Production Practices and Quality Assessment of Food Crops. Vol. 1

22 R. M. Madakadze and J. Kwaramba
tration went below 200 mg L –1 blossom end rot was more likely to occur. Longer
NH 4-N supply increased the amount of fruit with blossom end rot in the winter
but had no effect in spring, however, higher NH 4-N concentration in solution in
spring greatly increased the number of fruits with blossom end rot (Sandoval-Villa
et al., 2001).
Sandy soils are also vulnerable to lack of water and nutrients due to high leaching.
Some literature has suggested close spacing in the field and dry winds as encouraging
blossom end rot. Factors that influence the uptake of water and Ca 2+ by the
plant definitely promote development of the disorder. This disorder is most
prevalent when rapidly growing plants bearing fruits are suddenly exposed to a
drought period and when roots fail to obtain nutrients and water due to any form
of damage or otherwise. Factors that encourage rapid growth are high nitrogenous
fertilizer application or high temperatures (Tabatabaei et al., 2001) and light
intensity. Cultivation or hoeing too close to the plant destroys roots interfering
with transportation of water and Ca 2+ predisposes the developing fruit to blossom
end rot. These factors favour development of the disorder. When tomato fruits
were grown with or without infrared light reflective filters to control temperature,
fruits in the unfiltered compartment were 16% larger than those in the filtered
compartment, but Ca 2+ concentration was 12% less. Thirty five percent of fruits
in the unfiltered compartment had blossom end rot compared to none in the filtered
compartment. High temperature reduced Ca 2+ accumulation, but increased K + concentration
in fruits. To control blossom end rot, rapid growth caused by high
temperature should be avoided (Tabatabaei et al., 2001).
4.1.6. Hollowness (Puffiness)
The fruits are light and soft. Fruits appear slab-sided or angular from the exterior.
Various climatic conditions, varietal and nutritional factors cause the malformation.
The cavities of a normal fruit are filled with a jelly-like substance which carries
the seed between the walls and the core. When hollowness occurs the cavities are
not completely filled with the jelly and consequently the fruit becomes puffy or
hollow, light in weight, soft and of reduced quality. Cultivars with two or three
seed cavities are usually more subject to hollowness. High nitrogen applications
in the early stages of growth and incorrect irrigation scheduling facilitate development
of hollowness. It is encouraged in plants that set fruits in cool weather
although bad or inadequate pollination, fertilization and seed development may
contribute to the disorder. These can be due to improper nutrition. Low potassium
nutrition, high nitrogen, high phosphorous coupled with low light and low dry matter
content of the fruit all encourage development of puffiness. The use of auxin growth
regulators for fruit set can also lead to puffiness.
4.1.7. Uneven colouring (blotchy ripening)
This disorder is caused by different factors which include insufficient light, virus
infection and potash deficiency. Too high or too low temperatures during fruit
ripening will cause green or yellow shoulders on ripe tomatoes. Generally high