If the land was registered in the name of Sri.Chikkaravanna then he had an indefeasible legal right to sell it to any one he desired. His children had no right in the land unless the same was ancestral in nature. If the land was sold with proper documentation to T.Saroja then Sri.Chikkaravanna or his children ceased to have any right therein. You must be having in your possession a copy of the sale deed which Sri.Chikkaravanna made in favour of T.Saroja. It can throw light on whether sale was complete or not and also whether requisite stamp duty was paid. If sale in favour of T.Saroja was complete and lawful then she could have as legal owner of the land sold it to you.
Now that his daughters have filed a suit for partition you should contest the same through your lawyer so that you succeed in repelling their legal challenge.