Host-specific adaptation of diverse betasatellites associated with distinct Indian tomato-infecting begomoviruses.

Tomato leaf curl viruses cause major crop loss hindering tomato cultivation worldwide. The 'Old World' begomoviruses are often associated with circular ssDNA satellite molecules called betasatellites. In the present study, replication compatibility of five different betasatellites with three distinct Indian tomato-infecting begomoviruses representing each of a monopartite, a mono-bipartite and a bipartite begomoviruses was studied. All the betasatellites could be trans-replicated by the begomoviruses in Nicotiana benthamiana plants, however, not uniformly in tomato. Tomato leaf curl Joydebpur betasatellite-Magrahat could not induce symptom with any of these begomoviruses in tomato, whereas only Tomato leaf curl Gujarat virus could trans-replicate Radish leaf curl betasatellite in this plant species. However, none of the betasatellites were found to complement the movement function of a bipartite begomovirus in tomato. Unlike tomato, the trans-replication/maintenance of betasatellites by these begomoviruses in N. benthamiana could be due to its compromised host defence machinery. Co-infection of betasatellites with these viruses did not enhance the helper virus accumulation, but the incubation period was reduced. The possible factors involved in this host-driven adaptability of betasatellites were also discussed.