatergic neurotransmission.