I got 17 marks in BL paper, all India rank 2623 in jam 2019, and my category ST , can I apply for the further admission process in iisc ?

Hello Dhananjay. Congragulations for qualifying in JAM. IISc provide I.PhD which can be accessed through IIT JAM. As you qualified in BL paper, you are eligible to apply for admission in IISc. In order to apply to IISc through JAM you have to apply via the admission portal of IISc Admissions. But the deadline was 25th of March 2019.

If you have already registered then you can check for the probability for getting admission in IISc via cut-off of previous year.

Please visit https://www.iisc.ac.in/admissions/cut-off-report-and-gate-score-of-previous-years/

There are opening and closing All India Ranks (AIRs) which will be published for getting admission. But for ST category that lies in range 450-750 and varies every year depending on the qualifying marks and the number of individuals who are there in the list.