Beet curly top virus (BCTV) ELISA Kit

Geminiviruses are single-stranded DNA plant viruses with circular genomes packaged within geminate particles. Among theGeminiviridaefamily,BegomovirusandCurtoviruscomprise the two best characterized genera. Curtovirus and Old World begomovirus possess similar genome structures with six to seven open-reading frames (ORF). Among them, begomovirus and curtovirus V2 ORFs share the same location in the viral genome, encode proteins of similar size, but show extremely poor sequence homology between the genera. V2 fromBeet curly top virus(BCTV), the model species for theCurtovirusgenus, as it begomoviral counterpart, suppresses post-transcriptional gene silencing (PTGS) by impairing the RDR6/SGS3 pathway and localizes in the nucleus spanning from the perinuclear region to the cell periphery. By aminoacid sequence comparison we have identified that curtoviral and begomoviral V2 proteins shared two hydrophobic domains and a putative phosphorylation motif. These three domains are essential for BCTV V2 silencing suppression activity, for the proper nuclear localization of the protein and for systemic infection. The lack of suppression activity in the mutated versions of V2 is complemented by the impaired function of RDR6 inNicotiana benthamianabut the ability of the viral mutants to produce a systemic infection is not recovered in gene silencing mutant backgrounds. We have also demonstrated that, as its begomoviral homolog, V2 from BCTV is able to induce systemic symptoms and necrosis associated with a hypersensitive response-like (HR-like) when expressed from Potato virus X vector inN. benthamiana, and that this pathogenicity activity does not dependent of its ability to supress PTGS.

Beet curly top virus (BCTV) limits sugarbeet production considerably. Previous studies have shown that infections are associated with the generation of defective DNAs (D-DNA) which may attenuate symptoms. Transgenic sugarbeet lines were established carrying a partial direct repeat construct of D-DNA in order to examine whether they are useful as a means of generating tolerance against BCTV. Thirty four independent transgenic lines were challenged. Viral full-length and D-DNAs were monitored by polymerase chain reaction (PCR) or rolling circle amplification (RCA) and restriction fragment length polymorphism (RFLP). The differential accumulation of both DNA species was compared with symptom severity during the course of infection. RCA/RFIP allowed the discrimination of two D-DNA classes which were either derived from the transgenic construct (D-0) or had been generated de novo (D-n). The statistical analysis of the results showed that the presence of D-0-DNA correlated with increased symptom severity, whereas D-n-DNAs correlated with attenuated symptoms. (C) 2011 Elsevier B.V. All rights reserved.

Curly top of sugar beet is a serious, yield-limiting disease in semiarid production areas caused by Beet curly top virus (BCTV) and transmitted by the beet leafhopper. One of the primary means of control for BCTV in sugar beet is host resistance but effectiveness of resistance can vary among BCTV strains. Strain prevalence among BCTV populations was last investigated in Idaho and Oregon during a 2006-to-2007 collection but changes in disease severity suggested a need for reevaluation. Therefore, 406 leaf samples symptomatic for curly top were collected from sugar beet plants in commercial sugar beet fields in Idaho and Oregon from 2012 to 2015. DNA was isolated and BCTV strain composition was investigated based on polymerase chain reaction assays with strain-specific primers for the Severe (Svr) and California/Logan (CA/Logan) strains and primers that amplified a group of Worland (Wor)-like strains. The BCTV strain distribution averaged 2% Svr, 30% CA/Logan, and 87% Wor-like (16% had mixed infections), which differed from the previously published 2006-to-2007 collection (87% Svr, 7% CA/Logan, and 60% Wor-like; 59% mixed infections) based on a contingency test (P < 0.0001). Whole-genome sequencing (GenBank accessions KT276895 to KT276920 and KX867015 to KX867057) with overlapping primers found that the Wor-like strains included Wor, Colorado and a previously undescribed strain designated Kimberly1. Results confirm a shift from Svr being one of the dominant BCTV strains in commercial sugar beet fields in 2006 to 2007 to becoming undetectable at times during recent years.

Industrial hemp (Cannabis sativa) is an emerging crop in Arizona, with many uses, including fiber, cosmetic products, and health food. In 2020, severe curly top disease outbreaks were observed in several hemp fields in Yuma and Graham Counties, Arizona, where disease incidence and severity were considerably high, up to 100% crop loss occurring in some fields. A wide range of symptoms have been observed at different infection stages and plant growth stages at the time of infection. Early-stage symptoms manifest as light green-to-yellowing of new growth, similar to sulfur or micronutrient deficiency, usually combined with older leaves with dark green "blotchy" mosaic mottling overlaying light green chlorosis. Mosaic mottling of older leaves continues into mid-growth stage and is coupled with more severe yellowing and witch's broom (stunted leaves and shortened internode length of stem) of apical meristematic tissue. Curling and twisting of new leaves have also been observed. Symptoms often appear to be isolated to individual branches, with other branches showing no visual symptoms, often outgrowing and covering affected branches until harvest. Late-stage symptoms include severe leaf curling with or without twisting, continued stunting, and necrosis of yellow leaves, resulting in significant yield reduction. Severely affected plants dwarfed by the virus experienced high mortality rates later into the season, most likely attributed to reduced ability to overcome abiotic stress conditions. These symptoms indicated the likelihood of curly top caused by beet curly top virus (BCTV), which has been recently reported in Colorado. Shoots were collected from 38 symptomatic and nine asymptomatic hemp plants from July to August 2020. Leaves were also collected as a positive control from four chili pepper plants with or without curly top symptoms in Cochise County. Genomic DNA was extracted using a DNeasy Plant Pro Kit (Qiagen, Valencia, CA) according to the manufacturer's instructions. BCTV-specific primers BCTV1 and BCTV2 were used to detect BCTV following a method by Rondon. A 500-bp DNA fragment, indicative of BCTV, was amplified from all symptomatic hemp and chili pepper samples but not from asymptomatic samples. Sequence analysis of this 500-bp DNA fragment revealed 98.99% identity with GenBank accession MK803280, which is a BCTV isolate from hemp identified in Western Colorado. The full-length genomes of BCTV isolates from hemp and chili peppers were generated with additional primers 328F/945R (620 bp), 455F/945R (490 bp), OutR/2213F (1,190 bp), 2609R/1278R (1,340 bp), and BCTV2/2609R (1,890 bp). The complete nucleotide sequence (MW182244) from hemp was 2,929 bp and had 99.35% sequence identity with GenBank accession KX867055, which was a Worland strain of BCTV isolated from an Idaho sugar beet plant. Our hemp BCTV genome sequences shared 96.08% identity with the hemp strain of BCTV from Colorado (MK803280) and 99.50% identity with the BCTV isolate (MW188519) from chili pepper identified in this study. BCTV was reported on outdoor hemp in Western Colorado, in 2020. This is the first report of BCTV in Arizona causing curly top of industrial hemp in the field. In Arizona, BCTV is widespread on many agronomic crops including chili peppers and spread primarily by the phloem-feeding beet leafhoppers: Circulifer tenellus (Hemiptera: Cicadellidae). Due to the wide distribution of beet leafhoppers and abundant range of host plants for the virus, BCTV may become one of the most yield-limiting factors affecting the emerging industrial hemp production systems in Arizona.