Detection of Two Pospiviroid Species Affecting Tomato and Pepper Crops in Saudi Arabia

During the growing season 2018-2019, a total of 199 tomato and 21 pepper asymptomatic and symptomatic samples were collected from different major regions of Saudi Arabia. Using the general Norgen Kit and universal Pospi1-RE/Pospi1-FW primers for Pospiviroid RT-PCR detection, only seven tomato samples and three pepper samples were positive, which amplified the PCR products with the expected sizes of ~364 bp and /~350 bp respectively, confirming the presence of at least one of the nine Pospiviroid species. The PCR amplified products were sent for sequencing, and the results confirmed the presence of tomato apical stunt viroid (TASVd) and pepper chat fruit viroid (PCFVd). However, further confirmation was conducted using specific primers for TASVd and PCFVd that amplify the complete genome. One positive TASVd Saudi isolate was selected to evaluate the severity and symptom responses to mechanical inoculation of four tomato cultivars that are often grown in greenhouses. According to the data obtained, each cultivar exhibited a significant change in each metric. The studied cultivars' plant heights did not differ significantly from one another. The greatest decrease in vegetative dry weight (39.3%) was observed in the Newton cultivar; with just a 6% decrease in comparison to the healthy controls, the Alindi cultivar was the least impacted. With a 90.2% decrease in fruit output when compared to its untreated control, the Newton cultivar was the most impacted; meanwhile, with a 49.1% decrease in fruit output, the Irit cultivar was the least impacted. The infection of viroids and their economic impact on commercial tomato cultivars have been discussed.