Simply speaking the large-scale agricultural countries Mahesh i.e. Brazil, the US, Australia and Canada. Though there are interesting positions in Europe too but the work there is multidisciplinary and there are not as many positions for plant biotechnology as in the countries I mentioned before (still you can check the ones in Germany) The States has many open positions advertised lately, check them out.
The multinationals (Syngenta, Monsanto, Indigo AG etc.) spread their research projects around the world depending on their convenience.
Local companies and research centers (i.e. Donald Danforth PSC) investing in applied research are concentrated in USA, Australia, Canada, Brazil, China, India and Netherlands.
Some of the best research institutes (i.e. Max Planck, EMBL, INRA etc.) and universities (i.e. WUR, ETH, BOKU etc. ) are in Europe, but the applied research is still restricted by the laws regarding biotechnology.