Two different cracking occur on tomato. Radial cracking originates from the stem end and progresses toward the blossom end. Concentric cracking occurs in a ring or rings around the stem scar.
Early signs of fruit cracking can be seen on green or on ripe fruits as small bruises that may expand to form larger radial cracks all around the fruit in this case with numerous cracks.
Cracking occurs when the internal expansion is faster than the expansion of the epidermis and the epidermis splits. Varieties differ greatly in their susceptibility to cracking.
Cracking can occur at at all stages of fruit growth but as fruit matures they become more susceptible. The more resistant a variety is, the later in maturity of the fruit cracking may occur.