First Insights Into the Virus and Viroid Communities in Hemp (Cannabis sativa)

Hemp (Cannabis sativa L.) production has increased significantly in recent years; however, the crop has been understudied in the U.S. since its production declined in the late 1950s. Disease identification and management is an increasing challenge for hemp growers across the country. In 2019, beet curly top virus (BCTV) was first reported in hemp in Colorado. Hence, we were motivated to understand the diversity and prevalence of BCTV strains infecting hemp in Colorado. We detected BCTV at high incidence rate (81%) in leaf samples from 12 counties. Two different strains of BCTV, Worland (Wor) and Colorado (CO) were present as a single or mixed infection in hemp leaf samples. Phylogenetic analysis revealed BCTV sequences from hemp formed a distinct group along with BCTV strains CO and Wor. To determine other potential viral and viroid pathogens in hemp, we performed next generation sequencing (NGS). Virome analysis revealed the presence of both virus and viroid sequences that had high nucleotide sequence identity with GenBank accessions for cannabis cryptic virus, cannabis sativa mitovirus, citrus yellow vein associated virus, opuntia-like virus and hop latent viroid. In contrast, tobacco streak virus sequences were highly variable compared to sequences in GenBank suggesting a possible new genotype of this virus. The data presented here has important implications for the epidemiology and management of the various diseases of hemp and will lead to the development of integrated pest management strategies designed to interrupt transmission cycles and facilitate efficient crop production.

Mining the Genome of Bacillus velezensis VB7 (CP047587) for MAMP Genes and Non-Ribosomal Peptide Synthetase Gene Clusters Conferring Antiviral and Antifungal Activity

Chemical pesticides have an immense role in curbing the infection of plant viruses and soil-borne pathogens of high valued crops. However, the usage of chemical pesticides also contributes to the development of resistance among pathogens. Hence, attempts were made in this study to identify a suitable bacterial antagonist for managing viral and fungal pathogens infecting crop plants. Based on our earlier investigations, we identified Bacillus amyloliquefaciens VB7 as a potential antagonist for managing Sclerotinia sclerotiorum infecting carnation, tobacco streak virus infecting cotton and groundnut bud necrosis infecting tomato. Considering the multifaceted action of B. amyloliquefaciens VB7, attempts were made for whole-genome sequencing to assess the antiviral activity against tomato spotted wilt virus infecting chrysanthemum and antifungal action against Fusarium oxysporum f. sp. cubense (Foc). Genome annotation of the isolate B. amyloliquefaciens VB7 was confirmed as B. velezensis VB7 with accession number CP047587. Genome analysis revealed the presence of 9,231,928 reads with an average read length of 149 bp. Assembled genome had 1 contig, with a total length of 3,021,183 bp and an average G+C content of 46.79%. The protein-coding sequences (CDS) in the genome was 3090, transfer RNA (tRNA) genes were 85 with 29 ribosomal RNA (rRNA) genes and 21 repeat regions. The genome of B. velezensis VB7 had 506 hypothetical proteins and 2584 proteins with functional assignments. VB7 genome had the presence of flagellin protein FlaA with 987 nucleotides and translation elongation factor TU (Ef-Tu) with 1191 nucleotides. The identified ORFs were 3911 with 47.22% GC content. Non ribosomal pepide synthetase cluster (NRPS) gene clusters in the genome of VB7, coded for the anti-microbial peptides surfactin, butirosin A/butirosin B, fengycin, difficidin, bacillibactin, bacilysin, and mersacidin the Ripp lanthipeptide. Antiviral action of VB7 was confirmed by suppression of local lesion formation of TSWV in the local lesion host cowpea (Co-7). Moreover, combined application of B. velezensis VB7 with phyto-antiviral principles M. Jalapa and H. cupanioides increased shoot length, shoot diameter, number of flower buds per plant, flower diameter, and fresh weight of chrysanthemum. Further, screening for antifungal action of VB7 expressed antifungal action against Foc in vitro by producing VOC/NVOC compounds, including hexadecanoic acid, linoelaidic acid, octadecanoic acid, clindamycin, formic acid, succinamide, furanone, 4H-pyran, nonanol and oleic acid, contributing to the total suppression of Foc apart from the presence of NRPS gene clusters. Thus, our study confirmed the scope for exploring B. velezensis VB7 on a commercial scale to manage tomato spotted wilt virus, groundnut bud necrosis virus, tobacco streak virus, S. sclerotiorum, and Foc causing panama wilt of banana.

Virus Diseases of Cereal and Oilseed Crops in Australia: Current Position and Future Challenges

This review summarizes research on virus diseases of cereals and oilseeds in Australia since the 1950s. All viruses known to infect the diverse range of cereal and oilseed crops grown in the continent’s temperate, Mediterranean, subtropical and tropical cropping regions are included. Viruses that occur commonly and have potential to cause the greatest seed yield and quality losses are described in detail, focusing on their biology, epidemiology and management. These are: barley yellow dwarf virus, cereal yellow dwarf virus and wheat streak mosaic virus in wheat, barley, oats, triticale and rye; Johnsongrass mosaic virus in sorghum, maize, sweet corn and pearl millet; turnip yellows virus and turnip mosaic virus in canola and Indian mustard; tobacco streak virus in sunflower; and cotton bunchy top virus in cotton. The currently less important viruses covered number nine infecting nine cereal crops and 14 infecting eight oilseed crops (none recorded for rice or linseed). Brief background information on the scope of the Australian cereal and oilseed industries, virus epidemiology and management and yield loss quantification is provided. Major future threats to managing virus diseases effectively include damaging viruses and virus vector species spreading from elsewhere, the increasing spectrum of insecticide resistance in insect and mite vectors, resistance-breaking virus strains, changes in epidemiology, virus and vectors impacts arising from climate instability and extreme weather events, and insufficient industry awareness of virus diseases. The pressing need for more resources to focus on addressing these threats is emphasized and recommendations over future research priorities provided.

Tobacco streak virus (tobacco streak).

TSV is prevalent in south-eastern Brazil, and can limit yields of soyabeans in some years (Costa and Carvalho, 1961). Epidemics of soyabean bud blight, caused by TSV, were monitored in two soyabean cultivars sown on seven different dates in 1987-88 in Arapoti County, Parana. The highest final level of disease incidence was 60% in 1987 and 90% in 1988 (Almeida et al., 1994a). Brazilian bud blight is also a serious disease in the Santa Fe province of Argentina (Laguna et al., 1988). It occurs in the USA (Fagbenle and Ford, 1970; Kaiser et al., 1982; Sherwood and Jackson, 1985) but is of no economic significance on soyabeans because conditions are not conducive to the development of the problem. TSV presents a major problem in sunflower production in the Indian subcontinent as severe necrosis symptoms may lead to major losses (Bhat et al., 2002).

Sensitive and specific qPCR and nested RT-PCR assays for the detection of Tobacco streak virus in soybean

Tobacco streak virus (TSV) is a re-emerging and understudied pathogen of soybean (Glycine max). Management of TSV is challenging due to the multiple modes of transmission, widespread susceptibility of commercial soybean, and lack of reliable diagnostic tests for the virus. Soybean plants with TSV-like, virus-like, or no symptoms were collected from commercial and research fields in seven counties in Wisconsin. Two sensitive assays were developed for the detection of TSV: a fluorescent dye-based quantitative RT-PCR (qPCR) assay and a nested RT-PCR (nRT-PCR). Tobacco streak virus was detected in 47% and 91% of symptomatic samples using the qPCR assay and the nRT-PCR assay, respectively, suggesting that the nRT-PCR assay has higher sensitivity for detecting TSV. The qPCR assay’s limit of detection was determined at 10 fg and the assay was used to estimate the viral load in TSV-symptomatic samples. The titer of TSV in these samples was determined by absolute quantification and ranged from 15 fg to 0.796 ng. The two assays reported here provide diagnostic tools for the rapid and accurate detection of TSV that can aid in monitoring outbreaks, assessing management strategies, or screening soybean cultivars/accessions for resistance to the virus.

Prevalence and Molecular Characterization Coat Protein Gene of Tobacco streak virus Causing Peanut Stem Necrosis Disease in Coastal and Rayalaseema Districts of Andhra Pradesh, South-India

Background: Peanut stem necrosis disease (PSND) caused by Tobacco streak virus (TSV) is a major constraint for groundnut production in Andhra Pradesh (A.P.). However, studies on prevalence and spread of the disease confined to only few districts of A.P. with this background current study focused on incidence and spread of the disease in entire state of A.P. Further an isolate of TSV occurring in A.P. characterized on the basis of genetic features by comparing with other TSV isolates originated from different hosts and locations from world.Methods: Roving survey was conducted during kharif 2017-18 in groundnut growing districts of Andhra Pradesh (A.P.) for peanut stem necrosis disease incidence. Groundnut plants showing PSND symptoms were collected and tested with direct antigen coating enzyme linked immunosorbent assay (DAC-ELISA). Groundnut samples found positive by ELISA once again tested by reverse transcription polymerase chain reaction (RT-PCR). The representative TSV-GN-INDVP groundnut isolate from Prakasham district was maintained on cowpea seedlings by standard sap inoculation method in glasshouse for further molecular characterization. The Phylogenetic tree for coat protein (CP) gene was constructed using aligned sequences with 1000 bootstrap replicates following neighbor-joining phylogeny.Result: Thirty-eight (52.7%) of seventy-two groundnut samples collected from different locations in A.P were given positive reaction to TSV by DAC-ELISA. For the first time, PSND incidence observed in coastal districts (Krishna, Guntur, Sri Pottisriramulu Nellore, Prakasham) of A.P. Maximum PSND incidence recorded from Bathalapalli (22.2%) and the minimum incidence in Mulakalacheruvu (4.1%). The coat protein (CP) gene of TSV-GN-INDVP groundnut isolate was amplified by RT-PCR and it shared maximum per cent nucleotide identity (97.51-98.62%) with TSV isolates from groundnut and other different crops reported in India. All Indian isolates cluster together irrespective of crop and location based on the phylogenetic analysis.

Composite thrips, Microcephalothrips abdominalis, a new alien species for Bulgarian fauna

Microcephalothrips abdominalis (Crawford, 1910) (Thysanoptera: Thripidae) has been reported as a new alien species for Bulgarian fauna. The composite thrips were recorded during complex research on Thysanoptera diversity in the southwestern part of Bulgaria, with a special emphasis on the locality of the Petrich region. The thrips specimens, especially the adult females were collected on the 18^th of May 2004, but the material was slide-mounted and identified in 2019. The species was found on Calendula officinalis Linnaeus only and has since become established outdoors. M. abdominalis could be a potential threat for this region of Bulgaria, especially in glasshouses with an ability to transmit economically important viruses such as Tobacco Streak Virus (TSV).