Persistent, and Asymptomatic Viral Infections and Whitefly-Transmitted Viruses Impacting Cantaloupe and Watermelon in Georgia, USA

Abstract

Cucurbits in Southeastern USA have experienced a drastic decline in production over the years due to the effect of economically important viruses, mainly those transmitted by the sweet potato whitefly (Bemisia tabaci Gennadius). In cucurbits, these viruses can be found as a single or mixed infection, thereby causing significant yield loss. During the spring of 2021, surveys were conducted to evaluate the incidence and distribution of viruses infecting cantaloupe (n = 80) and watermelon (n = 245) in Georgia. Symptomatic foliar tissues were collected from six counties and sRNA libraries were constructed from seven symptomatic samples. High throughput sequencing (HTS) analysis revealed the presence of three different new RNA viruses in Georgia: cucumis melo endornavirus (CmEV), cucumis melo amalgavirus (CmAV1), and cucumis melo cryptic virus (CmCV). Reverse transcription-polymerase chain reaction (RT-PCR) analysis revealed the presence of CmEV and CmAV1 in 25% and 43% of the total samples tested, respectively. CmCV was not detected using RT-PCR. Watermelon crinkle leaf-associated virus 1 (WCLaV-1), recently reported in GA, was detected in 28% of the samples tested. Furthermore, RT-PCR and PCR analysis of 43 symptomatic leaf tissues collected from the fall-grown watermelon in 2019 revealed the presence of cucurbit chlorotic yellows virus (CCYV), cucurbit yellow stunting disorder virus (CYSDV), and cucurbit leaf crumple virus (CuLCrV) at 73%, 2%, and 81%, respectively. This finding broadens our knowledge of the prevalence of viruses in melons in the fall and spring, as well as the geographical expansion of the WCLaV-1 in GA, USA.

Keywords: Georgia; USA; cantaloupe; cucumis melo amalgavirus (CmAV1); cucumis melo cryptic virus (CmCV); cucumis melo endornavirus (CmEV); persistent virus; watermelon; watermelon crinkle leaf-associated virus 1 (WCLaV-1).

Figure 1

Map of Georgia showing counties from which melon samples were collected during spring 2021 survey.

Figure 2

Symptoms observed on the field during the survey include: on watermelon (A–C), leaf crinkling and bunchy top with upward curling appearance of young leaves (A), crinkling of young leaves with mild yellowing (B), severe interveinal chlorosis of the leaf (C). On cantaloupe, yellowing and interveinal chlorosis on the older leaf (D). Watermelon (A,B) and cantaloupe (D) was collected in spring 2021 and watermelon (C) was collected in fall 2019.

Figure 3

Read coverage maps of the virus genomes detected by HTS of small RNAs of symptomatic watermelon and cantaloupe from Georgia. Watermelon crinkle leaf-associated virus 1 (WCLaV-1) (A), cucumis melo amalgavirus 1 (CmAV1) (B), cucumis melo endornavirus (CmEV) (C), and cucumis melo cryptic virus (CmCV) (D). Genome positions of the virus are presented to scale above the histograms and the coverage in number of reads is represented on the Y-axis. Within the specified aggregation bucket, the colors mean: the maximum, average, and the minimum coverage values (read counts), from top to bottom.