Search

Simple Summary: Previous studies have documented regional susceptibility of the silverleaf whitefly (Bemisia tabaci) to common insecticide active ingredients among populations with different bacterial endosymbionts. Here, we tested the efficacy of 11 different insecticides on three populations of silverleaf whitefly found in Brazil with varying bacterial communities. Significant differences among population responses were measured for four of the tested active ingredients, two of which were neonicotinoids. DNA sequencing detected two types of bacteria in the population more susceptible to insecticides, showing a linkage of host, symbiote, and insecticide resistance. The silverleaf whitefly, Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae), is a significant agricultural pest worldwide, impacting a variety of crop yields. Since the introduction of B. tabaci Mediterranean (MED) species in Brazil, limited research has measured the relative efficacy of the primary insecticides used in whitefly management. This study evaluated the susceptibility of three distinct B. tabaci MED populations to 11 insecticide active ingredients and characterized the bacterial endosymbionts within each population. The insecticides tested were acetamiprid, bifenthrin, cyantraniliprole, diafenthiuron, spiromesifen, imidacloprid, pymetrozine, pyriproxyfen, sulfoxaflor, and thiamethoxam. Results showed varying LC50 and LC90 values among tested insecticides and populations. Notably, populations varied in response to imidacloprid and thiamethoxam with some populations having a 6× higher tolerance. Sequencing data of endosymbionts revealed that individuals from the most susceptible B. tabaci population harbored Rickettsia and Arsenophonus, whereas these bacteria were not detected in the resistant populations. These findings highlight the need for frequent insecticide toxicity bioassays of distinct B. tabaci populations and the adoption of integrated pest management strategies to preserve the efficacy of insecticides for B. tabaci control. Additionally, the role of infection by endosymbionts to alter susceptibility should be further explored. [ABSTRACT FROM AUTHOR]

Simple Summary: Cowpea mild mottle virus (CPMMV) transmitted by the invasive whitefly Bemisia tabaci is a concern for soybean production in Brazil. The Middle East–Asia Minor 1 (MEAM1) and Mediterranean (MED) cryptic species efficiently transmit the virus and resist conventional insecticides, presenting significant challenges to control. Our results indicate a statistically significant difference in the acquisition, inoculation, and retention of CPMMV by Bemisia tabaci MEAM1 and B. tabaci MED cryptic species, with MED being significantly more efficient at transmitting CPMMV compared to MEAM1. Bemisia tabaci MED can also transmit the virus with a shorter acquisition period compared to that of MEAM1, being considered a better vector of CPMMV. Additionally, over three soybean seasons (2019/2020, 2020/2021, and 2021/2022), MEAM1 was predominant across most sites visited, but MED co-occurred with MEAM1 in different places, showing the advancement of this pest in open field areas of Brazil. Cowpea mild mottle virus (CPMMV, genus Carlavirus, family Betaflexividae) is an economically important virus infecting soybeans in Brazil, where it was initially identified in 1983. CPMMV is transmitted by the whitefly, Bemisia tabaci, and occasionally by seeds. Over the last three decades, the most invasive B. tabaci Middle East–Asia Minor 1 (MEAM1), and lately the Mediterranean (MED) cryptic species, have replaced the indigenous species in Brazil, with MEAM1 being predominant. In this study, we investigated the transmission properties of CPMMV by MEAM1 and MED, and their distribution in major soybean-growing areas in São Paulo State. Our results from transmission assays with a single insect revealed that MED is a more efficient vector compared to MEAM1, transmitting the virus within a two-minute inoculation access period. B. tabaci MEAM1 is still the predominant whitefly species in São Paulo State, but MED was also identified in different places, mainly in mixed infestations with MEAM1. Some areas transitioned to a predominance of MED over the three years, while others, where MED had previously been detected, showed a reduction in the insects during the same period. Understanding the transmission dynamics of CPMMV and the distribution of its vectors is crucial for implementing effective management strategies to control the virus spread and protect soybean crops. Further research into the mechanisms driving the shifts in whitefly species dominance and CPMMV distribution will be essential for sustaining soybean production in Brazil. [ABSTRACT FROM AUTHOR]

Six patchouli (Pogostemon cablin Benth.) plants showing symptoms of viral infection were found in Brazil. Transmission electron microscopy revealed flexuous particles and characteristic pinwheel‐shaped cytoplasmic inclusions of potyvirus in sap and cells of symptomatic leaves. Potyvirus infection was confirmed through RT‐PCR, using universal primers followed by nucleotide sequencing. The obtained sequences, comprising part of the CP gene and the 3′ non‐translated region, showed 97.71%–97.87% identity with an isolate of bidens mosaic virus (BiMV). The nucleotide sequences of the CP, HC‐Pro and CI genes of BiMV isolates from patchouli plants were obtained through RT‐PCR with specific primers followed by nucleotide sequencing. The obtained sequences showed 95.78%–97.1% identities with BiMV isolates from Brazil. One BiMV isolate from a patchouli infected plant was sap‐transmitted to different plant species. Chenopodium amaranticolor exhibited local lesions, Bidens pilosa developed leaf mosaic, and Nicotiana benthamiana exhibited chlorosis and stunting. The BiMV isolate was transmitted from infected patchouli plant to B. pilosa using Myzus persicae aphids. This is the first confirmation of patchouli infected with BiMV in Brazil. Further studies are necessary to assess the incidence of this potyvirus in commercial patchouli crops, as well as the damage caused to plant development and the quantity and quality of essential oils produced. [ABSTRACT FROM AUTHOR]

Plumeria pudica, known as bridal bouquet, exhibiting characteristic symptoms of orthotospovirus infection were found in different localities in Brazil. Symptoms were restricted to leaves of the middle and lower thirds of a few branches of each plant. Electron microscopy, molecular analyses, and complete genome sequencing identified the orthotospovirus as groundnut ringspot virus (GRSV),member of the species Orthotospovirus arachianuli. The virus was poorly transmitted mechanically to P. pudica. Reverse transcription polymerase chain reaction (RT-PCR) and reverse transcription quantitative polymerase chain reaction (RT-qPCR) analyses performed using total RNA extracted from leaf blades, primary veins, petioles, and regions of petiole insertion on branches indicated the presence of GRSV, predominantly in the symptomatic leaf blades. Symptomatic branches propagate vegetatively, often resulting in plants expressing GRSV symptoms. In contrast, vegetative propagation of the asymptomatic branches of infected plants predominantly generates plants without GRSV symptoms. The resistance of P. pudica plants to GRSV infection, restricted systemic viral movement, and expression of symptoms in infected plants suggest that this orthotospovirus does not threaten this ornamental plant. [ABSTRACT FROM AUTHOR]

The tomato chlorosis virus (ToCV), transmitted by whitefly species of the genera Bemisia and Trialeurodes in a semipersistent manner, causes significant losses in solanaceous crops including tomato (Solanum lycopersicum) and sweet pepper (Capsicum annuum). Worldwide reports of natural and experimental infection of sweet pepper plants with ToCV are contradictory, raising the question of whether the critical factor determining infection is related to the susceptibility of sweet pepper cultivars or the genetics of virus isolates. In this work, ToCV isolates obtained from different hosts and geographical origins were biologically and molecularly analysed, transmitted by B. tabaci MEAM1 and MED, and the reaction of different sweet pepper cultivars was evaluated under different environmental conditions. Brazilian ToCV isolates from tomato, potato (S. tuberosum), S. americanum, and Physalis angulata did not infect plants of five sweet pepper cultivars when transmitted by B. tabaci MEAM1. Temperatures did not affect the sweet pepper susceptibility to tomato‐ToCV isolates from São Paulo, Brazil, and Florida, USA. However, sweet pepper‐ToCV isolates from Spain and São Paulo, Brazil, were transmitted efficiently to sweet pepper plants by B. tabaci MEAM1 and MED. Although the results indicated that ToCV isolates from naturally infected sweet pepper plants seem to be better adapted to plants of C. annuum, phylogenetic analyses based on the complete nucleotide sequences of RNA1 and RNA2 as well as the p22 gene did not reveal significant nucleotide differences among them. Additional studies are needed to identify intrinsic characteristics of ToCV isolates that favour infection of sweet pepper plants. [ABSTRACT FROM AUTHOR]