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

Abstract

The tomato leaf curl New Delhi virus (ToLCNDV) (genus Begomovirus, family Geminiviridae) represents an important constraint to tomato production, as it causes the most predominant and economically important disease affecting tomato in the Indian sub-continent. However, in recent years, ToLCNDV has been fast extending its host range and spreading to new geographical regions, including the Middle East and the western Mediterranean Basin. Extensive research on the genome structure, protein functions, molecular biology, and plant–virus interactions of ToLCNDV has been conducted in the last decade. Special emphasis has been given to gene silencing suppression ability in order to counteract host plant defense responses. The importance of the interaction with DNA alphasatellites and betasatellites in the biology of the virus has been demonstrated. ToLCNDV genetic variability has been analyzed, providing new insights into the taxonomy, host adaptation, and evolution of this virus. Recombination and pseudorecombination have been shown as motors of diversification and adaptive evolution. Important progress has also been made in control strategies to reduce disease damage. This review highlights these various achievements in the context of the previous knowledge of begomoviruses and their interactions with plants.

Emergence of tomato leaf curl New Delhi virus in Italy: estimation of incidence and genetic diversity

“…that ≥91% and ≥94% nucleotide sequence identity account for begomovirus species and strain demarcation, respectively (Brown et al ., ). Therefore, these isolates constitute a new strain of this virus, for which the name ES (ToLCNDV‐ES) was proposed (Moriones et al ., ). Evolutionary relationships among ToLCNDV sequences used in this study showed that all the Italian isolates are closely related to those from Spain, Tunisia and Morocco and thus a common origin can be assumed for these isolates, identifiable in ToLCNDV‐ES.…”

“…Evolutionary relationships among ToLCNDV sequences used in this study showed that all the Italian isolates are closely related to those from Spain, Tunisia and Morocco and thus a common origin can be assumed for these isolates, identifiable in ToLCNDV‐ES. As ToLCNDV rapidly spread in a few years within the Mediterranean area, the low level of variability found among isolates supports the hypothesis of the founder effect associated with a population bottleneck during the spread to this new area (Moriones et al ., ). As reported by different authors (Juárez et al ., ; Mnari‐Hattab et al ., ; Luigi et al ., ; Panno et al ., ; Moriones et al ., ), ToLCNDV in the Mediterranean basin found zucchini squash as its elected host.…”

“…As ToLCNDV rapidly spread in a few years within the Mediterranean area, the low level of variability found among isolates supports the hypothesis of the founder effect associated with a population bottleneck during the spread to this new area (Moriones et al ., ). As reported by different authors (Juárez et al ., ; Mnari‐Hattab et al ., ; Luigi et al ., ; Panno et al ., ; Moriones et al ., ), ToLCNDV in the Mediterranean basin found zucchini squash as its elected host. In these countries, this cucurbit is intensively cultivated during the entire year in the open field (summer crops) as well as in the greenhouse (autumn‐spring crops).…”

“…The prolonged presence of this host, as well as the mild climate favouring overlapping cycles of the vector, have facilitated the rapid spread of the virus. It has been demonstrated that ToLCNDV-ES is probably the result of genetic recombination between a ToLCNDV-type isolate and other begomoviruses (Moriones et al, 2017). Recombination exchanges at the intraspecies and interspecies level, due to mixed infection in the same host, are frequent in begomoviruses and considered more significant than mutation as a driving force in the evolution of begomoviruses, by increasing genetic variability and allowing adaptation to new agroecological contexts, including novel hosts (Davino et al, 2009(Davino et al, , 2012.…”

Pest categorisation of non‐EU viruses and viroids of potato

“…However, these three viruses produced consistent symptoms and have been shown to be transmissible. Begomoviruses are phloem-limited viruses and therefore generally considered not seed-transmitted, with a few possible exceptions (Mink, 1993;Bos, 1999) Yes Reported to be persistently transmitted by Bemisia tabaci (Rosen et al, 2015;Moriones et al, 2017) Genus, Virus Acronym Biology of the pests All viruses considered in the present categorisation are transmitted by vegetative propagation (via tubers).…”