A summary

Agrobacterium rhizogenes is known to induce the pro-liferation of rapid growing, highly branching roots (hairy roots) in most dicotyledonous plants. We report here the effect of in vitro infection of Vitis vinifera with two A. rhizogenes strains (b-glucuronidase transgenic A4 and wild type LBA), with regard to an increase of root mass. In vitro-grown V. vinifera explants were infected with two A. rhizogenes strains. Both strains induced a signifi-cant increase in the number of the developed roots, and of their weight and length. Root number was increased by a factor of 2.9 (strain A4) and 2.7 (strain LBA), length in-creased 1.9 and 1.6 times (strains A4 and LBA, respec-tively), while the root weight was more affected by strain A4 (2.8 times increasing) than by LBA strain (1.9 times in-creasing). The transformation status of the developed roots was assessed by two different methods: PCR detection of rolB gene in LBA strain-derived roots and quantification of â-glucuronidase activity in A4 strain-derived roots. K e y w o r d s: Vitis vinifera, Agrobacterium rhizogenes, rooting, in vitro culture