Agriculture Reference
In-Depth Information
Spongy tissue
Spongy tissue is a disorder specific to 'Alphonso' mango,
and the term has been interchangeably used with internal
breakdown (Krishnamurthy 1981; Subramanayam et al .
1971). Spongy tissue is characterised by the yellowish
white corky patches with or without air pockets in the
mesocarp tissue and is observed at or after the onset of
ripening. Spongy tissue disorder is under genetic control
and restricted to only a few cultivars. 'Alphonso' mango
in India suffers from this order to the extent of 35% to
55% (Vasanthaiah et al . 2006). Numerous factors have
been associated with the incidence and severity of this
disorder such as pre-harvest heating of fruit in the field
due to convection, post-harvest heating during handling
and storage, low calcium content, nutrient imbalances,
late harvesting, low fruit transpiration, large fruit size,
internal O 2 and CO 2 concentrations in response to CA or
MAP and oxidative stress (Katrodia et al . 1989; Katrodia
& Sheth 1989; Krishnamurthy 1981; Leon et al . 2000;
Lima et al . 2000; Shivashankara & Mathai 1999;
Vasanthaiah et al . 2006). But there is no consensus among
researchers about the actual cause. The affected pulp
tissue contains high starch content and total pectin, low
soluble pectin, low reducing and nonreducing sugars, low
b -carotene, low Ca and K, higher P, low pH and low
ascorbic acid contents. The biochemical and metabolic
disturbances in the affected tissue result in increased
or decreased activities of certain enzymes associated with
the development of symptoms. The reduced activities of
α-amylase, invertase, polygalacturonase and pectin
methylesterase are associated with the high starch and
low-soluble pectin contents in the spongy tissue (Katrodia
et al . 1989; Lima et al . 2001). The activities of certain
enzymes such as peroxidase, polyphenoloxidase (PPO)
and phenylalanine ammonia-lyase (PAL) are triggered in
the disordered tissue (Lima et al . 1999).
Harvesting of mangoes before full maturity can reduce
the spongy tissue and seems to be the most economical and
adoptable strategy (Subramanayam et al . 1971). High
humidity prevailing inside the tree canopy or in the
atmosphere causes poor uptake of nutrients due to lower
transpiration pull; it ultimately leads to higher incidence of
spongy tissue (Shivashankara & Mathai 1999). The proper
training and pruning practices, sod culture (Katrodia &
Sheth 1989) and pre-harvest and post-harvest application
of Ca (Gunjate et al . 1979; Hermoso et al . 1997;
Krishnamurthy 1981) have been reported to ameliorate the
symptoms of spongy tissue. The long term storage of fruit
in an optimum CA or MAP should be practised to control
this malady. The possible measures to mitigate post-harvest
oxidative stress in the fruit need further investigations. The
detection of spongy tissue in the fruit with X-ray imaging
can be used for elimination of affected fruits on the pack-
ing line (Thomas et al . 1993).
There is also confusion between soft nose, jelly seed and
stem-end cavity (SEC) disorders which are completely
different from each other (Raymond et al . 1998). The
observations of flesh breakdown symptoms at an advanced
stage of mature or ripe fruit make it difficult to differentiate
among different disorders. Raymond et al . (1998) described
the symptomology of jelly seed, soft nose and SEC and
classified them as separate disorders under the common
terminology of IB.
Soft nose can be described as the breakdown of flesh at
the distal end of the fruit (Young 1957). This causes the
premature softening of the mesocarp at the distal end of
the fruit with little external sign of the developing disorder.
Raymond et al . (1998) defined it as an incomplete ripen-
ing of the mesocarp tissue at the distal end of the fruit,
which in early stages results in a defined yellow area
between the apex of the stone and the exocarp. The non-
uniform distribution of calcium in the fruit has been
observed as the causal factor for soft nose. The Ca concen-
tration in the stem end portion of the fruit is high and
decreased to the least at the distal end (Burdon et al .
1991). After tissue breakdown, Ca redistribution results in
high Ca concentration in affected tissue. The accumula-
tion of calcium in the disordered tissue may assist in the
spread of the breakdown by depleting the mineral content
of the adjacent mesocarp (Burdon et al . 1991). Cultivar
plays a considerable role in the development of this
disorder as some Indian cultivars are more susceptible
(Young 1957).
Jelly seed is localised all around the endocarp result-
ing in the intense yellow colour of the inner mesocarp
which eventually becomes brown and softens to the con-
sistency of jelly, so called jelly seed (Raymond et al .
1998).
Stem-end cavity (SEC) is characterized by the formation
of a cavity in the proximal area of the fruit resulting from
the deterioration of the vascular tissues between the proxi-
mal end of the stone and the fruit peduncle (Raymond et al .
1998). However, there is no cavity, air pocket, gap or tissue
necrosis developed in fruit affected with jelly seed and soft
nose. Jelly seed and SEC are observed first after 8 weeks of
fruit set whereas soft nose symptoms are only observed in
fully mature fruit (Raymond et al . 1998). These disorders
are either under genetic control or mainly caused by the
nutrient imbalances. The causes of these disorders warrant
further investigations.
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