Tomatoes - Crop Post-Harvest: Science and Technology - page 17

Bacillus and Pseudomonas . Infection is almost exclusively
via wounds or other openings in the fruit, and is especially
likely if fruit come in contact with contaminated water.
Symptoms include soft and water-soaked areas that become
liquefied, and bacterial ooze may leak from wounds,
stem scars and stylar pores (Plate 2.12a-c). Control is by
sanitation to reduce population levels, avoiding excessive
submersion in dump tanks and flumes, avoiding damage to
fruit and culling fruit with cuts, punctures, abrasions and
large scars that can provide entry to the pathogen.

include adequate ventilation and reduced humidity in the
greenhouse. Tomato cultivars vary in their susceptibility.

Bacterial speck
This is caused by Pseudomonas syringae pv. tomato. The
symptoms are in the form of dark, minute (less than 1 mm)
lesions, and the skin may appear tough. Preventive
measures include seed treatment with hot water or with
chemicals and greenhouse sanitation.

Phomopsis rot
Caused by Diaporthe phaseolarum var. sojae , the disease
takes the form of soft and water-soaked lesions. The
infected tissue may turn tough, dark and shrivelled.
Greenhouse sanitation and careful handling are among the
preventive measures.

Sour rot
This is caused by Geotrichum candidum . Symptoms on
mature-green fruit appear as pale lesions, dull and water
soaked, with sour (vinegar) odour (Plate 2.13). On ripe
fruit the infected tissue is usually dark, soft and watery.
Symptoms usually start at the stem scar and resulting from
wounding. Avoiding mechanical injury is an important
preventive measure.

Pink mould rot
Caused by Trichothecium roseum Link, it is characterised
by firm greyish-brown lesions at the blossom end of the
fruit. Lesions are usually water-soaked and in humid
conditions give rise to characteristic orange-pink spores.
Preventive measures include adequate ventilation in the
greenhouse, avoidance of injuring the fruit and the use of
adequate storage temperatures.

Hairy or Rhizopus rot
This is caused by Rhizopus stolonifer and characterised by
soft, water-soaked and discoloured lesions with fermented
odour (Plate 2.14). A coarse white mould may appear
which then turns black (Plate 2.15). Preventive measures
include adequate hygiene in the greenhouse and on the
packing line, and avoidance of fruit injury. The fungus
grows very slowly at around 10°C and lower.

Pleospora rot
Caused by Pleospora herbarum , this disease is character-
ised by brown to black lesions at the edge of the stem scar
or on wounds at any part of the fruit. Preventive measures
include careful handling.

Phoma rot
Caused by Phoma destructera , this disease is characterised
by firm, sunken lesions that occur commonly at the stem
end, but can also occur at any part of the fruit. The infected
tissue appears brown in colour and then turns black.
Preventive measures include eliminating diseased plants,
avoiding fruit injury, using optimum temperature during
storage and shipping and ensuring hygienic practices.

Ring rot
Caused by Myrothecium roridum , it is characterised by
circular to oval, firm and slightly sunken lesions, with
sharply defined margins. This decay extends deep into the
fruit. Preventive measures include pre-planting treatment
of seeds, hygiene in the greenhouse and packinghouse and
the avoidance of mechanical injury.

Early blight rot
This is caused by Alternaria solani . The symptoms are in
the form of dark-brown lesions that commonly appear at
the stem end, but may also appear at the blossom end or
at the side of the fruit. Lesions are sunken and leathery in
green fruit. Preventive measures include the chemical
treatment of seeds before planting.

FUTURE CHALLENGES OR DEVELOPMENTS
New post-harvest technologies are poised to change the
ways by which tomatoes are handled. Near-infrared and
acoustic online sorting devices can be used to determine
internal quality aspects related to maturity and ripeness
such as sugar content and acidity, dry matter, juice
content, internal structure as well as internal physical
defects. The ability to sort out immature and defective
tomatoes on the packing line can lead to improved tomato
quality at the same time that handling efficiency is
enhanced. Radiofrequency identification (RFID)-enabled

Late blight rot
This is caused by Phytophthora infestans . This problem
can affect protected or outdoor tomatoes. Hard, lumpy,
reddish-brown lesions can appear in different parts of the
fruit, but commonly at the stem end. Preventive measures