They may require a source of heat at the point where the graft is on the adjoining stems.

It is the latex that comes in the way of success of grafting, it does not allow the plant hormones to form a successful establishment, appears some sort of treatment is required in this regard 

The modified veneer graft, with or without the retention of leaves is among the most successful techniques for grafting the jackfruit. This method requires active scions of 10 to 15 cm with a swollen terminal bud. Other successful techniques include chip budding, cleft and forkert grafts. The key to all of these methods is the vigor of the rootstock and scion, and the preparation of the budwood.

Thank you sir for the input

sorry

i dont know

Youc can try soft wood grafting in jackfruit in a humid condition. I hope the following links may help

http://www.actahort.org/members/showpdf?booknrarnr=890_11

http://www.researchjournal.co.in/upload/assignments/8_409-413.pdf

Thank You