Tomato Genetics and Breeding Program       

Color Disorders

Internal White tissue, yellow eye, yellow shoulder, and green shoulder appear to represent a range of symptom severity for a single problem, Yellow Shoulder Disorder (YSD).  The disorder, YSD, is characterized by a discolored yellow or green sectors under the fruit peel. The discoloration (ranging from a few millimeters to the top 1/3 of the fruit) is caused by a failure of green chloroplasts in tissue affected by YSD to develop into red chromoplasts. This modification is accompanied by a more random cell orientation and smaller cells relative to mature green fruit.  These changes begin early in fruit development and cannot be reversed by delaying harvest. Understanding that YSD involves altered fruit development rather than delayed fruit ripening is important to management strategies: the problem must be treated before it is seen in the field.

What causes YSD?
The causes of YSD are not yet understood but it is known that factors like soil nutrient status (mainly K, Mg and Ca), weather (temperature, light intensity and rain) and genetics (variety) have some implication on the occurrence of the disorder.

To know more about important soil nutrient variables that affect color disorders click here.

Why is YSD a problem?
YSD affects both the appearance and nutritional value of tomatoes.
Fruits may not show external discoloration but can still have the disorder.
Standards for grading processed vegetables set very strict limitations on the amount of discolored tissue allowed in peeled tomato products. However, grading practices rarely detect internal disorders before peeling. Thus premium prices may be paid for tomatoes that do not yield an acceptable amount of high grade fruit. Processing efficiency is also reduced because the tomato peel adheres to the discolored flesh after peeling; extra labor is then required to sort and divert tomatoes into products that have a lower return. Ultimately, both the growers and processors would be negatively affected by YSD. 

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