  In this letter we compute energy transfer rates from velocity field to
magnetic field in MHD turbulence using field-theoretic method. The striking
result of our field theoretic calculation is that there is a large energy
transfer rate from the large-scale velocity field to the large-scale magnetic
field. We claim that the growth of large-scale magnetic energy is primarily due
to this transfer. We reached the above conclusion without any linear
approximation like that in $\alpha$-dynamo.
