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POSTHARVEST DISEASES OF CHERRY AND THEIR MANAGEMENT


By Syed Adeel Sajid1 and Bilal Akram2

(1Department of Plant Pathology, 2Department of Horticulture, College of Agriculture, University of Sargodha)

Cherry fruit is a fleshy drupe containing a stone in
the center surrounded by a fleshy part. Nutrient rich fruit with comparatively
low caloric content. It also comprises of substantial amounts of important
nutrients including fiber, polyphenols, carotenoids,
vitamin C, and potassium. Cherries
are also good source of tryptophan, serotonin, and melatonin. There are two major categories: tart and sweet cherries, or Prunus cerasus L.
and Prunus avium L., respectively. Their colors can vary from yellow to deep blackish-red. Fruit of hilly areas needs low temperature and several
chilling hours for quality fruit. In
Pakistan, cherries are cultivated in the Northern areas, Gilgit-Baltistan and
Baluchistan. According to FAO (STAT.), production of cherry in
Pakistan was 2206 tons in 2017. Cherries are used for
frozen pies and pie filling and for canning, bakeries, ice cream, sauces,
preserves and other deserts.

Health Benefits:

Cherries are a rich source of polyphenols and vitamin
C which have antioxidant and anti-inflammatory properties and great for healthy skin, strong tendons, ligaments, blood vessels
and cartilage. These delicious
fruits also provide a small amount of zinc, iron, potassium, manganese and a magnanimous helping of copper. Potassium helps regulate heart rate and
blood pressure.  The boron in
cherries helps increase bone health as part of a magnesium and calcium enriched
diet.

Postharvest losses and decay:

Postharvest diseases develop on fruit
and other plant products after harvesting during grading, packing, during
transit, transportation to market and consumer and while the produce is in the
possession of the consumer until the moment of actual consumption. The plant products may show the symptoms
of the diseases that began in the field but remained latent. The pathogenic
organisms secrete toxic substances that make the product or its part unfit for
consumption. Pathogens causing postharvest diseases attack healthy and living
tissue which they disintegrate and cause to rot.

Cherries are highly perishable and demand care to handle after harvest. In developing countries, postharvest
losses are often more severe due to inadequate storage and transportation
facilities. In Pakistan, almost 20 to 30% of cherry is lost due to postharvest
management and diseases. The main postharvest pathogens are of fungal origin
like molds. The fungal inoculum
arrives into the pack-house with the hard vdvested
fruit, on its surface, in disease fruits, on contaminated tools and bins and
with orchard litter. Cracks
in cherries act like wounds due to mishandling, insects, rodents and farm tools act as entry points for fungal spores to enter the fruit and proceed to decay the fruit. The extent and nature of damage
depends on the picking conditions, handling, type of product, disease organism
and storage conditions.

Environmental conditions of produce play
an important role in development of infection by the pathogens following
postharvest wastage of the produce. Factors like temperature, moisture,
composition of CO2 and O2 seriously affect the initiation
of infection and development of symptoms. Storage temperature is so critical
for controlling postharvest diseases. High temperature and humidity favour the
development of postharvest decay in cherries. Ripe fruits are more susceptible
to invasion of pathogens and some pathogenic fungi most likely to invade after
the fruit is completely ripe or has become senescent.

Postharvest pathogens of cheery
include Penicillium spp., Botrytis cinerea, Monilinia spp.,
Cladosporium spp., Rhizopus stolonifer, Alternaria
spp. and bacteria such as Erwinia and Pseudomonas.

Major Postharvest Diseases of Cherry

  1. Alternaria Fruit Rot:

Alternaria fruit rot also known as
sooty mold and dark spot disease caused by Alternaria alternata. Infection
starts when fungus takes entry through wounds and producing dark brown circular
spots. Later on, as the disease proceeds, the spots coalesce to form lesions
containing concentric circles of spores. Fruits become wrinkled with dark
lesions.  A. alternata has
been regarded as the major mycotoxin-producing specie in Alternaria spp..

 
Gray mold is a devastating disease of fruit during postharvest caused by
Botrytis cinerea. This pathogen may produce disease symptoms in the
pre-harvest period or remain quiescent until post-harvest period. The annual
economic losses of B. cinerea easily exceed $10 billion worldwide.
It has both asexual stage (conidia) and sexual stages (sclerotia) to survive in
favorable or unfavorable conditions. Infected fruits turn gray-white, soft and
rot. A mass of grey-brown
conidia produces on brown lesions.

This mold of cherry is caused by
Cladosporium herbarum
so also known as Cladosporium Rot. Spores of
this fungus enter the fruit through
breaks in the skin, and proceed to decay the fruit. Fruit tissues become hard, decayed
with grey to black discoloration.

Brown rot is caused by the ascomycete fungus Monilinia fructicola and is an
important pathogen on cherry. The
pathogen can infect fruits directly without the need for wound. The
fungus attacks fruit as well as
other plant parts. In ideal environmental
conditions, due to its fast-reproductive
cycle pathogen initiate epidemic inoculum levels in as little as 24 hours. In start, dark spots develop on fruits and
later on coalesce with each other. Fruit wrinkles and covers with brown
conidial sporulation (mummy) and mostly fall onto the ground. Fungus overwinters in the mummified fruits, which serve as sources of inoculum for
the coming season.  

This disease is also known as watery white rot because
fruit tissues become watery and a profuse production of coarse white fungal strands with black spore
heads (sporangia). Rhizopus
rot which is one of the most severe postharvest diseases of cherry caused by Rhizopus
stolonifer
a typical postharvest pathogen. Rhizopus rot enlarge rapidly and
can involve the entire fruit in 24 to 48 hours.

Blue mold is caused by an important postharvest pathogen Penicillium
expansum
. The fungus
is characterized by the blue-green velvety sporulation covered by white expanding mycelium therefore called as blue
mold. At early infection
stages, blue mold symptoms include light tan to dark brown circular lesions
with very sharp margin between diseased and healthy tissues. Decayed fruit has an earthy, musty odor. The fungus can grow at temperatures as low as -3ºC (27ºF) and germination can occur at
0ºC (32ºF).

     
Management:

 All diseases either postharvest or pre harvest
diseases can be controlled by proper              handling and good agricultural
practices which involves cultural practices and timely and perfectly harvest to
counter postharvest diseases.

  1. Cultural Practices
  2. Careful
    handling, removal of damaged fruit, and rapid cooling are effective methods of
    decay management for these diseases.
  3. Wounding
    to the produce can be minimized by careful harvesting, sorting, packaging and
    transportation, including preventing the fruit from falling at all stages.
  4. Eradicate crop debris that may
    serve as sources of inoculum.
  5. Hydro-cool
    cherries as soon as possible after harvest.
  6. Physical Practices
  7. These
    diseases may be controlled by various physical treatments, such as, low
    temperature storage, high temperature treatments, magnetic fields and radiation.
  8. Hot water
    treatment of 52ºC for 2 minutes is effective for controlling cherry rots.
  9. Hot air treatment at
    44°C for 114
    minutes is effective in
    inducing disease resistance and suppressing blue mold decay in cherries.
  10. Preharvest treatment of cherry fruits with 2mM salicylic acid and 0.2mM
    methyl jasmonate is significantly effective to reduce brown rot.
  11. Preharvest
    application of iprodione at 1.13 kg a.i./ha with a postharvest dip in a
    suspension of C. infirmo-miniatus containing 0.5 to 1.5 × 108 CFU/ml. is
    effective for control of brown rot.
  12. Chemical Treatments
  13. Dicloran
    and Iprodione are effective against Rhizopus spp.
  14. Imazalil
    is good for managing Alternaria rot.
  15. Thiabendazole
    & Carbendazim are effective against Brown rot, Blue mold and Gray mold.
  16. Benomyl,
    Thiophanate-methyl, Captan, Chlorothalonil + Sulfur, DCNA, Sulphur are also
    effective as chemical treatments for Brown rot.
  17. Biological Control
  18. A
    bacterial strain Bacillus subtilis by producing antibiotics
    significantly control Brown rot and Gray mold of cherry.
  19. Enterobacter
    aerogenes
    is effective against
    Alternaria rot.
  20. Antagonistic
    yeasts, Trichosporon pullulans, Cryptococcus laurentii, Rhodotorula glutinis,
    and Pichia membranefaciens are effective against several of the main
    postharvest pathogens on sweet cherries at 25◦C.



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