Agriculture Reference
In-Depth Information
15
PA SSIONFRUIT
(
Passiflora
spp.)
P a s s i of n f r u i t w a s t h e n a m e g i v e n t of s p e c i e s of f t h e g e n u s
Passif lora
by early Spanish missionaries in South America
who saw the story of the crucifixion in the f flower
structure. The corona represents the crown of thorns; the
five anthers represent the five wounds; the three stigmas
represent the nails on the cross; the five petals and five
sepals represent the ten apostles (excluding Judas and
Peter); the tendrils represent the whips and cords and the
leaf represents the spear.
The genus
Passiflora
has some 400 species, all but about
5% of which originated in the New World. Only two
species are cultivated by industry -
P. edulis
and
P.
quadrangularis. Passiflora edulis
, which originated in
Brazil, has two recognised forms: the purple f.
edulis
,
which is better suited to cooler subtropical conditions,
and the more tropical yellow f.
flavicarpa. Passiflora
quadrangularis
, known as the giant granadilla, is a native
of tropical South America and grows best in hot, moist
climates. Hybrids between f.
edulis
and f.
flavicarpa
were
developed for the Australian industry.
Diseases have a serious impact on production as well as on
the economic life of a passionfruit plantation. Most
plantations have to be replaced after two years due to the
effect of viruses.
Fig 15.1 Symptoms of alternata spot on passionfruit. Note the greasy,
water-soaked margins.
FUNGI
Fig 15.2 Alternata spot developing on fruit damaged by passionvine
bug.
ALTERNATA SPOT
■
Small spots develop on fruit and have a tan or brown
centre with a greasy, water-soaked margin. The spots are
skin deep, not sunken and usually less than 1 cm wide. In
highly susceptible varieties, spots may be up to 3 cm in
diameter. A tear-stain effect occasionally develops down
the side of the fruit.
Cause
The fungus
Alternaria alternata
.
Symptoms
On young leaves, small, necrotic spots occur, surrounded
by yellow haloes up to 6 mm wide with diffuse margins.
On older leaves, dead tissue is surrounded by a yellow or
light orange halo. Leaves may fall after developing only a
few spots. Small stem lesions rarely kill sections of vine.
Source of infection and spread
Spores are produced on infected leaves and fruit and on the
dead blossom attached to the fruit stalk. These are readily
