Post harvest lecture citrus-1
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This presentation is a mere compilation of citrus post harvest diseases solely for education purpose. Most of the photographs and literature is from the post harvest book "Post harvest diseases and disorders of fruits and vegetables, Vol.I" authored by Anna L. Snowdon. The presentation is intended for PG students of plant pathology.
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Post harvest lecture citrus-1
- 1. Post harvest diseases of citrus Dr. P. Kishore Varma Assistant professor PJTSAU, Hyderabad
- 2. Green and blue mold – Penicillium spp. Green mold • Penicillium digitatum (green mould) • P. italicum (blue mould) • Softening of damaged tissue. • White fungal growth, which progressively turns blue or green as spores develop.
- 3. • Infections develop from damaged areas. • The growth of mould increases with storage • Optimum temperatures (20-270 C). • Late season fruit more susceptible. • Damaged rind is more susceptible. 3 Blue mold Green and blue mold – Penicillium spp.
- 4. Pathogen biology – Penicillium digitatum Penicillium digitatum Penicillium italicum
- 5. Sour rot - Geotrichum candidum / G. citri-aurantii • Very soft, watery decay. • Distinct margin between decayed and healthy tissue. • Lesions covered with slimy off-white spores • Sour odour detectable.
- 6. • Prevalent after warm wet areas • Pathogenic on ‘weak’, wounded, bruised, and split fruit • Lemons, limes and grape fruits stored for extended periods • Ripe fruit is more susceptible 6
- 8. 8 Stem end rot - Lasiodiplodia theobromae • Softening of tissue around button • Brown rind with dark flesh beneath • Rapid decay down the axis of the fruit reaching stylar end
- 9. • Abundant rainfall during crops eason • Ethylene degreening treatments predispose fruit to Botryodiplodia infection • Quiesecent in floral remnants under the sepals of fruit • Botryodiplodia – 300 C • Phomopsis, Dothiorella - 230 C 9
- 11. Phomopsis citri
- 12. Dothiorella
- 13. 13 Brown rot - Phytophthora citrophthora • Greyish brown firm and leathery spot • Pungent odour • Fine white spore bearing mould on peel • Develops rapidly at - 250 C
- 14. Phytophthora citrophthora, P. citricola, P. hibernalis 14
- 15. Anthracnose - Colletotrichum gloeosporioides Tear stain • Superficial leathery appearance • Silver/grey to dark lesions. • Tear-staining pattern • Pink tinge (spores) under humid conditions.
- 16. • Infection occurs by rain-splash during autumn. • ethylene degreening increases sensitivity to anthracnose • Quiescent - appressoria 16
- 18. Trichoderma rot - Trichoderma viride • Peel turns dark brown • Veins on the interior surface of the peel turn brown • Odour of coconuts • Yellow green to dark green sporulation on surface
- 20. Management • Careful handling • Sanitation • Sodium-ortho phenyl phenate, sodium carbonate • Benzimidazole and imazalil • Curing citrus fruits at 360 C for 3 days • Yeast, eg. Debaryomyces, Pichia • Candida famata, Pseudomonas syringae, Aureobasidium pullulans • Aspire – Candida oleophila • Biosave – P. syringae 20
- 21. Management • Stem end rots – TBZ, Benomyl, Imazalil, prochloraz • Brown rot – Fixed copper fungicides, Metalaxyl, Fosetyl-Al • Hot water dip treatments at 46-490 C for 3 min • Stem-end rots – Refrigeration between 4-70 C • Anthracnose- <100 C 21
- 22. Citrus disorders Chilling injury • Critical temperature – 10-150 C for grapefruit, lemons and lime • 1 and 50 C – Oranges, mandarins • Brown pitting of rind • Watery breakdown • Brown staining of peel or peel tissue collapse • Oil gland darkening – grapefruits • Albedo browning, membranous stain - lemons 22
- 23. 23
- 24. Chilling injury • Abnormal biochemical changes • Moisture loss from peel • Growth regulators and fungicides • Varies from season to season Chilling injury vs. Pitting 24 Peel tissue collapse Develops in 4-6 weeks in storage Reduced by waxing Oil gland targeted Develops in 3-4 days Caused by wax application
- 25. Chilling injury-Management • Reduction of moisture loss by applying oil, wax (shellac) or film • Maintain high humidity • Sealing in polyethylene film • Pre-conditioning of fruits to chilling temperatures • Intermittent heating • Fungicide application (eg. TBZ) • Low oxygen and high CO2 25 Optimal temperature with proper wax is the best means for controlling chilling injury
- 26. Freezing injury • Temperature below -1.50 C • Browning of peel • Water soaked membranes between the segments • Mandarins- crystals in pulp • Grapefruit – milky appearance of pulp • Cavities in flesh 26
- 27. 27
- 28. Oleocellosis or rind-oil spotting • Common on lemons and limes • Injured areas firm, irregular in shape • Yellow, green or brown discolouration • Oil glands appear prominent Reasons • Compression of fruits • Sudden spell of cold weather • Physical injury to the peel • Fruits harvested in cool, wet periods 28
- 29. Oleocellosis Management • Pre-harvest spray of ethylene • Avoid harvesting immature turgid fruits • Avoid picking too early in the season 29
- 30. Other disorders 30 Creasing Chemical injury Peteca Puffiness