'Plant Breeding: Sustaining the Future' Abstracts of the XVIth EUCARPIA Congress, Edinburgh, Scotland, 10-14 September 2001 MOLECULAR BREEDING OF FRUIT TREES S.V. DOLGOV Branch of Shemyakin Institute of Bioorganic Chemistry RAS, 142292 Pushchino Moscow Region, Russia

Most research to date has focused on genes conferring resistance to viruses, bacteria, insects and fungi. However, attention has also been given to genes that regulate such parameters as freezing tolerance of fruit taste.  For fruit taste improvement of temperature fruit crops - apple, pear, the gene supersweet protein thaumatin II from Thaumatoccoccus danielli was used in our research.  The introduction of thaumatin gene was confirmed by PCR analysis.  The high thaumatin expression was observed in callus tissues and lower one in leaves of greenhouse plants of apple and pear.  The herbicides are widely used in nurseries and orchards.  Herbicide resistant fruit rootstock is a new way conferring selectivity and enhancing fruit crop safety and production.  The bar gene cloned in "Bioengineering Centre" RAS have been used in our research for obtaining phosphinotricine-resistance of apple and pear rootstocks.  Developed transformation protocols allowed us to obtain more than 20 transgenic plants of semi-dwarf rootstock N545 and clonal one pear GP217.  Some of them demonstrated resistance to commercial herbicide "Basta" as in vitro as in soil conditions. For the horticultural plants protection against fungal and microbial attack the plant defensins genes (PD) have been transferred to pear, apple and strawberry.  Based on previously developed transformation methods of the PD gene from R.sativus was transferred to clonal apple and rootstock N545, pear variety Burakovka by using different agrobacterial vector systems.  Obtained plant lines - more than 30 apple and about 70 pear successfully rooted on high antibiotic media and some of that demonstrated high NPT activity in greenhouse growing plants.  PD gene introduction in genomes has been confirmed by PCR analysis.  In most of these lines demonstrated PD gene expression detected by Western blot analysis.  The tests for their resistance to some phytopathgens are in progress now.  Transgenic apple, pear and strawberry plants expressed thaumatin, defensin and bar genes are tested in the field conditions from 2000 year.