Crops
Viral symptoms similar to mosaics
In addition to typical mosaic symptoms presented in the introduction of Leaf mosaics, other viral symptoms can be observed on tobacco (several examples by pictures):
- various abnormal colours (figure 1) like pseudo-mosaics,caused by CMV and TMV, but also PVY that causes rather vein clearing. These three viruses sometimes cause more or less regular darkening of lamina areas located along the veins ("veinmottling", "vein banding").
- vein necrosis (figure 2) is mainly caused by PVY, but also by CMV,some necrotic strains of which are also responsible for localised brown necrosis of midrib and /or of the secondary veins ("vein necrosis").
- there are discrete comma-shaped, white to beige patterns, between or near the veins ("etch"), due to TEV (figure 3) and PVY ; these patterns occur also on genotypes resistant to root-knot nematodes, and to CMV.
- spots or rings (figure 4); chlorotic spots are due to PVY, but when these spots form rings, they may be caused by CMV, and also PVY. When the concentric rings are irregular, yellow and necrotic ("ringspot"), then TRSV should be suspected.
- fairly large, bright yellow to white ("line pattern") rings and /or curved lines are associated with CMV or AMV (figure 5).
- first chlorotic, then necrotic (figure 6) patterns may be induced by two viruses (AMV, CMV). They may induce patterns that follow partially and regularly the contours of the veins looking like "oakleaf". CMV is sometimes responsible for other type of interveinal patterns.
- when leaves are distorted, blistered, more slender or sometimes filiform, you may suspect CMV and TMV. In this case, we recommend you to have a look at the comments made on different viruses in the Abnormal leaf size and shape section, as well as those in the section of Abnormal leaf shape.
- various abnormal colours (figure 1) like pseudo-mosaics,caused by CMV and TMV, but also PVY that causes rather vein clearing. These three viruses sometimes cause more or less regular darkening of lamina areas located along the veins ("veinmottling", "vein banding").
- vein necrosis (figure 2) is mainly caused by PVY, but also by CMV,some necrotic strains of which are also responsible for localised brown necrosis of midrib and /or of the secondary veins ("vein necrosis").
- there are discrete comma-shaped, white to beige patterns, between or near the veins ("etch"), due to TEV (figure 3) and PVY ; these patterns occur also on genotypes resistant to root-knot nematodes, and to CMV.
- spots or rings (figure 4); chlorotic spots are due to PVY, but when these spots form rings, they may be caused by CMV, and also PVY. When the concentric rings are irregular, yellow and necrotic ("ringspot"), then TRSV should be suspected.
- fairly large, bright yellow to white ("line pattern") rings and /or curved lines are associated with CMV or AMV (figure 5).
- first chlorotic, then necrotic (figure 6) patterns may be induced by two viruses (AMV, CMV). They may induce patterns that follow partially and regularly the contours of the veins looking like "oakleaf". CMV is sometimes responsible for other type of interveinal patterns.
- when leaves are distorted, blistered, more slender or sometimes filiform, you may suspect CMV and TMV. In this case, we recommend you to have a look at the comments made on different viruses in the Abnormal leaf size and shape section, as well as those in the section of Abnormal leaf shape.
Figure 1
Figure 2
Figure 3
Figure 4
Figure 5
Figure 6