Main symptoms

Very many strains of zucchini ( yellow mosaic virus Zucchini yellow mosaic virus , ZYMV) causing quite different symptoms were reported from the first description of this virus. In addition, symptoms can vary in intensity depending on the season (they are usually more severe in summer), the species or variety infected. It should be noted that more accentuated symptoms may be observed in the event of co-infection with other viruses (synergy), and in particular with the cucumber mosaic virus  (CMV).

In melons, the first symptoms observed on foliage are thinning of the veins, yellowing and stunted growth (Figure 1). The internodes generally remain very short and the new leaves are very deformed: abnormal shapes, dark green blisters or blisters (figures 2 to 4), enations * (figure 5). The plant is blocked and takes on the appearance of a bush. In late infection the shoots show an upright habit.

Strains recently detected in France, close to Asian strains, cause less marked symptoms: a slightly deforming mosaic is observed on the foliage, but there is no blocking of the growth of the plant.

In addition, certain strains of ZYMV are responsible in a large number of commercial varieties of melon (possessing a particular gene, the gene Fn ) for very rapid wilting of the infected plant (Figures 6 and 7). The latter then dries up completely in a few days. This symptom may sound like an attack by Fusarium or another vascular pathogen, but in this case the vessels of the neck or stem remain intact.

On fruits , symptoms vary greatly depending on the virus strain and varietal susceptibility. One can observe mosaics (figures 8 to 10), blisters (figure 12), bursts (figure 12) of the fruits and sometimes deformation of the seeds. The flesh may be discolored and remain tough (Figure 13). Such fruits can obviously not be marketed

* An enation is a leaf deformation leading to the appearance of small cups on the upper or lower surface of the leaf blade.