Bt in Bt cotton stands for Bacillus thuringienesis and is a pest-resistant transgenic plant. The transgenic Brassica napus seeds are a source of hirudin which is used as an anti-blood coagulating substance. Flavr savr tomato is a transgenic plant in which the shelf-life of tomato is increased by inhibiting the production of fruit ripening hormone polygalacturonase using the mRNA silencing technique. Somatic hybridization is a cull fusion technique involving the fusion of two complete plant cells carrying desired genes.