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

Abstract

Knowledge about the host range and genetic structure of emerging plant viruses provides insights into fundamental ecological and evolutionary processes, and from an applied perspective, facilitates the design and implementation of sustainable disease control measures. Tomato leaf curl New Delhi virus (ToLCNDV) is an emerging whitefly transmitted begomovirus that is rapidly spreading and inciting economically important diseases in cucurbit crops of the Mediterranean basin. Genetic characterization of the ToLCNDV Mediterranean populations has shown that they are monophyletic in cucurbit plants. However, the extent to which other alternative (cultivated and wild) hosts may affect ToLCNDV genetic population structure and virus prevalence remains unknown. In this study a total of 683 samples from 13 cultivated species, and 203 samples from 24 wild species from three major cucurbit-producing areas of Spain (Murcia, Alicante and Castilla-La Mancha) from five cropping seasons (2012–2016) were analyzed for ToLCNDV infection. Except for watermelon, ToLCNDV was detected in all cultivated-cucurbit species as well as in tomato. Among weeds, Ecballium elaterium, Datura stramonium, Sonchus oleraceus , and Solanum nigrum were identified as alternative ToLCNDV plant hosts, which could act as new potential sources of virus inoculum. Furthermore, we performed full-genome deep-sequencing of 80 ToLCNDV isolates from different hosts, location and cropping year. Our phylogenetic analysis supports a Mediterranean virus population that is genetically very homogeneous, with no clustering pattern, and clearly different from Asian virus populations. Additionally, D. stramonium displayed higher levels of within-host genetic diversity than cultivated plants, and this variability appeared to increase with time. These results suggest that the potential ToLCNDV adaptive evolution occurring in wild plant hosts could serve as a source of virus genetic variability, thereby affecting the genetic structure and spatial-temporal dynamics of the viral population.

Overview of Biotic Stresses in Pepper (Capsicum spp.): Sources of Genetic Resistance, Molecular Breeding and Genomics

“…The begomovirus, Tomato leaf curl New Delhi virus (ToLCNDV), represents an important constraint to tomato production, in the Indian sub-continent. In recent years the virus has been rapidly spreading into several countries of the Mediterranean basin causing significant economic losses on cucurbit and tomato [188]. Recently, it has been recovered in Italy in pepper plants showing yellowing and leaf curling [189].…”

Pest categorisation of tomato leaf curl New Delhi virus

“…the pest has to be eradicated immediately if detected. However, the Panel notices the frequent report of outbreaks in Spain since 2013 (Table 3), and information from the literature suggesting that it might be more widespread in open field and in the environment than officially reported (Ju arez et al, 2019;Panno et al, 2019). 2017Source: EPPO GD, accessed on 24/2/2020.…”

“…A monogenic resistance has been reported in a breeding line of sponge gourd (Islam et al, 2011) while in melon, five accessions were found to be resistant to ToLCNDV (Romay et al, 2019). In potato, the Indian cultivar Kufri Bahar is reported tolerant to the disease (Jeevalatha et al, 2017). Breeding efforts are ongoing and this option is seen as a major strategy over the long run, while its current applicability is still extremely limited Impact • In some hosts, symptoms may be confused with those caused by other begomoviruses;…”

A Major QTL Located in Chromosome 8 of Cucurbita moschata Is Responsible for Resistance to Tomato Leaf Curl New Delhi Virus

“…Rich], smooth sowthistle (Sonchus oleraceus L.), false daisy [Eclipta prostrata (L.) L.], and apple of Sodom [Calotropis procera (Aiton) Dryand.] (Haider et al, 2006;Moriones et al, 2017;Zaidi et al, 2017;Juárez et al, 2019) have been found to be hosts of the virus, acting as reservoirs during the whole year.…”