  An analysis of type Ia supernova (SNIa) events in early type galaxies from
Evans et al (1989) database provides strong evidence that the rate of type Ia
supernovae (SNe) in radio-loud galaxies is about 6 times higher than the rate
measured in radio-quiet galaxies, i.e. SNIa-rate$(radio-loud
galaxies)=0.47^{+0.23}_{-0.15} h^2_{50}$ SNe per century and per
10$^{10}$L$^{B}_\odot$ (SNU) as compared to SNIa-rate$(radio-quiet
galaxies)\lsim 0.080 h^2_{50}$ SNU. The exact value of the enhancement is still
rather uncertain, but is likely to be in the range $\sim 4-15$. We discuss the
possible causes of this result and we conclude that that the enhancement of
SNIa explosion rate in radio-loud galaxies has the same common origin as their
being strong radio sources, but that there is no causality link between the two
phenomena. We argue that repeated episodes of interaction and/or mergers of
early type galaxies with dwarf companions are responsible for inducing both
strong radio activity in $\sim$14% of early type galaxies, and the $\sim1$ Gyr
old stellar population needed to supply an adequate number SNIa progenitors.
Within this scenario we predict that the probability of detecting a
core-collapse SN event in radio-loud elliptical galaxies amounts to about 4% of
their SNIa events.
