Transgenic plants using the above technique have been obtained in many cases including soybean, tobacco, maize, rice, wheat, etc. Transient expression of genes transferred in cells by this method has also been observed in onion, maize, rice and wheat. During 1990s, there was no other gene transfer approach, which met with' so much of enthusiasm. Consequently considerable investment was also made in experimentation and manpower for development of this technique. The advantages of this method over microinjection include the following: (i} thousands of particles are accelerated at the same time, causing multiple hits resulting in transfer of genes into many cells simultaneously; (ii) since intact cells can be used, some of the difficulties encountered with the use of protoplasts are automatically circumvented; (iii) the method is universal in its application, so that cell type, size and shape or the presence/absence of cell walls do not significantly alter its effectiveness.
In view of this, particle bombardment method using microprojectiles was used in a variety of plant species, particularly the cereals. The method was also used successfully for transfer of genes into the plastid genome. However, the emphasis on 'the use of particle gun decreased towards the end of 20th century, due to the success achieved in cereals with Agrobacterium mediated gene transfer.