Question

what are the sources of merchandise in a wholesale market of grains

Answer 1

Wholesale markets for grains obtain their merchandise from the farmers. In the case of manufactured food items, it is directly obtained from the Companies or from distributors of those Companies. In the case of fishes, wholesellers obtain supplies from fishermen or from big merchants in distant places if the specific types are not available from local sources. Supplies of eggs and poultry are obtained directly from hatcheries or poultry farms.
In the case of non-edible consumer durables and non-durables, the wholesellers obtain supplies from Companies manufacturing them or from the appointed distributors of those Companies.