Abstract:
In vitro culture of entire or fragmented meristem explants having 0.2
mm, 0.5 mm and 1 mm size and prelevated from the apical bud of vinifera
genotype Feteasca Neagra, was applied in order to eliminate viruses causing
grapevine leafroll and fanleaf.
As far as ultrastructural studies continue to hold a special place in
defining the virus-host plant relationship, and some modifications of the cell
organites may have a diagnostic value, the regenerated plant selection was
made by using ultramicroscopic analysis. The plants regenerated from
fragmented meristematic explants having a dimension of 1 mm presented all
the cells as having thick cytoplasm with a grainy aspect, but also cells
presenting blade-like shapes developing as myelinic shapes, multivesicle
shapes and lots of endoplasmic reticule contours.
Both 80% - 90% of the plants regenerated from entire meristematic
explants of 0.2 mm size prelevated from the apical meristem as well as from the
1st and the 2nd axillary bud of the mother plants infected by the leafroll virus,
and 50%-80% of the plants prelevated from the apical meristem and only from
the 1st axilary bud of the mother plants infected by the fanleaf virus showed
normal ultrastructural aspects characteristic for the virus-free plants.
The plants regenerated from meristematic tissues representing the
apical pitch and a leaf primordial (0.5 mm size) isolated from the apex and
the 1st axillary bud, when fragmented, they showed quite high percentage of
virus-free plants: 20% - 40% for the fanleaf virus and 30% - 60% for the
virus determining leafroll, depending on the genotype. The efficiency of the
method increases by more than 20% when the explants are isolated at the
level of the apex.
Plant regeneration from leaf explants by direct adventive organogenesis
(without differentiation of callus tissue generating genetic variability) induced
the obtention of virus-free plants in a rate of 11.11% - 25% when using leaf
explants of 0.5 and 1 mm, not fragmented. When fragmentation is applied, the
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Universitatea de Ştiinţe Agricole şi Medicină Veterinară Iaşi
efficiency of the method is neatly higher, determining a percentage of virus-free
plants of 100% for the virus causing leafroll.
