FATE OF TRANSFORMED TRICHODERMA-HARZIANUM IN THE PHYLLOPLANE OF TOMATO PLANTS

A propiconazole-resistant Trichoderma harzianum strain with high phyll oplane survival capability was transformed with the E. coli hygromycin B phosphotransferase gene (hph), coding for hygromycin B resistance. Four transformants were analysed for survival ability on the phyllopla ne of tomato plants grown under glasshouse conditions in comparison wi th their prototype and a yellow, hygromycin B-sensitive mutant. Over 2 weeks, the four transformants showed higher survival rates in compari son with the wildtype strain. The yellow mutant TF3/973 did not signif icantly differ in survival from the transformants. Both hygromycin B r esistance and mitotic stability of transformants were evaluated during growth in vitro and after reisolation from tomato phylloplane. Hybrid ization patterns with the complete plasmid indicated that all four tra nsformants were mitotically stable after several rounds of vegetative growth without selective pressure and during 2 weeks on tomato plants. None of the transformants had lost the ability to grow in the presenc e of both propiconazole and hygromycin B after growth under the same c onditions. The results are discussed in relation to risk assessment of the release of transgenic fungi.