Bankok,customs/ag dept have taken many seeds that people have sent me and they have a nose for which are the good ones.Decades ago the state govt and tropical fruit societies were very active here and had trips all over the world getting the best varieties of each fruit type.With jacks, seeds from India,Thailand,Malaysia and Indonesia were brought to Queensland and the best were crossed with each other and selected to improve them.A few good named and are among the common named varieties that are even in places like Florida.It all fell apart,collections got abandoned,govt funding dried up,the fruit clubs disbanded, and cyclones struck.Speaking to the govt researchers of the time amber jackfruit and one called Berry were considered the best by the jackfruit folk.Interestly amber was reduced to a single tree that was 'rediscovered' and Berry is even more scarce being reduced to a single identifiable tree also.
There is probably just as much value in finding the good ones here as getting seeds of overseas good ones.