Which method was used to transfer the streptomycin resistance gene from $Nicotiana$ $tabacum$ to $Nicotiana$ $sylvestris$?

Virus-free plants can be obtained through$-$

The main technique involved in agricultural biotechnology is called

Who proposed the idea that every plant cell is totipotent and can be used for the in vitro growth of plants?

For which purpose are plants developed through the plant tissue culture method used?

In tissue culture experiments using tobacco callus,it was observed that when the culture medium contains $2 \ ppm$ of $IAA$ and $2 \ ppm$ of kinetin,an undifferentiated mass of callus is produced. If the ratio of kinetin to $IAA$ is increased,what will happen?