Natural Occurrence of Tomato leaf curl New Delhi virus in Iranian Cucurbit Crops

Abstract

The main areas for field-grown vegetable production in Iran were surveyed during the years of 2012–2014 to determine the occurrence of begomoviruses infecting these crops. A total of 787 leaf samples were collected from vegetables and some other host plants showing virus-like symptoms and tested by an enzyme-linked immunosorbent assay (ELISA) using polyclonal antibodies produced against Tomato yellow leaf curl virus (TYLCV). According to the ELISA results, 81 samples (10.3%) positively reacted with the virus antibodies. Begomovirus infections were confirmed by polymerase chain reaction (PCR) using previously described TYLCV-specific primer pair TYLCV-Sar/TYLCV-Isr or universal primer pair Begomo-F/Begomo-R. The PCR tests using the primer pair TYLCV-Sar/TYLCV-Isr resulted in the amplification of the expected fragments of ca. 0.67-kb in size for ELISA-positive samples tested from alfalfa, pepper, spinach and tomato plants, confirming the presence of TYLCV. For one melon sample, having a week reaction in ELISA and no reaction in PCR using TYLCV-specific primers, the PCR reaction using the primer pair Begomo-F/Begomo-R resulted in the amplification fragments of the expected size of ca. 2.8 kb. The nucleotide sequences of the DNA amplicons derived from the isolate, Kz-Me198, were determined and compared with other sequences available in GenBank. BLASTN analysis confirmed the begomovirus infection of the sample and showed 99% identities with Tomato leaf curl New Delhi virus (ToLCNDV); phylogenetic analysis supported the results of the database searches. This study reports the natural occurrence of TYLCV in different hosts in Iran. Our results also reveal the emergence of ToLCNDV in Iranian cucurbit crops.

Natural Hosts and Genetic Diversity of the Emerging Tomato Leaf Curl New Delhi Virus in Spain

“…In this sense, ToLCNDV has been described to affect a wide spectrum of plant species, such as aubergine, pepper, potato, tomato, lettuce, celery, bean and broad bean in the Indian subcontinent (Usharani et al, 2004; Pratap et al, 2011; Kushwaha et al, 2015). However, in the Mediterranean countries, ToLCNDV had been only identified infecting cucurbit and tomato plants (Juárez et al, 2014; Mnari-Hattab et al, 2015; Fortes et al, 2016; Panno et al, 2016; Yazdani-Khameneh et al, 2016; Parrella et al, 2017; Sifres et al, 2017; Zaidi et al, 2017), and its extent in further plant hosts was unknown. In this study, ToLCNDV appeared to infect cultivated cucurbit plants and tomato plants as well (see Table 1), although this was not the case in watermelon plants, being an interesting open question.…”

“…Among them, whitefly transmitted virus diseases have been constantly emerging and are a major concern for agriculture (Navas-Castillo et al, 2011, 2014). As an example, outbreaks of tomato leaf curl New Delhi virus (ToLCNDV; genus Begomovirus , family Geminiviridae ) have recently emerged in the cucurbit crops of the Mediterranean basin (Spain, Italy, Tunisia and Morocco), indeed compromising cucurbit productivity and quality (Juárez et al, 2014; Mnari-Hattab et al, 2015; Fortes et al, 2016; Panno et al, 2016; Yazdani-Khameneh et al, 2016; Parrella et al, 2017; Sifres et al, 2017; Zaidi et al, 2017). However, despite the efforts conducted for the control of ToLCNDV diseases, no resistant cultivars to ToLCNDV infection have been identified yet (Sáez et al, 2016).…”

“…This virus is limited to the plant phloem and is transmitted in a circulative persistent manner by the whitefly Bemisia tabaci (Fondong, 2013; Zaidi et al, 2017), although it should be noted that experimental host plants have also been infected by mechanical inoculation (Ruiz et al, 2017). ToLCNDV has a wide host range with 43 different plant species identified thus far (Pratap et al, 2011; Sayed et al, 2013; Kushwaha et al, 2015; Yazdani-Khameneh et al, 2016; Zaidi et al, 2016, 2017; Figàs et al, 2017; Ruiz et al, 2017), mainly belonging to the Solanaceae and Cucurbitaceae families, which comprise economically important crops such as potato (Usharani et al, 2004) and aubergine (Pratap et al, 2011), as well as to several weed species. However, since the emergence of ToLCNDV in some Mediterranean countries, it has only been described to infect cucurbit and tomato plants (Juárez et al, 2014; Mnari-Hattab et al, 2015; Fortes et al, 2016; Panno et al, 2016; Yazdani-Khameneh et al, 2016; Sifres et al, 2017; Zaidi et al, 2017), while other plant hosts can also be involved in the distribution and prevalence of this virus (Ruiz et al, 2017).…”

Tomato Leaf Curl New Delhi Virus: An Emerging Virus Complex Threatening Vegetable and Fiber Crops

“…However, in recent years, ToLCNDV has been fast extending its host range and spreading to new geographical regions. From 2012 a westward spread of this pathogen has occurred, with reports from Iran in the Middle East [ 6 ] and detection for the first time in the western Mediterranean Basin, with severe disease outbreaks associated with ToLCNDV infections in greenhouse and open-field cucurbit crops of Spain [ 7 ]. Moreover, further spread has occurred, with recent reports of ToLCNDV in Tunisia infecting cucurbits (cucumber, Cucumis sativus ; melon, Cucumis melo ; zucchini squash, Cucurbita pepo ) and in Italy, infecting zucchini squash, with isolates closely related to those detected in Spain [ 8 , 9 ].…”

“…At the later stages of the infection, plants appear stunted with shortened internodes and show impaired fruit setting, leading to complete crop loss [ 4 ]. In cucurbits, leaf distortion mosaic diseases are caused by ToLCNDV [ 6 , 7 , 8 , 9 , 10 ]. Satellite DNAs may co-exist with ToLCNDV in natural infections and can modulate its pathogenesis, including its host range (see below).…”