Tomato fruit bronzing

SUMMARY Tomato fruit bronzing occurs in green fruits and produces variable symptoms in ripe fruits. The bronzing is caused by brown necrosis of the fruit wall, mainly at the calyx end of the fruit, which is also the most severely affected part. Field observations and experiments showed that bronzing is closely associated with infection of the plant with tobacco mosaic virus (TMV) and some other factors, notably rank or ‘soft’ growth. Symptoms occur within a short time of infection with TMV and affected fruits are produced over a relatively short period on any one plant. The symptoms in a particular fruit remain constant and do not get progressively worse. Plants systemically infected with TMV do not subsequently produce bronzed fruits. This disease can be distinguished from some other tomato fruit disorders such as blotchy ripening and appears to be similar to a disorder in the U.S.A. called internal browning. A second type of bronzing in green fruits is less common but symptoms are more severe. In this case the necrosis of the fruit wall is not particularly associated with the calyx end and it gets progressively worse so that the fruit is often unsaleable; a characteristic symptom is a series of dark lines radiating from the stylar end of the fruit. Affected fruits are produced on a particular plant over a long period of time and are not associated with infection of plants with TMV. A histological examination of both types of bronzing is reported.