On green fruit, root rot will produce distinct brownish-black lesions that have a definite concentric or target-like appearance. In moist conditions, white fluffy fungal growth will develop on infected fruit. Over time, infected fruit will become soft and mushy.
Fungi can enter through openings in the roots, either through natural openings or through wounds. Any enjury to the tomato fruit can provide an entry point for a rot. Fruit spots, insect feeding, cracking, bursting, blossom - end rot are just few examples of conditions that can provide entry points for the fruit rot .