12511
Physiological Disorders
Some environmental and nutritional stresses cause several physiological disorders,
namely, bumpy, carpelloid, lumpy and deformed fruits, vivipary and white seeds.
These are emerging physiological anomalies of developing papaya fruits and seeds
in seed production.
11.1 Bumpy Fruit
Boron has significant influence over production of uniform and healthy fruits, besides
this, it also increases the production of fruits. Bumpy fruit of papaya is associated
with boron deficiency. It occurs in papaya-growing areas of the world. The germ-
plasm line, Pune selection-3 was the most susceptible under Bihar conditions against
this disorder (Table 11.1). It may be due to comparatively higher boron requirement
of this genotype.
11.1.1 Symptoms
First symptoms expressed are moderate chlorosis of mature in ripe leaves, followed
by deformation of leaves, becoming fragile and curved towards back side and bleed-
ing latex on leaves, stem and petioles. Death of apical sprout allows a lateral bloom-
ing. Fruit deformity first starts in young fruits, but symptoms become more severe
on fruits close to physiological ripening (6–9 months at onset of fruit harvest). The
bumpiness begins on the fruit epidermis due to boron deficiency, stopping the fruit
growth. In addition to this, infected tissue continues increasing its size and ends
forming a protuberance or ‘bump’, similar to a ball. Usually, initial symptoms occur
during the formation of young developing fruits, in which latex can be observed
bleeding over fruit epidermis and peduncle with an initial deformation that becomes
evident very slowly (Nishina 1991). Seeds in affected fruits are often aborted or
poorly developed and vascular tissue is mild and almost always with necrosis (Saran
et al. 2013a, b, c, d). Under severe deficiency situations, height of trees may be
affected causing a slight rosette effect and an associated stunting in apical part. In
plants, the first symptoms are an abundant blooming, a latex secretion during fruit
development and a deformation of these fruits later on (Fig u re 11.1). If soil analy-
sis does not indicate boron availability for the plant, for this reason there has to be
considered the deficiency symptoms. Many times, deficiency is confused with the
disease of ‘Bunchy Top’, and for this reason it is suggested to make the test of fruit
chopping and observe latex secretion. Boron deficiency appears more frequently in
shallow, sandy and rocky soils in dry conditions. Trees with deformed fruits typi-
cally have boron levels in petioles (dry weight basis) of about 20 ppm and below
(Wang and Ko 1975). Normal boron levels in petioles are about 25 ppm and higher
(Chan and Raveendranathan 1984).