Nelson Zapata

Genetic variability of the neogregarine Apicystis bombi, an etiological agent of an emergent bumblebee disease.

The worldwide spread of diseases is considered a major threat to biodiversity and a possible driver of the decline of pollinator populations, particularly when novel species or strains of parasites emerge. Previous studies have suggested that populations of introduced European honeybee (Apis mellifera) and bumblebee species (Bombus terrestris and Bombus ruderatus) in Argentina share the neogregarine parasite Apicystis bombi with the native bumblebee (Bombus dahlbomii). In this study we investigated whether A. bombi is acting as an emergent parasite in the non-native populations. Specifically, we asked whether A. bombi, recently identified in Argentina, was introduced by European, non-native bees. Using ITS1 and ITS2 to assess the parasite’s intraspecific genetic variation in bees from Argentina and Europe, we found a largely unstructured parasite population, with only 15% of the genetic variation being explained by geographic location. The most abundant haplotype in Argentina (found in all 9 specimens of non-native species) was identical to the most abundant haplotype in Europe (found in 6 out of 8 specimens). Similarly, there was no evidence of structuring by host species, with this factor explaining only 17% of the genetic variation. Interestingly, parasites in native Bombus ephippiatus from Mexico were genetically distant from the Argentine and European samples, suggesting that sufficient variability does exist in the ITS region to identify continent-level genetic structure in the parasite. Thus, the data suggest that A. bombi from Argentina and Europe share a common, relatively recent origin. Although our data did not provide information on the direction of transfer, the absence of genetic structure across space and host species suggests that A. bombi may be acting as an emergent infectious disease across bee taxa and continents.

Prevalence and phylogenetic analysis of honey bee viruses in the Biobío Region of Chile and their association with other honey bee pathogens

Different episodes of mortalities of honey bee (Apis mellifera L.) colonies have been associated with the presence of honey bee pathogens. Since the Biobio Region has among the highest number of apiaries in Chile, the aim of the present study was to identify viruses in the Region affecting honey bees, evaluate their relation to other pathogens, and conduct a phylogenetic analysis. Pupae and adult bees were collected from 60 apiaries of Apis mellifera L. in the Biobio Region over 2 yr. RNA viruses were detected by reverse transcription PCR (RT-PCR), and Acarapis woodi, Nosema spp., and Varroa destructor via PCR. Three viruses were detected: Acute bee paralysis virus (ABPV), Black queen cell virus (BQCV) and Deformed wing virus (DWV) in 2%, 10%, and 42% of the apiaries, respectively. No statistical correlation was observed between the presence of the different viruses, V. destructor, A. woodi, and the two Nosema species, and the bee development stages. One year after the first sampling, DWV and BQCV were detected mainly in foraging adult bee samples. Three percent of the apiaries were infected with N. apis and 18% with N. ceranae, 5% were positive for V. destructor, while A. woodi was not detected. PCR products were sequenced and compared to the Genbank database. Chilean sequences of ABPV, BQCV, and DWV showed high percentages of similarity to other isolates in South America.

PCR-specific detection of recently described Lotmaria passim (Trypanosomatidae) in Chilean apiaries

The recently described trypanosome Lotmaria passim is currently considered the most predominant trypanosomatid in honey bees worldwide and could be a factor in honey bee declines. For a specific and quick detection of this pathogen, we developed primers based on the SSU rRNA and gGAPDH genes for the detection of L. passim in Chilean honey beehives. PCR products amplified and sequenced for these primers shared 99-100% identity with other sequences of L. passim. The designed primers were specific and we were able to detect a high prevalence (40-90%) of L. passim in bee hives distributed throughout Chile. Our described PCR-based method offers a feasible and specific detection of L. passim in any honey bee samples.

Electrophysiological and behavioral responses of pea weevil Bruchus pisorum L. (Coleóptera: Bruchidae) to volatiles collected from its host Pisum sativum L

The pea weevil (Bruchus pisorum L.) (Coleoptera: Bruchidae) is one of the most damaging pests of pea (Pisum sativum L.) We investigated the role of pea volatiles on the electrophysiological and behavioral response of B. pisorum using electroantennography (EAG) and olfactometry bioassays. Plant volatiles emitted at different phenological stages were collected in situ by headspace on Porapak Q traps and analyzed through gas chromatography coupled to mass spectrometry (GC-MS). Most abundant volatiles identified in all phenological stages were terpenes and green leaf volatiles. All tested volatile extracts elicited significant EAG responses in both male and female B. pisorum, with females exhibiting a greater response (1.35 mV) than males (1.02 mV) to pea-pod volatiles. Volatiles from each phenological stage stimulated an attractant behavioral response of both males and females B. pisorum in olfactometer bioassay. A larger attraction of B. pisorum females was observed to volatiles from pods over other phenological stages (P < 0.001). These results suggest the relative importance of volatiles cues from plant mediating host location by B. pisorum. This work showed that plant volatiles elicited electrophysiological and behavioral responses and that B. pisorum female can discern between phenological stages of P. sativum based on those chemical cues.

The activity of a selected extract of Drimys winteri bark and polygodial on settling and probing behavior of the lettuce aphid Nasonovia ribisnigri

An n-hexane extract and the sesquiterpene polygodial isolated from the bark of Drimys winteri J.R. Forster & G. Forster (Winteraceae) were tested to assess their ability to inhibit settling of the aphid Nasonovia ribisnigri Mosley on lettuce leaves; assessments were made using a choice and no-choice leaf-disk assay. The n-hexane extract and the polygodial both significantly inhibited settling in the choice and no-choice tests, but their application on lettuce leaves did not result in any aphid mortality. Probing behavior of N. ribisnigri on polygodial-treated plants was assessed by means of the electrical penetration graph technique. Polygodial interfered with aphid probing behavior by reducing the total probing time, the number of probes, and the number of intracellular punctures. Aphids did not reach the sieve elements of polygodial-treated plants during the 2-h access period. Both tested compounds have the potential to be used in the development of lettuce aphid control agents to reduce the risk of virus transmission.

Insecticidal activity of a protein extracted from bulbs of Phycella australis Ravenna against the aphids Acyrthosiphon pisum Harris and Myzus persicae Sulzer

Aphids cause significant losses in many agricultural crops and in many cases cause repeated insecticide sprays, which increase the risk of resistance. Therefore, other alternatives are needed to control them. The toxic, anti-reproductive, and feeding deterrent effects of a mannose-binding lectin isolated from bulbs of Phycella australis Ravenna (Amaryllidaceae), named Phycella australis-agglutinin (PAA) was assayed on nymphs of the aphids Acyrthosiphon pisum Harris and Myzus persicae Sulzer fed with an artificial diet. After 72 h of PAA exposure, lethal concentration (LC50) values were 109 and 313 mu g mL(-1) for A. pisum and M. persicae, respectively, while LC90 values were 248 and 634 mu g mL(-1). Sub-lethal concentrations of PAA significantly reduced the aphid fecundity at a concentration of 80 mu g mL(-1). Only a total of 5.7 descendants per female were recorded for A. pisum (32% control progeny) and 12.4 for M. persicae (39% control progeny). Acyrthosiphon pisum was strongly deterred by PAA under choice conditions, as after 72 h exposed to 80 mu g PAA mL(-1) of diet, the feeding deterrent index was 0.91 for A. pisum and only 0.38 for M. persicae. In conclusion, the mannosebinding lectin isolated from bulbs of P. australis showed acute and chronical insecticidal activity against the pea and green peach aphids.

Crecimiento y productividad de dos genotipos de maní (Arachis hypogaea L.) según densidad poblacional establecidos en Ñuble, Chile

espanolEl objetivo de este trabajo fue estudiar el efecto de la densidad poblacional sobre el crecimiento y productividad de mani tipo Espanol y Virginia cultivados en Nuble, Chile. Con cada genotipo se establecio un ensayo de campo en diseno de bloques completos al azar con cuatro repeticiones, considerando cuatro densidades poblacionales entre 104 y 417 mil plantas ha-1. La unidad experimental (12 m2) contenia cuatro hileras espaciadas a 60 cm. La cosecha se realizo 152 dias despues de siembra (DDS). Entre los 73 y 152 DDS se determino area foliar, biomasa acumulada/organo, numero de organos por planta e indice de cosecha. A cosecha se extrajeron las plantas de 3,6 m2 y se determino peso seco de parte aerea, frutos y semillas. Para ambos genotipos el aumento de la densidad poblacional disminuyo significativamente el area foliar, numero de organos y biomasa acumulada por planta. La distribucion de biomasa en la planta no resulto afectada. Por unidad de superficie, mayores densidades implicaron mayor rendimiento de semilla (2.031 y 1.932 kg ha-1 para los genotipos Espanol y Virginia, respectivamente). Altas densidades poblacionales en mani tipo Espanol y Virginia disminuyen el crecimiento por planta, sin embargo, por unidad de superficie, incrementan significativamente la productividad EnglishThe aim of this study was to analyze the effect of population density on growth and productivity of Spanish and Virginia peanuts grown in Nuble, Chile. For each peanut genotype a field trial was established using a randomized complete block design with four replications. Four population densities between 104 and 417 thousand plants ha-1 were used. The experimental unit (12 m2) consisted of four rows spaced at 60 cm. The harvest took place 152 days after sowing (DAS). Between 73 and 152 DAS the leaf area, biomass accumulated per organ, number of organs per plant and harvest index were determined. At harvest, plants contained in 3.6 m2 of each plot were removed, and dry weight of aerial parts, fruits and seeds was determined. For both peanut genotypes, increasing population density decreased leaf area, number of organs and accumulated biomass per plant. The distribution of plant biomass was unaffected. Greater density produced higher seed yield per unit area (2,031 and 1,932 kg ha-1 for Spanish and Virginia genotypes, respectively). High population densities in Spanish and Virginia peanuts reduce individual plant growth, but increase productivity per unit area

Viral and intestinal diseases detected in Apis mellifera in Central and Southern Chile

The honeybee (Apis mellifera L.) is an important pollinator worldwide. Beekeepers have experienced an increasing loss of colonies in recent years and pathologies including viruses and intestinal parasites such as Nosema ceranae are among those held responsible for this decline. The aim of this study was to determine the prevalence and distribution, using the real time PCR method, of six honeybee viruses including Deformed Wing Virus (DWV), Black Queen Cell Virus (BQCV), Sacbrood Virus (SBV), Acute Bee Paralysis Virus (ABPV), Chronic Bee Paralysis Virus (CBPV) and Israeli Acute Paralysis Virus (IAPV) in addition to three intestinal parasites, N. ceranae, N. apis and Lotmaria passim in Chilean beehives distributed between the Metropolitan Region and La Araucania Region. Among the viruses, BQCV was the most prevalent in the analyzed hives, ranging from 72% to 100%, N. ceranae was detected between 19% to 53% and L. passim showed infections ranging from 45% to 73%. Similarly, BQCV (96%) and N. ceranae (42%) were more prevalent in spring-summer whilst DWV (37%) and L. passim (68%) were more frequents in autumn-winter seasons. Furthermore, mixed infections were also detected, wherein viruses were found along with L. passim or viruses with N. ceranae and L. passim, which proved to be the most prevalent. Of the 467 hives analyzed, 97.2% were infected with one or more of the studied pathogens, indicating that they are widely spread in Chile.

Actividad fitotóxica de un extracto N-Hexano obtenido de la corteza de Drimys Winteri sobre cuatro especies de malezas

The objective of this research was to determine the phytotoxic effect of the n-hexane extract obtained from the bark of Drimys winteri on germination and growth of Convolvulus arvensis, Setaria pumila, Daucus carota and Cichorium intybus. The phytotoxic effects of the extract on the germination of weeds were determined by bioassays in Petri dishes, adding the extract on the germination medium at concentrations of 100 to 1,000 mg L-1. The phytotoxic effects of the extract on the emergence and seedling growth of weeds were studied in pots bioassays, where the extract was applied mixed with the growth medium at concentrations of 500 to 4,000 mg kg-1 . We also determined the phytotoxic effects of the extract by spraying on weed plants, at concentrations of 800 to 6,400 mg L-1 . In germination tests, the extract delayed germination and decreased the shoot and radicle growth of all weeds, germination decreased in all weeds except C. arvensis. The application of the extract to the growth medium decreased and delayed the emergence of the weeds, plants treated with the extract had lower height and reduced accumulated biomass. The extract sprayed on plants delayed the growth of the four weed species and decreased their cumulative biomass, plant mortality was observed with the highest concentration tested for S. pumila, D. carota and C. intybus.

Promising antimicrobial activity against the honey bee parasite Nosema ceranae by methanolic extracts from Chilean native plants and propolis

The gut parasite Nosema ceranae is one of the most prevalent honey bee microsporidia worldwide and its chemical management in American countries is mainly based on the antibiotic fumagillin. However, it has recently been reported that this drug has negative side effects in honey bees; therefore, non-harmful alternative treatments must be found. The effects of methanolic extracts (2, 4, 8 and 16%) from Chilean native plant leaves (Aristotelia chilensis, Ugni molinae, and Gevuina avellana) and propolis (Biobío (BB) and Los Ríos (LR) regions) on N. ceranae load, diet consumption and the survival of N. ceranae-infected honey bees were evaluated through oral intake. When bees were N. ceranae-infected and treated with extracts of A. chilensis (8%), U. molinae (2 and 8%) and propolis BB (8%) simultaneously, the N. ceranae load decreased significantly and the survival of infected bees also improved. On the other hand, when bees were first extracts-treated and then N. ceranae-infected, their diet consumption increased and all extracts significantly decreased the N. ceranae load in infected bees. However, only extracts from U. molinae (2 and 8%) and propolis LR (8%) maintained a higher survival rate in infected bees. Natural compounds were also identified; U. molinae and A. chilensis leaves had high concentrations of rutin and myricetin, whereas galangin and pinocembrin were found mostly in southern Chilean propolis (LR). This study constitutes the first report of the antiparasitic activity of propolis against N. ceranae in Apis mellifera and the antimicrobial activity of Chilean plant extracts against this honey bee parasite.