Physiological disorders
Of
physiological disorders, uneven ripening, post-harvest berry drop, flower-bud
and flower drop and pink berry formation are major ones.
Uneven
ripening
Presence
of green berries in a ripe bunch of coloured grapes is called uneven ripening.
It is a varietal character and a problem in Bangalore Blue, Bangalore Purple,
Beauty Seedless and Gulabi grapes. Within a variety this problem varies from
bunch-to-bunch. Generally inadequate leaf area, and non-availability of
reserves to a developing bunch is the reason. Cultural practices like cluster thinning,
girdling and use of growth regulators can reduce uneven ripening. Application
of Ethephon (250ppm) at colourbreak stage is recommended to reduce the problem.
Postharvest
berry drop
This
is due to weak pedicel attachment to the berries. This is common in
Anab-e-Shahi, Cheema Sahebi and Beauty Seedless. Spraying of NAA (50ppm), a
week prior to harvesting can minimize the post-harvest berry drop.
Flower-bud
and flower drop
When
panicles are fully expanded, the flower-buds drop before the fruit set. This is
common in north India but not in the south. The reasons for this disorder are
not known. Stem girdling about 10 days prior to full bloom can reduce the
problem.
Pink
berry formation
It
is a common disorder in Thompson Seedless and its clone Tas-A-Ganesh in
Maharashtra. Pink blush develops on a few ripe berries close to harvesting. The
pink colour turns to dull red colour and the berries become soft and watery.
They do not stand for long after harvesting. Although the definite cause of the
disorder is not known, it is recommended to spray a mixture of 0.2% ascorbic
acid and 0.25% sodium diethyl dithiocarbamate at fortnightly intervals
commencing berry softening.
No comments:
Post a Comment