No abstract

Citrus canker, caused by the bacterial pathogen Xanthomonas citri subp. Citri (Xcc), is a serious disease reported in most citrus-producing areas around the world. Although different levels of field resistance to citrus canker have been reported in sweet oranges, they are usually not sufficient to provide adequate control of the disease. Ectopic over-expression of antibacterial genes is one of the potential strategies to increase plant resistance to bacterial diseases. Previous in vitro results showed that sarcotoxin IA, an antimicrobial peptide isolated from the flesh fly (Sarcophaga peregrina), can be efficient to control different plant pathogenic bacteria, including Xcc. Transgenic BPera^sweet orange (Citrus sinensis [L.] Osbeck) plants constitutively expressing the sarcotoxin IA peptide fused to the PR1a signal peptide from Nicotiana tabacum for secretion in the intercellular space were obtained by Agrobacteriummediated transformation using thin sections of mature explants. Citrus canker resistance evaluation in leaves of transgenic and non-transgenic plants was performed through inoculations with Xcc by infiltration and spraying. The Xcc population was up to 2 log unit lower in leaves of the transgenic plants compared to those of non-transgenic controls. Incidence of canker lesions was

The control of Salmonella spp. and Campylobacter spp. in chicken meat is essential for avoiding sanitary barriers and preventing human disease. The aim of this study was to develop a multiplex polymerase chain reaction assay (mPCR) for the rapid detection of these bacteria in raw chicken meat. The mPCR was developed using the Styinva‐JHO‐Right and Styinva‐JHO‐Left primers (specific for Salmonella spp.) and the OT1559 and 18‐1 primers (specific for Campylobacter spp.). The specificity of the assay was 100% and it was able to detect 102 cfu/mL of Campylobacter spp. after the selective enrichment and 1 cfu/mL of Salmonella spp. after nonselective enrichment. Fifty raw chicken meat samples were analyzed; 4% were contaminated with Salmonella spp. and 56% with Campylobacter spp. The results obtained using mPCR were confirmed by conventional culturing methods. The developed mPCR method is a relatively inexpensive and efficient means to detect these bacteria after 24 h of enrichment. PRACTICAL APPLICATIONS The developed multiplex polymerase chain reaction method (mPCR) is a relatively inexpensive and efficient means to detect Salmonella spp. and Campylobacter spp. in chicken meat after 24 h of enrichment. The detection of these pathogens in a few hours allows the food supply chain to take appropriate measures quickly to prevent the distribution of contaminated food. Rapid and simultaneous detection of these bacteria in chicken meat can assist in the implementation of the preventive measures that can reduce contamination, which is very useful for Brazil, the third largest producer of chicken meat and the largest exporter of this product. Moreover, the developed mPCR may speed up the identification of suspected colonies of those bacteria on the selective media used in conventional culture methods.

When Huanglongbing (HLB) was found in Brazil in 2004, 'Candidatus Liberibacter americanus' (Lam) was infecting most of the trees while 'Ca. L. asiaticus' (Las) was present in minor proportion. Currently, 'Ca. L. asiaticus' is the predominant bacterium associated with HLB in citrus trees in São Paulo (SP) and Minas Gerais (MG) States, the major citrus growing regions in Brazil. A phytoplasma from 16Sr group IX was associated with HLB symptoms in Brazil in 2007, in plants free of Liberibacter. In this report, HLB-samples testing negative for Las, Lam and 16SrIX phytoplasma, were infected with 16SrIII phytoplasmas. Co-infection with Las and 16SrIII was also found. The 16S rRNA gene sequences from 22 samples were obtained and sequenced, confirming that 16Sr group III phytoplasma is associated with HLB symptoms in SP and MG States. Ten single nucleotide polymorphisms (SNPs) were found in the 1,427 bp 16SrDNA sequences from 16SrIII phytoplasmas from citrus, while none was detected in 16SrDNA sequences among 16SrIX phytoplasma from citrus. Ribosomal protein (rp) rpsSrplVrpsC gene sequences were amplified with 16SrIII group specific primers and sequenced from a subset of nine samples and assembled into three groups based on eight SNPs. SNPs in 16S rRNA and rp gene sequences are common in 16SrIII phytoplasmas from other hosts and this phytoplasma group is widespread in South America. 16SrIII phytoplasmas highly related are commonly found in Melia azedarach, a widespread tree in Brazil and Argentina. The finding of a new phytoplasma associated with HLB symptoms, belonging to the 16SrIII group reinforces the need to develop diagnostic tools to assess HLB associated microbiome.

Huanglongbing (HLB) is a difficult-to-control and highly destructive citrus disease that, in Brazil, is associated mainly with the bacterium ‘Candidatus Liberibacter asiaticus’ transmitted by the psyllid Diaphorina citri. The aim of this study was to improve our understanding of the ‘Ca. L. asiaticus’ infection process by exposing excised, fully expanded, immature citrus leaves in 50-ml Falcon tubes to one, four, or eight adults from a ‘Ca. L. asiaticus’-exposed colony for 1-, 3-, 7-, or 15-day periods for access to inoculation (IAP). The leaves were incubated at 26°C for 1, 3, 7, 15, and 21 days (incubation period [IP]). Infection frequencies and ‘Ca. L. asiaticus’ titers were assessed by quantitative polymerase chain reaction (qPCR). ‘Ca. L. asiaticus’ infection was a function of leaf age, number of insects, IAP, and IP. In general, higher infection rates were observed on younger leaves inoculated with higher numbers of insects and after longer IAP and IP. The immature excised leaf method allowed determination of 3 to 7 days as the range of time required by ‘Ca. L. asiaticus’ to reach qPCR detectable levels. Even though leaf survival could be prolonged by the maintenance of a branch segment at the base of the leaf petiole, leaf degradation, visible after about 15 days IP, did not allow observation of the entire infection process which, in the intact plant, culminates with the appearance of the blotch mottling symptom on leaf blades.

Huanglongbing (HLB) is a destructive disease, associated with psyllid-transmitted phloem-restricted pathogenic bacteria, which is seriously endangering citriculture worldwide. It affects all citrus species and cultivars regardless of the rootstock used, and despite intensive research in the last decades, there is no effective cure to control either the bacterial species (Candidatus Liberibacter spp.) or their insect vectors (Diaphorina citri and Trioza erytreae). Currently, the best attempts to manage HLB are based on three approaches: (i) reducing the psyllid population by intensive insecticide treatments; (ii) reducing inoculum sources by removing infected trees, and (iii) using nursery-certified healthy plants for replanting. The economic losses caused by HLB (decreased fruit quality, reduced yield, and tree destruction) and the huge environmental costs of disease management seriously threaten the sustainability of the citrus industry in affected regions. Here, we have generated genetically modified sweet orange lines to constitutively emit (E)-β-caryophyllene, a sesquiterpene repellent to D. citri, the main HLB psyllid vector. We demonstrate that this alteration in volatile emission affects behavioral responses of the psyllid in olfactometric and no-choice assays, making them repellent/less attractant to the HLB vector, opening a new alternative for possible HLB control in the field.

Citrus species, including sweet oranges, grapefruits, pomelos, and lemons, are the most widely cultivated trees and consumed fruits worldwide. In citrus orchard management, the control of Huanglongbing (HLB) disease and its insect vector Diaphorina citri (Asian citrus psyllid, ACP) represents a major global challenge. Consumers have been increasingly pushing the citrus production chain toward a more sustainable system, including stringent measures to prevent the use of chemical pesticides. In recent years, biotechnological advances have offered safe and environmentally friendly alternatives for crop production. Technologies such as RNA interference (RNAi)-mediated gene silencing have emerged as innovative tools for agricultural pest management. Here, we provide an overview of RNAi as a promising approach for ACP control and discuss the associated challenges. Despite the availability of specific silencing sequences aimed at a target gene of the insect pest, the uptake of double-stranded RNA is limited in hemipteran insects. In this context, improved delivery methods, stability maintenance, and RNAi response are considered the factors contributing to the increased effectiveness of exogenous RNAi against hemipteran pests. These approaches can serve as potential tools for efficient ACP control.

Brazil is one of the three largest beer producers in the world. Four basic ingredients are needed as raw material for the production of beer: water, malt, yeast, and hops (Humulus lupulus L.). Until recently, almost all of the hops in Brazil were imported from other countries. However, in the last decade, hop cultivation in Brazil has emerged due to the increase in the number of new craft breweries, which have demanded diversified raw material for the production of various types of beer. Hops is considered a short-day, temperate species, so the major challenge for the development of hop cultivation in Brazil, with high-yield capacity and with local typicity of bitterness and aroma, is the adaptation of cultivars to the photoperiod conditions in subtropical regions. This review addresses the history of hop cultivation in Brazil and characterizes the main climatic elements of three emerging subtropical growing regions located at different latitudes, such as air temperature, photoperiod, solar radiation, and water availability, to provide support for the development of new technologies for hop cultivation, including supplemental lighting, irrigation, and mulching.