Ribosomal RNA phylogeny of bacterial and fungal pathogens of Agriotes wireworms

Wireworms, the polyphagous larvae of click beetles belonging to the genus Agriotes (Coleoptera: Elateridae), are severe and widespread agricultural pests affecting numerous crops. Biological control agents and methods for this general pest are highly solicited. In a screening for microbial Agriotes pathogens, an intracellular bacterium and a mitosporic fungus were isolated. Phylogenetic analysis based on ribosomal RNA operon sequences of both micro-organisms corroborated their previous morphology-based taxonomic classification. The bacterial pathogen has been assigned to the taxonomic genus Rickettsiella (Gammaproteobacteria) wherein it represents a new pathotype, ‘Rickettsiella agriotidis’, that appears most closely related to subjective synonyms of the nomenclatural type species, Rickettsiella popillae. The fungal pathogen has been shown to belong to the form-species Beauveria bassiana, i.e., an obligate anamorph related to the genus Cordyceps (Ascomycota: Hypocreales). Furthermore, the B. bassiana strain from Agriotes has been shown to be potentially susceptible to identification by gIi-diagnosis, i.e., a diagnostic method making use of the strain-specific presence of self-splicing group-I introns within the ribosomal RNA operons of certain hyphomycetous fungi.     

Hepatozoon spp.: report of some cases in dogs in Brasília, Brazil

Canine hepatozoonosis is a disease caused by the tick-borne protozoan Hepatozoon spp. It has been reported in the United States, southern Europe, the Middle East, Africa and the Far East. In Brazil, canine hepatozoonosis is an emerging protozoal tick-borne disease, and is characterized by distinct clinical signs. The objective of this study was to analyze the laboratory findings of some hepatozoonosis cases in dogs in Brasília, Brazil, and their clinical signs. The animals of this experiment showed low parasitemia, similar to H. americanum, but the clinical signs presented were similar to H. canis. According to our observations and in agreement with O'Dwyer et al. [Vet. Parasitol. 94 (2001) 143], the Brazilian Hepatozoon appears more to resemble the species found in the eastern Hemisphere than with H. americanum of North America, or could be caused by a new species. Our data revealed that hepatozoonosis could be considered endemic in Brasília.     

2n Gamete formation in the genus Brachiaria (Poaceae: Paniceae)

Microsporogenesis of several Brachiaria species of the Brazilian collection at Embrapa Beef Cattle has been analyzed in detail. This paper reports abnormal cytokinesis in three accessions of three different species (Brachiaria humidicola, 2n = 4x = 36, Brachiaria decumbens, 2n = 4x = 36, and Brachiaria dura, 2n = 6x = 54). Chromosomes paired in bi-, tri-, and quadrivalents in these accessions, whereas chromosome segregation at meiosis I was characterized by exclusion of laggards as micronuclei. In a high number of meiocytes, the first sign of cytokinesis appeared only in metaphase II and did not divide the meiocyte into a dyad. Total absence of cytokinesis was also detected among meiocytes in the second division. Since in both cases the two metaphase plates were very close, they favored the rejoining of chromosome sets after anaphase II and formed a restitutional nucleus in telophase II. Second cytokinesis occurred after telophase II in most meiocytes. Monads, dyads, and triads with n or 2n nuclei were observed among meiotic products. The 2n gametes observed correspond to the first division restitution (FDR). The number of affected cells in each accession was variable, but the number of microspores with restitutional nucleus, including those scored in tetrads and the released ones, did not exceed 9%. Although polyploidy is common in the genus Brachiaria, its origin is still unclear. Current results suggest that 2n gametes may have contributed to the evolutionary history of the genus.     

Biomass allocation and foliage heteroblasty in hard pine species respond differentially to reduction in rooting volume

Rooting space is considered as a resource in plants, but comparative studies on the biomass allocation plasticity in response to rooting volume (RV) are rare. We compared responses in growth, biomass allocation and ontogenetic heteroblasty in nine hard pine species of contrasted ecology. Seedlings were cultivated in containers of 0.2, 0.5, 1.0, 2.8 and 7 L for two growing seasons (425 days). Reduction in RV caused a reduction in plant absolute and relative growth rate and biomass allocated to stems but it increased biomass allocated to roots. RV affected to a lesser extent and in a less consistent direction allocation to leaves. Species that grew faster (higher relative growth rate) had a steeper decrease in growth with the reduction in RV. Ontogenetic heteroblasty, evaluated as the proportion of secondary needles in the needle biomass, showed highly different plasticity patterns in response to RV. Decrease in RV caused negligible or no change either in the most ontogenetically delayed Mediterranean pines or in the most ontogenetically advanced pines, the mesic Pinus sylvestris and P. uncinata. By contrast, ontogenetically intermediate species showed steep reaction norms in response to reduction in RV. While P. pinaster and P. brutia showed marked rejuvenation, P. nigra accelerated the development of adult foliage.