Differential Seasonal Prevalence of Yellowing Viruses Infecting Melon Crops in Southern California and Arizona Determined by Multiplex RT-PCR and RT-qPCR

Abstract

Viruses transmitted by the whitefly (Bemisia tabaci) are an increasing threat to cucurbit production in the southwestern United States as well as many other cucurbit production regions throughout the world. The crinivirus, cucurbit yellow stunting disorder virus (CYSDV), has severely impacted melon production in California and Arizona since its introduction to the region in 2006. Within the past few years, another crinivirus, cucurbit chlorotic yellows virus (CCYV), and the whitefly-transmitted ipomovirus, squash vein yellowing virus (SqVYV) were found infecting melon plants in California’s Imperial Valley as well. Both CYSDV and CCYV, as well as an aphid transmitted polerovirus, cucurbit aphid-borne yellows virus (CABYV), occur together in the region and produce identical yellowing symptoms on cucurbit plants. Mixed infections of these four viruses both in the Sonoran Desert and other regions pose challenges for disease management and efforts to develop resistant varieties. A multiplex single-step RT-PCR method was developed that differentiates these viruses from one another, and this was used to determine the prevalence and distribution these viruses in melon samples collected from fields in the Sonoran Desert melon production region of California and Arizona, USA during spring and fall melon seasons from 2019 through 2021. TaqMan probes were also developed, optimized, and applied in a single-step multiplex RT-qPCR to quantify titers of these four viruses in plant samples, which frequently carry mixed infections. Results of the multiplex RT-PCR analysis demonstrated that CYSDV is the predominant virus during the fall season, whereas CCYV was by far the most prevalent virus during spring seasons each year. Multiplex RT-qPCR was used to evaluate differential accumulation and spatio-temporal distribution of viruses within plants and suggested differences in competitive accumulation of CCYV and CYSDV within melon. This study also provides the first official report of SqVYV in Arizona, USA, and offers an efficient method for virus detection and quantification for breeding and disease management in areas impacted by cucurbit yellowing viruses.

Virome Profiling, New Virus Identification and the Prevalence and Distribution of Viruses Infecting Chieh-Qua (Benincasa hispida Cogn. var. chieh-qua How) in China

“…In this study, a putative novel crinivirus was identified and molecularly characterized. The closest relative of CuCV appears to be CYSDV, a Bemisia-tabaci -transmitted crinivirus causing extensive infections of cucurbit crops in many warm and temperate production areas [ 29 , 30 , 31 , 32 , 33 ]. The taxonomy of CuCV was first determined based on the low complete genome identity (65–69%) with CYSDV isolates compared to the 99% intraspecific similarity of CYSDV isolates ( Tables S7 and S8 ), despite the extensive and discontinuous geographical distribution and different years of collection.…”

Incidence and genetic diversity of cucurbit viruses in the Spanish Mediterranean area

“…In 2011 the crinivirus cucurbit chlorotic yellows virus (CCYV) was first reported in Europe, specifically in Greece, causing symptoms similar to those produced by CYSDV (Orfanidou et al., 2014). Even though CCYV has spread to other Mediterranean countries (Maachi et al., 2022), it has not yet been as problematic in open field conditions as it is in the United States, where both CCYV and CYSDV have been detected in a high percentage of samples tested on both the East and West Coasts (Kavalappara et al., 2021; Mondal et al., 2023). Another whitefly‐transmitted virus that causes severe economic losses in greenhouse and open‐field cucurbit crops is the tomato leaf curl New Delhi virus (ToLCNDV), that was first reported in Europe in 2012 in Spain (Juárez et al., 2014) and is rapidly spreading.…”