Go to field look for population of a tree species, study the various sttributes,like unbrancehd ,good foliage,early flowering ,,good feproductive biology,bold seeds etc. Take suitable explants if you good storage faciltyin the field(ice tub) colect shoot apices, young leaves etc and folowing the routine protocoal you will be successful,If seeds are there germinate and use various cmopnebts and reneherate as you may please

Select the good parent trees, such as good tree canopy, health foliage, health trunk, productive trees, of course don't contaminate with fungus. 

Dear Ramamurthy

I would be happy to expalin the procedure for selection of candiadate plus tree for tissue culture provided I need to know the objective of your selection.

Because the plus tree selection for timber wood production is diiferent from the selection of plus tree for fruit and other non-Timber Products selection

Kindly go through the attachment which help you to certian extent 

Dear Dr. Hegde 

Thank you very much for your suggestion and I can read this manual

With best regards.