Potential of Acarophenax lacunatus (Prostigmata: Acarophenacidae) as a biological control agent of Rhyzopertha dominica (Coleoptera: Bostrichidae)

A recent report of the parasitic mite species Acarophenax lacunatus (Cross and Krantz) (Prostigmata: Acarophenacidae) attacking populations of Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae) led to the present investigation. Maximum female size and average number of progeny per female mite were assessed at eight different temperatures (ranging from 20 to 41°C) and 60% r.h. using R. dominica as the host. The ability of the mite species to suppress eggs, first instar larvae, and adults of R. dominica was assessed at 30°C and 60% r.h. The largest female sizes of the mite and progeny numbers were obtained around 30°C (259 μm and 17 offspring/female respectively) with minimum values obtained at the most extreme temperatures used in this study. Mite densities of at least four individuals per 500 ml jar containing 50 adults of R. dominica, resulted in almost complete suppression of eggs, first instar larvae, and adults of the host species after 45 days. This same range of mite densities led to reductions of wheat weight losses of 15 and 25% after 45 and 60 days after infestation respectively. Acarophenax lacunatus shows good potential as a biological control agent of R. dominica.

Nicotiana tabacum as an experimental host for the study of plant-Xylella fastidiosa interactions

Xylella fastidiosa causes citrus variegated chlorosis (CVC). Information generated from the X. fastidiosa genome project is being used to study the underlying mechanisms responsible for pathogenicity. However, the lack of an experimental host other than citrus to study plant-X. fastidiosa interaction has been an obstacle to accelerated progress in this area. We present here results of three experiments that demonstrated that tobacco could be an important experimental host for X. fastidiosa. All tobacco plants inoculated with a citrus strain of X. fastidiosa expressed unequivocal symptoms, consisting of orange leaf lesions, approximately 2 months after injection of the pathogen. CVC symptoms were observed in citrus 3 to 6 months after inoculation. The pathogen was readily detected in symptomatic tobacco plants by polymerase chain reaction (PCR) and phase contrast microscopy. In addition, X. fastidiosa was reisolated on agar plates in 4 of 10 plants. Scanning electron microscopy analysis of cross sections of stems and petioles revealed the presence of rod shaped bacteria restricted to the xylem of inoculated plants. The cell size was within the limit typical of X. fastidiosa.

Design of microirrigation systems in sloping lands using linear programming

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Economic viability and selection of irrigation systems using simulation and stochastic dominance

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Effect of temperature on development and population growth of Acarophenax lacunatus (Cross and Krantz) (Prostigmata: Acarophenacidae) on Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae)

The parasitic mite Acarophenax lacunatus kills the eggs upon which it feeds and seems to have potential as a biological control agent of stored grain pests. The lack of biological studies on this mite species led to the present study carried out in laboratory conditions at eight different temperatures (ranging from 20 to 41°C) and 60% relative humidity using Rhyzopertha dominica as host. The higher the temperature, the faster: (1) the attachment of female mites to the host egg (varying from 1 to 5 h); (2) the increase in body size of physogastric females (about twice faster at 40°C than at 20°C); and (3) the generation time (ranging from 40 to 220 h). In addition, the higher the temperature, the shorter the maximum female longevity (ranging from about 75 to 300 h). The two estimated temperature thresholds for development of A. lacunatus on R. dominica were 18 and 40°C. The average number of female and male offspring per gravid mite were 12.8 and 1.0, respectively, with sex ratios (females/total) ranging from 0.91 to 0.94 (maximum at 30°C). The net reproductive rate and intrinsic rate of increase also presented maximum values at 30°C (12.1 and 0.04, respectively).

Transposon Tn1721 distribution among strains of Xylella fastidiosa

Transposons are mobile genetic elements found within the genomes of various organisms including bacteria, fungi, plants and animals. Fragments of the transposon Tn1721 were found included in the genome of Xylella fastidiosa strain 9a5c. Regions from such fragments were PCR-amplified using specially designed primers (TNP1 and TNP2). In order to detect insertions of the Tn1721 element, both primers were used and one of them included a region of the transposon (TNP1) and the other one had the right repeat and part of the bacterial chromosome (TNP2). The PCR products obtained from strain 9a5c were used as a pattern for fragment size comparisons when DNA samples from other X. fastidiosa strains were used as template for the PCR assays. Differences were observed concerning the PCR products of such amplifications when some X. fastidiosa strains isolated from grapevine and plum were used. For the citrus-derived strains only the strains U187d and GP920b produced fragments with different sizes or weak band intensity. Such variations in the X. fastidiosa genome related to disrupted Tn1721 copies are probably due to the possibility of such a transposon element being still able to duplicate even after deletion events might have taken place and also because the bacterial strains in which the main differences were detected are derived from different host plants cultivated under different climate conditions from the one used as reference. © 2002 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.

A review of antifertility folkloric plants tested in laboratory animals

The use of natural active principals is widespread among a great proportion of the rural population, or by people who do not have easy access to medical assistance. These active principles are used as food or medicines, and even for purposes of contraception. It becomes necessary to establish a relationship between the folklore habits and current information on the nature of anti-fertility substances, and knowledge of their mechanisms. Anti-fertility agents may exert their actions in a number of areas, (hypothalamus, anterior pituitary, oviduct, uterus, and vagina), inhibiting synthesis and/or liberation of hormones (follicle-stimulating, luteinizing, and steroid hormones), ovulation, ovum transportation, and implantation process. Therefore, a review of literature was carried out, including of several plants used by women as abortifacient and anti-fertility agents to compare their effects with those obtained among laboratory animals.

Alimentary preconditioning in Acromyrmex subterraneus brunneus workers

Ants suffer a strong environmental influence and are sometimes conditioned for many social activities. To understand better this phenomenon in leaf-cutting ants, 24 colonies of Acromyrmex subterraneus brunneus (Hymenoptera: Formicidae) were conditioned for 2 months with 6 different plants (Citrus spp., Ligustrum spp., Acalypha spp., Eucalyptus spp., Alchornea triplinervia, Melia spp.), to verify alimentary preconditioning in plant selection. After the conditioning period, plants were offered simultaneously, to evaluate the acceptability of each plant species. During foraging, the workers did not exhibit alimentary source fidelity, which was familiarized. This fact suggests the absence of alimentary preconditioning, reinforcing the polyphagic foraging behavior of leaf-cutting ants.

Presence of Xylella fastidiosa in sweet orange fruit and seeds and its transmission to seedlings

Xylella fastidiosa, a xylem-limited bacterium, causes several economically important diseases in North, Central, and South America. These diseases are transmitted by sharpshooter insects, contaminated budwood, and natural root-grafts. X. fastidiosa extensively colonizes the xylem vessels of susceptible plants. Citrus fruit have a well-developed vascular system, which is continuous with the vascular system of the plant. Citrus seeds develop very prominent vascular bundles, which are attached through ovular and seed bundles to the xylem system of the fruit. Sweet orange (Citrus sinensis) fruit of cvs. Pera, Natal, and Valencia with characteristic symptoms of citrus variegated chlorosis disease were collected for analysis. X. fastidiosa was detected by polymerase chain reaction (PCR) in all main fruit vascular bundles, as well as in the seed and in dissected seed parts. No visual abnormalities were observed in seeds infected with the bacterium. However, the embryos of the infected seeds weighed 25% less than those of healthy seeds, and their germination rate was lower than uninfected seeds. There were about 2,500 cells of X. fastidiosa per infected seed of sweet orange, as quantified using real-time PCR techniques. The identification of X. fastidiosa in the infected seeds was confirmed by cloning and sequencing the specific amplification product, obtained by standard PCR with specific primers. X. fastidiosa was also detected in and recovered from seedlings by isolation in vitro. Our results show that X. fastidiosa can infect and colonize fruit tissues including the seed. We also have shown that X. fastidiosa can be transmitted from seeds to seedlings of sweet orange. To our knowledge, this is the first report of the presence of X. fastidiosa in seeds and its transmission to seedlings.

The effect of plant diversity on fungus garden development and foraging behavior of leaf-cutting ants (Hymenoptera: Formicidae)

The leaf-cutting ants forage a wide variety of plant species, used for symbiotic fungus cultivation. To better understand this tripartite complex interaction, 24 colonies of Acromyrmex subterraneus brunneus were conditioned for 4 months to 6 different plants (Citrus spp., Ligustrum spp., Acalypha spp., Eucalyptus spp., Alchornea triplinervia, Melia spp.), to verify the influence of conditioning on foraging behavior of workers. The effect of plants on symbiotic fungus development was studied separately, through macerated plants in Agar and culture medium A as the control. During foraging, workers presented polyphagic foraging behavior, refusing the plants to which they were conditioned. The selection of plants is not correlated with the plant substrate that promotes good development of symbiotic fungus. Such results demonstrate the importance of plant diversity for fungus garden maintenance.

Eficiência de extratos de plantas medicinais e aromáticas em atrair a abelha africanizada (Apis mellifera L.) em cultura de abacateiro (Persea americana Mili.)

The objective of the experiment was to test attractive substances for Africanized honey bees, Apis mellifera L., in avocado, Persea americana Mill. Were pulverized extracts of lemon grass (Cympobogon citratus), ocimum (Ocimum sellowii), Lippia alba, orange leaves (Citrus sinensis), eucaliptus leaves (Eucalyptus sp), eugenol and linalol and the frequency of bees on flowers were evaluated. The frequency of honey bees did increase with the application of the extracts falsa melissa, eucaliptus leaves and orange leaves, used as attractants in Quintal variety. The products tested in Eppendorf tubes did not increased the frequency the bees in Quintal and Fortuna varieties.

Putative pyrophosphate phosphofructose 1-kinase genes identified in sugarcane may be getting energy from pyrophosphate

Pyrophosphate-dependent phosphofructokinase (PPi-PFK) has been detected in several types of plant cells, but the gene has not been reported in sugar cane. Using Citrux paradixi PPi-PFK gene (AF095520 and AF095521) sequences to search the sugar cane EST database, we have identified both the α and β subunits of this enzyme. The deduced amino acid sequences showed 76 and 80% similarity with the corresponding α and β subunits of C. paradisi. A high degree of similarity was also observed among the PFK β subunits when the alignment of the sugar cane sequences was compared to those of Ricinus communis and Solanum tuberosum, it appears that α and β are two distinct subunits; they were found at different concentrations in several sugar cane tissues. It remains to be determined if the different gene expression levels have some physiological importance and how they affect sucrose synthesis, export, and storage in vacuoles. A comparison between the amino acid sequences of β PFKs from a variety of organisms allowed us to identify the two critical Asp residues typical of this enzyme's activity site and the other binding sites; these residues are tightly conserved in all members of this protein family. Apparently, there are catalytic residues on the β subunit of the pyrophosphate-dependent enzyme.

Isolamento de fungos produtores de enzimas pectinolíticas

Soil samples collected in the campus, UNESP, Araraquara, SP, were employed to isolate and characterize fungi strains with potential pectinolytic enzymes. These enzymes have arisen great interest due to its increasing application in the food industry. Two hundred forty six strains were isolated based on the appearance of colony on PDA medium, morphology (septate mycelia, nonseptate conidiophore, black conidia, and clublike spore-bearing head), after 48 h of growth at 30°C. Strains were selected in solid medium containing pectin citrus as sole carbon source and 0.5% rutenium red. The characterization of pectinolytic production was performed in solid culture and batch fermentation medium containing pectin citrus. The enzyme pectinolytic production was evaluated at 30°C, without agitation in 100 mL of medium containing 2% pectin citrus, 0.2% ammonium sulphate, 0.2% magnesium sulphate, and 0.05% potassium phosphate. The maximum pectinolytic activity (15U/mL) was observed in the medium after Aspergillus sp CFCF-0492 growth, while Aspergillus sp CFCF-CC1 showed the higher level of the final biomass. The pectinolytic activity is more preserved when the fungi-spores were maintained in agar-Czapeck medium.

Desempenho e características da carcaça de tourinhos santa gertrudes confinados, recebendo dietas com alto concentrado e níveis crescentes de polpa cítrica peletizada

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Demodicose bovina no estado da Paraíba

Cases of bovine demodicosis caused by Demodex bovis were reported in a Sindhi herd from December 1989 to January 1992. Both localized and generalized forms were diagnosed. This is the first report of the generalized form in Brazil. In the first two years, demodicosis was diagnosed only in cattle < 2 years old, whereas animals of all ages were positive in the last two years. Prevalence varied from 20.4% (11/54) to 53.1% (26/49) and 13.2% (12/91) to 14.8% (9/61) for cattle < 2 years old and > 2 years old, respectively. Clinical signs varied from a few small nodules to a thickened skin with soft large nodules in the localized and generalized forms, respectively. Main microscopic features of the nodules in the generalized form consisted of acanthosis with hyperqueratosis, chronic sebaceous adenitis, subcutaneous muscular necrosis, focal cellular degeneration of the epidermis basal layer and presence of large number of mites inside the lumen of dilated hair follicles. In addition, a chronic perifoliculitis was observed, characterized by lymphoplasmocytic infiltrate which also contained macrophages and neutrophils. It is suggested that poor nutrition and stress due to prolonged drought probably contributed to the increase of susceptibility of the herd to mite infestation.