Final diagnosis


Stolbur, big bud (Candidatus Phytoplasma solani)

The apex of this Virginia tobacco plant shows shorter internodes and small leaves with irregular margins tending to curve downward. Stolbur
Young, mosaic patterned tobacco leaves tend to curve downwards, this symptom is characteristic of Cucumber mosaic virus (CMV)
In this Virginia plant, the phytoplasma infection induces a proliferation of many axillary buds with short internodes and small leaves. This gives the apex of the plant a “bushy” appearance. Stolbur
Burley tobacco plants, seen in the foreground, are severely infested with the phytoplasma causing stolbur, big bud (<i>Candidatus</i> Phytoplasma solani). This is not the case of dark tobacco plants seen in the backround. The latter, generally hardier plants, are more tolerant to this disease.
Marked yellowing of lower leaves of a Virginia type tobacco. Stolbur
Recently formed leaves are small, their internodes are shorter than those of lower leaves, which indicates slow plant growth. Stolbur
Several leaves of dark tobacco show widespread yellowing or bleaching. <i>Candidatus</i> Phytoplasma solani (stolbur, big bud)
Interveinal yellowing gradually progresses to the entire lamina, a few veins remain green. Stolbur
Discrete vein necrosis on a chlorotic dark tobacco leaf; colour appears slightly metallic. These lesions should not be confused with those caused by necrogenic PVY strains. <i>Candidatus</i> Phytoplasma solani(stolbur, big bud)
After the first frost, affected leaves turn golden yellow. Stolbur
Compared to a normal flower (seen on the right) one can easily observe the impact of stolbur on the flower of an infected plant (left). Stolbur
Flowers of the inflorescence are often small and sterile. Stolbur
The newly formed leaves are small, their tips are curved downwards. Stolbur
The most characteristic symptoms can be observed on axillary shoots, the leaves are small with chlorotic margins tending to curve down on short internodes. Stolbur
These pale tobacco leaves, with thick and boardy tissues come from plants infected by <i>Candidatus</i> Phytoplasma solani (stolbur, big bud).
Several more or less spherical structures in the veins of the phloem are observed by electron microscopy. Phytoplasma causing stolbur
Les <b>phytoplasmes</b> présents dans les vaisseaux du phloème peuvent aussi être détectés grâce des anticorps monoclonaux. Sur la coupe réalisée dans la nervure d'une feuille saine aucune fluorescence n'est observée dans les vaisseaux (a) ; ce n'est pas le cas dans la nervure d'une feuille affectée par le stolbur : une fluorescence bleu-vert est bien visible (b).