The description of ToLCNDV was carried out in the 1990s in Indian territory, affecting tomato crops, where it became one of the main phytopathogens (Paddidan et al., 1995). In recent years, the number of hosts and crop families has significantly increased, extending to cucurbit crops and other Solanaceae, emerging as a problem in countries such as Pakistan, Bangladesh, Thailand, Indonesia, and Iran.

In Spain, it was first identified in mid-2012 in zucchini crops in the Murcia region (Juárez et al., 2014), and later identified in Almería and Málaga in both protected and open-field crops. Among the twenty-four most affected crops, melon and zucchini stand out.

The accelerated spread of this virus to Mediterranean coastal areas is possibly attributed to the overlapping production cycles of susceptible monocultures in the summer, where temperatures favor and accelerate the life cycles of Bemisia tabaci throughout the Mediterranean region. This whitefly is the responsible vector for its transmission.



Studies conducted on the genomic sequence of Spanish isolates of ToLCNDV reveal the existence of a new strain, designated as ToLCNDV-ES, which may have evolved through recombination (Fortes et al., 2016; Ruiz et al., 2017a).

These isolates also exhibit a high sequence identity and form a homogeneous group, likely due to a single recent introduction event. This is a typical phenomenon when a plant becomes a new host. Therefore, it can be concluded that the Spanish population (and possibly the entire European and North African population) of ToLCNDV has been constituted by a single isolate (Zaidi et al., 2017).



In general, the New Delhi virus causes pronounced mosaic with chlorotic effects on upper and middle leaves, while younger leaves exhibit curling towards the underside or upper side.

Specifically in melon, on young leaves, a puckering occurs, resulting in curling towards the underside, with noticeable interveinal and marginal yellowing. Simultaneously, a loss of plant vigor can be observed due to shortened internodes.

Regarding symptoms in advanced fruiting stages, the fruit may exhibit cracking and depressions.



As we have stated, its main transmission occurs through the whitefly, Bemisia tabaci, in a persistent and circulative manner (Sohrab et al., 2003).
Traditionally, the whitefly present in the peninsula has been composed of cryptic invasive species MEAM1 from the Middle East and MED (Mediterranean), known as biotypes B and Q, although recent phylogenetic studies on cucurbit crops from different populations in southeastern Spain indicate mostly Mediterranean Med-Q1.
However, this vector is not limited to this transmission alone; it can also spread, in addition to the New Delhi virus, the Cucumber Vein Yellowing virus (CVYV).



The challenges faced by open-field cultivation of cucurbits, particularly melons, are evident compared to greenhouse cultivation. In greenhouses, measures of hermeticity are being implemented, resulting in much lower presence or arrival of the vector to the plants, with an average incidence of only 1 in every 15 plants in this cultivation area in Almería, where protected cultivation is predominant due to its cycle. Additionally, it boasts greater adaptability for the installation of Amblyseius swirskii, a natural predator of the whitefly.

Regarding measures to reduce incidences and severity in open-field cultivation, some general practices to highlight include:

1. Use of agrotextile covers: This practice is a good measure to protect the early stages of outdoor cultivation, especially during the warmer months. These covers should be sufficiently wide and properly sealed along the sides. They can also be placed inside greenhouses when they lack suitable mesh to prevent the entry of the vector.

2. Maintain adequate vector control throughout the cultivation period: This is a crucial measure that farmers should implement, either through natural enemies or integrated chemical treatments.

3. Removal of contaminated crops: If there are very high populations of vector insects (aphids and whiteflies) and plants showing symptoms of this and other viruses, it is advisable to treat with an adulticide insecticide or with an insecticide plus a desiccant, and remove the crop by burying it or removing it from the farm in a controlled manner.

4. Implement preventive treatments with elicitors to reduce or alleviate the degree of incidence or severity of the virus.

5. Avoid placing new crops next to contaminated crops.

6. Never overlap different crop cycles.

7. Conduct biofumigation or biosolarization if the soil and conditions allow.

8. If farms do not have effective enclosures or are outdoors, it is crucial to ensure that all farmers implement proper vector control using integrated products until the end of the crop. This promotes biological control and enables quick and adequate removal of diseased plants. It’s also essential to keep plots clean of residues from previous plantings and weeds that could harbor and multiply the virus and vector between crop cycles.



6.1. Indirect Effectiveness

Chitosan, with its diverse properties, is an antiviral agent that can suppress viral infections in plants. Its efficacy depends on factors such as the degree of polymerization, deacetylation and positive charge, as well as chemical modifications. It can inactivate viral particles and prevent bacteriophage multiplication in infected cultures. By mimicking plant contact with pathogens, it induces protective reactions, limiting viral spread and promoting systemic acquired resistance. Efficacy varies according to host-virus combination, concentration and method of application.

In addition, chitosan activates defense responses in plants, such as lignin and callose synthesis, enzyme production and pathogenicity-related proteins, strengthening resistance to viral infections.

6.2. Direct Effectiveness

The binding of chitosan with DNA and the inhibition of mRNA synthesis occur through the penetration of chitosan into the nucleus of microorganisms and interference with mRNA synthesis and protein synthesis (Sudarsham et al., 1992).


6.3. Cultisano

CULTISANO is a liquid solution containing chitosan (poly-D-glucosamine), a natural polymer derived from the exoskeletons of crustaceans, combined with amino acids obtained through enzymatic hydrolysis of plant proteins.