Caste related information is a third party information under section 8(1)(j) of the RTI act. As per section 8(1)(j) of the RTI Act, 2005 the income tax returns, movable and immovable property, details of investment, salary, show causes or punishment issues of an employee, caste details etc are exempted from disclosure, unless a larger public interest is involved.
You have to either show that you are related to this person or show that there is some public interest involved in this information.
However, you can ask the total number of employees in various categories in the different departments Karnataka Government. You have to file separate RTIs to separate Govt offices.