Optimizing the releasing strategy used for the biological control of the sugarcane borer Diatraea saccharalis by Trichogramma galloi with computer modeling and simulation.

One of the challenges in augmentative biological control programs is the definition of releasing strategy for natural enemies, especially when macro-organisms are involved. Important information about the density of insects to be released and frequency of releases usually requires a great number of experiments, which implies time and space that are not always readily available. In order to provide science-based responses for these questions, computational models offer an in silico option to simulate different biocontrol agent releasing scenarios. This allows decision-makers to focus their efforts to more feasible options. The major insect pest in sugarcane crops is the sugarcane borer Diatraea saccharalis, which can be managed using the egg parasitoid Trichogramma galloi. The current strategy consists in releasing 50,000 insects per hectare for each release, in three weekly releases. Here, we present a simulation model to check whether this releasing strategy is optimal against the sugarcane borer. A sensitive analysis revealed that the population of the pest is more affected by the number of releases rather than by the density of parasitoids released. Only the number of releases demonstrated an ability to drive the population curve of the pest towards a negative growth. For example, releasing a total of 600,000 insects per hectare in three releases led to a lower pest control efficacy that releasing only 250,000 insects per hectare in five releases. A higher number of releases covers a wider range of time, increasing the likelihood of releasing parasitoids at the correct time given that the egg stage is short. Based on these results, it is suggested that, if modifications to the releasing strategy are desired, increasing the number of releases from 3 to 5 at weekly intervals is most likely preferable.

Soil insects associated with sugarcane crop in Mato Grosso do Sul, Brazil / Insetos de solo associados à cultura de cana-de-açúcar em Mato Grosso do Sul, Brasil

Pest insects are one of the major factors affecting the productivity of sugarcane, and especially those associated with the soil, which damage the crop if not controlled. There is little information on the insect associated with the soil in the sugarcane crop in the state of Mato Grosso do Sul, Brazil. This study evaluated the occurrence, abundance and population variation of soil-associated insects in sugarcane crops in four counties in the state of Mato Grosso do Sul during a period from September 2009 to August 2010. For the capture of insects, deep in the soil trenches were (50 x 50 x 30 width x length x depth). It was observed that county of Maracaju has a high incidence of soil insects in sugarcane crop. Specimens of the family Scarabaeidae are abundant in sugarcane fields of the state of Mato Grosso do Sul, being Liogenys suturalis the predominant species. Soil insects of the Chrysomelidae family were found with greater abundance in Dourados and Naviraí while Noctuidae, represented only by the Hyponeuma taltula, occurred mainly in Dourados. Insects of the family Termitidae occur in sugarcane fields in the counties of Maracaju and Naviraí but not in Nova Alvorada do Sul and Dourados. Sphenophorus levis and Metamasius hemipterus were alsoreported in the sugarcane fields from Maracaju, being the occurrence these species the first record in the Mato Grosso do Sul State. The determined occurrence of different soil insects in the sugarcane fields may help in their management in the four counties studied.

Os insetos-praga são um dos principais fatores que afetam a produtividade da cana-de-açúcar e, principalmente, aqueles associados ao solo, que prejudicam a cultura se não forem controlados. Existem poucas informações sobre a fauna de insetos associada ao solo na cultura da cana-de-açúcar no estado de Mato Grosso do Sul (MS), Brasil. O objetivo deste estudo foi avaliar a ocorrência, abundância e variação populacional de insetos associados ao solo em lavouras de cana-de-açúcar em quatro municípios do estado de Mato Grosso do Sul durante o período de setembro de 2009 a agosto de 2010. Para a captura de insetos, foram feitas trincheiras (50 cm x 50 cm x 30 cm - largura x comprimento x profundidade) no solo. Observou-se que o município de Maracaju apresenta alta incidência de insetos de solo na cultura da cana-de-açúcar. Exemplares da família Scarabaeidae são abundantes nos canaviais do MS, sendo Liogenys suturalis a espécie predominante. Insetos de solo da família Chrysomelidae foram encontrados com maior abundância em Dourados e Naviraí enquanto Noctuidae, representado apenas por Hyponeuma taltula, ocorreu principalmente em Dourados. Insetos da família Termitidae ocorrem em canaviais nos municípios de Maracaju e Naviraí, mas não em Nova Alvorada do Sul e Dourados. Sphenophorus levis e Metamasius hemipterus (Coleoptera: Curculionidae) também foram encontrados nos canaviais de Maracaju, sendo a ocorrência dessas espécies o primeiro registro no MS. A ocorrência determinada de diferentes insetos de solo nos canaviais auxiliará o manejo nos quatro municípios estudados.

Survey of nematodes associated with sugarcane in the state of Paraná, Brazil

Sugarcane-associated nematodes (Saccharum spp.) can reduce productivity up to 50%. Through the survey, it was possible to identify the main nematodes that occur in a certain region as a tool for designing the best management and control strategies. The aim of this study was to characterize the population of nematodes associated with sugarcane in the North Central, North Pioneiro and Northwest mesoregion of the state of Paraná, Brazil, quantify the nematode genera associated with the crop and identify the species of Pratylenchus and Meloidogyne. A total amount of 89 soil and root composite samples were collected in nine municipalities. Nematodes were extracted and counted in a Peters counting chamber under an optical light microscope. Morphological description followed identification keys. Pratylenchus spp. were identified by morphological characteristics; Meloidogyne spp. were identified by morphological characteristics and isoenzyme electrophoresis. Twelve genera of nematodes associated with sugarcane were identified: Pratylenchus, Meloidogyne, Helicotylenchus, Xiphinema, Mesocriconema, Trichodorus, Aphelenchus, Hoplolaimus, Tylenchus, Tylenchorhynchus, Ditylenchus, and Paratrichodorus. The genera Pratylenchus and Meloidogyne were found with the highest frequencies in the roots. Among the species of Pratylenchus, P. zeae and P. brachyurus were found, with P. zeae being the most frequent. Among the Meloidogyne species, only M. javanica was found. These results are essential to aid decision making in the management of phytonematodes, mainly in the development of new control strategies and in directing genetic breeding programs for development of sugarcane cultivars for the Paraná state.

A new dicistro-like virus from soldier fly, Inopus flavus (Diptera: Stratiomyidae), a pest of sugarcane.

Native Australian soldier flies, Inopus spp. (Diptera: Stratiomyidae), are agricultural pests of economic importance to the sugarcane industry. A screen of the salivary gland transcriptome of Inopus flavus (James) revealed the presence of viral RNA belonging to a potentially novel member of the family Dicistroviridae. The complete genome sequence consists of 9793 nucleotides with two open reading frames. The genome includes two potential internal ribosomal entry sites (IRESs): one within the 5' UTR and the other in the intergenic region (IGR). Virus particles purified from infected larvae and visualised by electron microscopy were found to be icosahedral, non-enveloped, and 30 nm in diameter.

Novel approaches to circumvent the devastating effects of pests on sugarcane.

Sugarcane (Saccharum officinarum L.) is a cash crop grown commercially for its higher amounts of sucrose, stored within the mature internodes of the stem. Numerous studies have been done for the resistance development against biotic and abiotic stresses to save the sucrose yields. Quality and yield of sugarcane production is always threatened by the damages of cane borers and weeds. In current study two problems were better addressed through the genetic modification of sugarcane for provision of resistance against insects and weedicide via the expression of two modified cane borer resistant CEMB-Cry1Ac (1.8 kb), CEMB-Cry2A (1.9 kb) and one glyphosate tolerant CEMB-GTGene (1.4 kb) genes, driven by maize Ubiquitin Promoter and nos terminator. Insect Bio-toxicity assays were carried out for the assessment of Cry proteins through mortality percent of shoot borer Chilo infuscatellus at 2nd instar larvae stage. During V0, V1 and V2 generations young leaves from the transgenic sugarcane plants were collected at plant age of 20, 40, 60, 80 days and fed to the Chilo infuscatellus larvae. Up to 100% mortality of Chilo infuscatellus from 80 days old transgenic plants of V2 generation indicated that these transgenic plants were highly resistant against shoot borer and the gene expression level is sufficient to provide complete resistance against target pests. Glyphosate spray assay was carried out for complete removal of weeds. In V1-generation, 70-76% transgenic sugarcane plants were found tolerant against glyphosate spray (3000 mL/ha) under field conditions. While in V2-generation, the replicates of five selected lines 4L/2, 5L/5, 6L/5, L8/4, and L9/6 were found 100% tolerant against 3000 mL/ha glyphosate spray. It is evident from current study that CEMB-GTGene, CEMB-Cry1Ac and CEMB-Cry2A genes expression in sugarcane variety CPF-246 showed an efficient resistance against cane borers (Chilo infuscatellus) and was also highly tolerant against glyphosate spray. The selected transgenic sugarcane lines showed sustainable resistance against cane borer and glyphosate spray can be further exploited at farmer's field level after fulfilling the biosafety requirements to boost the sugarcane production in the country.

Genetic Engineering Approaches for Enhanced Insect Pest Resistance in Sugarcane.

Sugarcane (Saccharum officinarum), a sugar crop commonly grown for sugar production all over the world, is susceptible to several insect pests attack in addition to bacterial, fungal and viral infections leading to substantial reductions in its yield. The complex genetic makeup and lack of resistant genes in genome of sugarcane have made the conventional breeding a difficult and challenging task for breeders. Using pesticides for control of the attacking insects can harm beneficial insects, human and other animals and the environment as well. As alternative and effective strategy for control of insect pests, genetic engineering has been applied for overexpression of cry proteins, vegetative insecticidal proteins (vip), lectins and proteinase inhibitors (PI). In addition, the latest biotechnological tools such as host-induced gene silencing (HIGS) and CRISPR/Cas9 can be employed for sustainable control of insect pests in sugarcane. In this review overexpression of the cry, vip, lectins and PI genes in transgenic sugarcane and their disease resistance potential is described.

Population dynamics of sugarcane borers, Diatraea spp., under different climatic scenarios in Colombia.

Seasonal temperature and precipitation patterns on a global scale are main factors to which insects and plants adapt through natural selection, although periodic outbreaks in insect populations may occur in areas where they had not been previously reported, a phenomenon considered as a consequence of global warming. In this study, we estimate the distribution of sugarcane borers, Diatraea spp., under different climate scenarios (rcp26, rcp45, rcp60 and rcp85.) Insects were collected weekly in four sugarcane fields from four different towns in the department of Caldas (Colombia) during 2017, and also in several sugarcane fields in the Cauca River Valley (CRV) between 2010 and 2017. The influence of climatic variables on different agro-ecological zones of the CRV sugarcane fields was defined by climatic data between 2010 and 2017 (maximum and minimum daily temperatures, and accumulated precipitation). The estimate of an optimal niche for Diatraea spp. includes temperatures between 20°C and 23°C, accumulated annual rainfall between 1200 and 1500 mm, dry months with precipitations below 50 mm, slopes of less than 0.05 degrees, crop heterogeneity with an index of 0.2 and primary production values of 1.0. Data suggests Diatraea population is considerably influenced by adverse climate change effects, under the premise of an increase in local and global temperatures, reducing its population niches as well as the number of individuals.

An overview of the transcriptional responses of two tolerant and susceptible sugarcane cultivars to borer (Diatraea saccharalis) infestation.

Diatraea saccharalis constitutes a threat to the sugarcane productivity, and obtaining borer tolerant cultivars is an alternative method of control. Although there are studies about the relationship between the interaction of D. saccharalis with sugarcane, little is known about the molecular and genomic basis of defense mechanisms that confer tolerance to sugarcane cultivars. Here, we analyzed the transcriptional profile of two sugarcane cultivars in response to borer attack, RB867515 and SP80-3280, which are considered tolerant and sensitive to the borer attack, respectively. A sugarcane genome and transcriptome were used for read mapping. Differentially expressed transcripts and genes were identified and termed to as DETs and DEGs, according to the sugarcane database adopted. A total of 745 DETs and 416 DEGs were identified (log2|ratio| > 0.81; FDR corrected P value ≤ 0.01) after borer infestation. Following annotation of up- and down-regulated DETs and DEGs by similarity searches, the sugarcane cultivars demonstrated an up-regulation of jasmonic acid (JA), ethylene (ET), and defense protein genes, as well as a down-regulation of pathways involved in photosynthesis and energy metabolism. The expression analysis also highlighted that RB867515 cultivar is possibly more transcriptionally activated after 12 h from infestation than SP80-3280, which could imply in quicker responses by probably triggering more defense-related genes and mediating metabolic pathways to cope with borer attack.

Morphological, chemical and electrophysiological investigations of Telchin licus (Lepidoptera: Castniidae).

The giant sugarcane borer Telchin licus (Drury, 1773) (Lepidoptera: Castniidae) is a day-flying moth pest of sugarcane, pineapples and bananas. To better understand the chemical communication in this species, we examined the morphology of its olfactory system and the chemical composition of its body parts. The ventral surface of the clubbed antennae of T. licus has six morphological types of sensilla: sensilla trichodea, basiconica, chaetica, squamiforma, coeloconica, and auricillica. The telescopic ovipositor shows no evidence of a sexual gland, or female-specific compounds. On the other hand, the midleg basitarsus of males releases (E,Z)-2,13-octadecadienol and (Z,E)-2,13-octadecadienol, which are electroantennographically active in both sexes. These compounds are known female sex pheromones in the Sesiidae family and are male-specific compounds in another castniid moth, although further investigations are necessary to elucidate their ecological role in the Castniidae family.

Field evaluation of sex pheromones and binding specificity of pheromone binding protein 4 in Tryporyza intacta (Lepidoptera: Crambidae).

The recognition of chemical signal including volatile odorants and pheromones is very important in the olfactory physiological behaviors of insects, such as avoiding predators, seeking food and mating partners. The sugarcane borer, Tryporyza intacta is the most harmful insect in sugarcane region in Southeast Asia and Southern China, however, the study of their molecular biology and physiology was limited. Here we demonstrated that the sex pheromone (E11-16:Ald: Z11-16:Ald = 7:3) were most effective to T. intacta. In addition, compared the traditional rubber lure, a new microsphere formulation lure can optimize the trapping effect and might be widely used in the sugarcane growing area. To obtain a better understanding of the olfactory molecular mechanism of pheromone-based mate recognition system, we have cloned the full-length gene of the TintPBP4 and expressed in Escherichia coli. Our phylogenetic analysis highlighted that the TintPBP4 was highly conserved among diverse species of Lepidoptera. Furthermore, the results of QRT-PCR demonstrated that TintPBP4 transcripts were abundantly expressed in the antennae of T. intacta, especially in the male adults. The fluorescence binding experiments showed the TintPBP4 exhibited strong binding capacities to the sex pheromone components. These results will not only provide more understanding for the functional analysis of olfactory proteins from T. intacta, but also assist in the exploitation and development of sex pheromones in the integrated biological control of this pest.

Fragment detection of Coleopteran and Triatomine insects in experimentally contaminated acai pulp and sugarcane juice.

INTRODUCTION: Oral transmission of acute Chagas disease is an emerging public health concern. This study aimed to detect insect fragments in experimentally contaminated food, by comparing triatomines with other insects. METHODS: Food samples were experimentally contaminated with insects, processed to recover their fragments by light filth, and analyzed by microscopy and Polymerase Chain Reaction (PCR). RESULTS: Morphological differences between coleopteran and triatomine insects were observed in microscopic images. PCR was efficient in amplifying Triatominae DNA in the experimentally contaminated food. CONCLUSIONS: This methodology could be utilized by food analysts to identify possible insect contamination in food samples.

Saccharum spontaneum, a Novel Source of Resistance to Root-Lesion and Root-Knot Nematodes in Sugarcane.

Root-lesion nematode (Pratylenchus zeae) and root-knot nematode (Meloidogyne javanica) are two important pathogens of sugarcane (Saccharum hybrid). No commercial cultivars are resistant to these nematodes in Australia. Twenty accession lines of S. spontaneum, a wild relative of sugarcane, were tested against these two nematode species. S. spontaneum lines were tested twice for resistance to root-lesion nematode and three times for root-knot nematode. Reproduction (final population/starting population) of root-lesion nematodes was significantly lower in 17 of the 20 S. spontaneum accession lines tested in two experiments compared with two commercial cultivars. Four S. spontaneum lines supported a significantly lower number of root-lesion nematodes per gram of root than that of two commercial sugarcane cultivars. Reproduction of root-knot nematodes was significantly lower in 16 S. spontaneum lines compared with two commercial cultivars. Fourteen of the S. spontaneum lines tested supported significantly fewer eggs per gram of root compared with two commercial cultivars. This study showed that S. spontaneum lines possessed resistance for root-lesion and root-knot nematodes. Targeted crossing with commercial hybrid parental lines should be conducted to introduce nematode resistance into sugarcane cultivars for the Australian sugar industry.

Early prediction of sugarcane genotypes susceptible and resistant to Diatraea saccharalis using spectroscopies and classification techniques.

The aim of this work was to use spectroscopic methods and partial least squares discriminant analysis (PLS-DA) for the early prediction of genotype resistance or susceptibility to sugarcane borer. The sugarcane leaf +1 was directly analyzed with no sample preparation by ultraviolet-visible-near-infrared (UV-VIS-NIR), middle-infrared (MID), and near-infrared (NIR) spectroscopies. Also, laser-induced breakdown spectroscopy (LIBS) was used to analyze pellets of dried and ground leaves and stalks of sugarcane. Classification models were built using PLS-DA. The models built using UV-VIS-NIR, MID or NIR spectra exhibited ideal sensitivity, specificity, and classification errors, i.e., 1 for both sensitivity and specificity and 0 for classification errors. Regarding the models built using LIBS spectra, those using spectra of pellets made from dried and ground leaves also presented ideal sensitivity, specificity, and classification errors; on the other hand, models built using the spectra of pellets made of dried and ground stalks did not present ideal values for these parameters. Thus, the models built, except for the one using LIBS of pellets made of stalks, showed excellent predictive capacity, making them suitable for predicting the resistance or susceptibility of sugarcane genotypes in the early stages of a plant's life.

Foreign cry1Ac gene integration and endogenous borer stress-related genes synergistically improve insect resistance in sugarcane.

BACKGROUND: Sugarcane (Saccharum spp. hybrids) is considered the most globally important sugar-producing crop and raw material for biofuel. Insect attack is a major issue in sugarcane cultivation, resulting in yield losses and sucrose content reductions. Stem borer (Diatraea saccharalis F.) causes serious yield losses in sugarcane worldwide. However, insect-resistant germplasms for sugarcane are not available in any collections all over the world, and the molecular mechanism of insect resistance has not been elucidated. In this study, cry1Ac transgenic sugarcane lines were obtained and the biological characteristics and transgene dosage effect were investigated and a global exploration of gene expression by transcriptome analysis was performed. RESULTS: The transgene copies of foreign cry1Ac were variable and random. The correlation between the cry1Ac protein and cry1Ac gene copies differed between the transgenic lines from FN15 and ROC22. The medium copy lines from FN15 showed a significant linear relationship, while ROC22 showed no definite dosage effect. The transgenic lines with medium copies of cry1Ac showed an elite phenotype. Transcriptome analysis by RNA sequencing indicated that up/down regulated differentially expressed genes were abundant among the cry1Ac sugarcane lines and the receptor variety. Foreign cry1Ac gene and endogenous borer stress-related genes may have a synergistic effect. Three lines, namely, A1, A5, and A6, were selected for their excellent stem borer resistance and phenotypic traits and are expected to be used directly as cultivars or crossing parents for sugarcane borer resistance breeding. CONCLUSIONS: Cry1Ac gene integration dramatically improved sugarcane insect resistance. The elite transgenic offspring contained medium transgene copies. Foreign cry1Ac gene integration and endogenous borer stress-related genes may have a synergistic effect on sugarcane insect resistance improvement.

Particle Bombardment of the cry2A Gene Cassette Induces Stem Borer Resistance in Sugarcane.

Sugarcane borer is the most common and harmful pest in Chinese sugarcane fields, and can cause damage to the whole plant during the entire growing season. To improve borer resistance in sugarcane, we constructed a plant expression vector pGcry2A0229 with the bar gene as the marker and the cry2A gene as the target, and introduced it into embryogenic calli of most widely cultivated sugarcane cultivar ROC22 by particle bombardment. After screening with phosphinothricin in vitro and Basta spray, 21 resistance-regenerated plants were obtained, and 10 positive transgenic lines harboring the cry2A gene were further confirmed by conventional PCR detection. Real-time quantitative PCR (RT-qPCR) analysis showed that the copy number of the cry2A gene varied among different transgenic lines but did not exceed four copies. Quantitative ELISA analysis showed that there was no linear relationship with copy number but negatively correlated with the percentage of borer-infested plants. The analysis of industrial and agronomic traits showed that the theoretical sugar yields of transgenic lines TR-4 and TR-10 were slightly lower than that of the control in both plant cane and ratoon cane; nevertheless, TR-4 and TR-10 lines exhibited markedly lower in frequency of borer-infested plants in plant cane and in the ratoon cane compared to the control. Our results indicate that the introduction of the cry2A gene via bombardment produces transgenic lines with obviously increased stem borer resistance and comparable sugar yield, providing a practical value in direct commercial cultivation and crossbreeding for ROC22 has been used as the most popular elite genitor in various breeding programs in China.

[Investigation of an outbreak of acute Chagas disease outside the Amazon Region, in Rio Grande do Norte State, Brazil, 2016]. / Investigação de surto de doença de Chagas aguda na região extra-amazônica, Rio Grande do Norte, Brasil, 2016.

The aim of this article was to confirm and describe an outbreak of acute Chagas disease involving oral transmission in the western region of Rio Grande do Norte State, Brazil. This was a descriptive case series study in which the data sources were medical records and interviews with suspected cases from September 16 to November 19, 2015. An entomological investigation was conducted in the probable sites of infection for acute Chagas disease cases. Eighteen cases of acute Chagas disease were confirmed in residents of four municipalities (counties) in Rio Grande do Norte State. The most frequently reported signs and symptoms were fever and weakness (n = 18), followed by myalgia (n = 17), prostration, loss of appetite, and edema of the lower limbs (n = 15). Median duration of fever was 20 days (range: 6 to 45 days). Fifteen cases were confirmed by the laboratory criterion and three by epidemiological link with consistent clinical characteristics. All confirmed cases reported having consumed sugar cane juice from the same mill. A total of 110 triatomines were captured on the plantation where the sugar cane had been crushed for juice. The insects were found in the peridomicile, in stacks of firewood and close to the sugar cane mill. The majority of the captured specimens were Triatoma brasiliensis and showed a natural infection rate of 63%. The Chagas disease outbreak was confirmed with oral transmission via ingestion of sugar cane juice contaminated with infected triatomines, as evidenced by the epidemiological link between the investigated cases and the entomological survey in the probable site where the infection occurred.

O objetivo do artigo foi confirmar e descrever um surto da doença de Chagas aguda por transmissão oral na mesorregião Oeste Potiguar, Rio Grande do Norte, Brasil. Trata-se de um estudo descritivo do tipo série de casos, tendo como fonte de dados os registros de atendimentos médicos e entrevistas com os casos suspeitos entre 16 de setembro e 19 de novembro de 2015. Realizou-se pesquisa entomológica nas prováveis localidades de infecção dos casos de doença de Chagas aguda. Foram confirmados 18 casos de doença de Chagas aguda em residentes de quatro municípios do Rio Grande do Norte. Os sinais e sintomas mais relatados foram febre e fraqueza (n = 18), seguidos de mialgia (n = 17), prostração, inapetência e edema de membros inferiores (n = 15). A mediana de duração da febre foi de 20 dias (intervalo: 6 a 45 dias). Quinze casos foram confirmados por critério laboratorial e três por vínculo epidemiológico com clínica compatível. Todos os casos confirmados relataram ter consumido caldo de cana da mesma procedência. Foram capturados 110 triatomíneos na fazenda onde ocorreu a moagem da cana consumida. Os insetos estavam no peridomicílio, em amontoados de lenha e próximos ao engenho. A maioria dos exemplares capturados era da espécie Triatoma brasiliensis, e apresentou um índice de infecção natural de 63%. Foi confirmado surto da doença de Chagas de transmissão oral por ingestão de caldo de cana contaminado por triatomíneo infectado, evidenciado pelo vínculo epidemiológico entre os casos investigados e a pesquisa entomológica no local provável de infecção.

El objetivo de este artículo fue confirmar y describir un brote de la enfermedad de Chagas aguda por transmisión oral en la mesorregión oeste de Rio Grande do Norte, Brasil. Se trata de un estudio descriptivo del tipo serie de casos, contando como fuente de datos los registros de atención médica y entrevistas en los casos sospechosos entre el 16 de septiembre y el 19 de noviembre de 2015. Se realizó una investigación entomológica en las probables localidades de infección de los casos de enfermedad de Chagas aguda. Fueron confirmados 18 casos de enfermedad de Chagas aguda en residentes de cuatro municipios de Rio Grande do Norte. Los signos y síntomas más informados fueron fiebre y debilidad (n = 18), seguidos de mialgia (n = 17), postración, inapetencia y edema de miembros inferiores (n = 15). La media de duración de la fiebre fue de 20 días (intervalo: 6 a 45 días). Quince casos fueron confirmados por criterio de laboratorio y tres por vínculo epidemiológico con clínica compatible. Todos los casos confirmados informaron haber consumido caldo de caña de la misma procedencia. Fueron capturados 110 triatominos en la hacienda donde se produjo la molienda de la caña consumida. Los insectos estaban en el peridomicilio, en montones de leña y cerca del ingenio azucarero. La mayoría de los ejemplares capturados era de la especie Triatoma brasiliensis, y presentó un índice de infección natural de un 63%. Se confirmó un brote de la enfermedad de Chagas de transmisión oral por ingestión de caldo de caña contaminado por triatomino infectado, evidenciado por el vínculo epidemiológico entre los casos investigados y la investigación entomológica en el lugar probable de infección.

Influence of historical land use and modern agricultural expansion on the spatial and ecological divergence of sugarcane borer, Diatraea saccharalis (Lepidoptera: Crambidae) in Brazil.

Human-mediated changes in landscapes can facilitate niche expansion and accelerate the adaptation of insect species. The interaction between the evolutionary history of the sugarcane borer, Diatraea saccharalis Fabricius, and historical and modern agricultural activity in Brazil shaped its spatial genetic structure, facilitating ecological divergence and incipient host shifting. Based on microsatellite data, STRUCTURE analyses identified two (K = 2) and three (K = 3) significant genetic clusters that corresponded to: (a) a strong signal of spatial genetic structure and, (b) a cryptic signal of host differentiation. We inferred that K = 2 reflects the footprint of agricultural activity, such as expansion of crop production (sugarcane and maize), unintentional dispersion of pests, and management practices. In contrast, K = 3 indicated incipient host differentiation between larvae collected from sugarcane or maize. Our estimates of population size changes indicated that a historical bottleneck was associated with a reduction of sugarcane production ≈200 years ago. However, a more recent population expansion was detected (>1950s), associated with agricultural expansion of large crop production into previously unfarmed land. Partial Mantel tests supported our hypothesis of incipient host adaptation, and identified isolation-by-environment (e.g., host plant) in São Paulo and Minas Gerais states, where sugarcane has been traditionally produced in Brazil. The impact of agricultural production on D. saccharalis may continue, as the current population structure may hinder the efficacy of refuge plants in delaying insect resistance evolution to Bt toxin.

Assessing resistance of sugarcane varieties to sugarcane borer Diatraea saccharalis Fab. (Lepidoptera: Crambidae).

In this study, we investigated resistance traits to the sugarcane borer Diatraea saccharalis Fab. (Lepidoptera: Crambidae) in the leaves and stalks of six sugarcane cultivars in a series of greenhouse and laboratory assays. Investigation of plant factors and infestation rates to better discriminate stalk damage by the sugarcane borer indicated that infestation of 7-month-old, single plants with 20 larvae at the third or fourth instar per plant was suitable to assess tunneling length. Three cultivars (i.e. SP803280, RB928064, and RB835486) had lower stalk damage (i.e. tunnel length) than cultivar SP891115, which exhibited relatively greater susceptibility to tunneling by the borer. The time required for the larvae to enter the sugarcane stalk was longer for cultivar SP803280, indicating resistance traits on the stalk surface, which correlated with lower stalk damage. Larvae feeding on SP813250 stalks had the lowest weight gain, indicating that this cultivar has resistance traits to larval development within its stalks. Cultivars RB867515 and SP891115 resulted in the highest mortality of early-stage larvae feeding on leaves, indicating the presence of resistance factors in their leaves. Multi-trait cluster and principal component analyses placed the cultivars into three and four clusters, respectively. The cultivars placed in different groups that exhibited resistance to leaf feeding, stalk entrance, and tunneling by the sugarcane borer could be used for crossings in sugarcane breeding programs with the goal of obtaining higher levels of resistance to D. saccharalis.

Anatomical, morphological, and physiological responses of two sugarcane genotypes of contrasting susceptibility to Mahanarva fimbriolata (Hemiptera: Cercopidae).

The purpose of this study was to investigate and compare root morpho-anatomical traits and physiological responses of susceptible (SP81-3250) and resistant (H. Kawandang) sugarcane genotypes exposed to the attack by nymphs of spittlebug Mahanarva fimbriolata (Stål) (Hemiptera: Cercopidae). Two experiments were conducted to compare the damage caused by spittlebug nymphs on fresh and dry biomass weight; lignin content in stalks; root anatomy; chlorophyll content; photosynthetic rate (A); carboxylation efficiency (A/Ci); stomatal conductance (gS) and transpiration rate (E) of these genotypes. SP81-3250 consistently obtained significantly higher damage scores than H. Kawandang in both experiments, confirming the previously observed level of resistance in each genotype. Attack by spittlebug nymphs had a much higher effect on both fresh and dry biomass weight, chlorophyll content, A, A/Ci, gs and E of SP81-3250, than that on H. Kawandang. Anatomical studies indicated the presence of aerenchyma tissue in the root cortex of SP81-3250, a feature which may facilitate penetration of the nymph's stylet into the vascular cylinder. In contrast, roots of H. Kawandang are characterized by having more dense and compact parenchyma cells. In addition, infested plants of this genotype contained an unidentified mucilaginous compound in the vascular cylinder of the roots. We conclude that resistance of H. Kawandang to spittlebug is related to the ability of this genotype to maintain normal chlorophyll content, as well as stomatal conductance and photosynthesis, thus, allowing for biomass accumulation under spittlebug attack, in contrast to SP81-3250. In addition, the presence of more compact and denser parenchymal cells, as well as that of an induced mucilaginous compound in the root's vascular cylinder, are likely to hinder host-feeding activity in nymphs, causing higher nymph mortality and therefore, reduced damage in plants of this genotype.

Confirmation that the Novel Cercozoa Phytocercomonas venanatans Is the Cause of the Disease Chlorotic Streak in Sugarcane.

A cercomonad, named Phytocercomonas venanatans, is confirmed as the cause of the sugarcane disease chlorotic streak. This was achieved by establishing aseptic liquid cultures of the pathogen isolated from internal pieces of sugarcane stalk tissue. Actively motile cultures of the pathogen were inoculated into sugarcane roots, stalks, and leaf whorls. Infected plants subsequently developed the characteristic symptoms of chlorotic streak. Infection was confirmed by PCR screening of plant tissues and by reisolation of the pathogen into aseptic culture followed by PCR and microscopic confirmation. P. venanatans is the first reported pathogenic cercomonad able to systemically infect higher plants and the first plant pathogenic cercozoan able to be successfully grown in axenic culture on common microbiological media.