Leaf curl of peaches
- 1. Leaf curl of Peaches Dr. Chinnamani Prasannakumar PG & Research Department of Biotechnology & Microbiology National College (Autonomous) Tiruchirappalli- 620 001 Tamil Nadu, India
- 2. Background The fungus Taphrina deformans causes peach leaf curl, a plant disease characterised by leaf distortion and colouring. In the United States, Europe, Asia, Africa, Australia, and New Zealand, T. deformans is found. Peach, nectarine, and almond trees are the most commonly affected by peach leaf curl disease.
- 3. Importance The economic impact of the disease varies regionally, as pathogen spread and symptom severity depends on environmental factors. Peach leaf curl costs the United States between $2.5 and $3 million per year. T. deformans can infect anywhere from 60% to 90% of peach shoots in Italy. In dry regions, peach leaf curl is largely treatable with fungicide spraying, although poor timing or incomplete crop coverage can lead to control failure.
- 4. Symptoms Peach leaf curl is an unique and easily detectable fungal disease, and the severity of the symptoms is determined by how early the infection occurs. Because of their crimson colour and twisted shape, diseased leaves can typically be spotted soon after they emerge from the bud. In comparison to typical leaves, the leaves become increasingly deformed as they mature, eventually becoming thick and rubbery. The colour of the leaves shifts from typical green to crimson and purple, eventually covering each leaf in a whitish bloom. Before being discarded, the dead leaf may dry up and turn black. Fruit from infected flowers may not develop. Any fruit that does form on a diseased tree is generally normal, but it might occasionally be affected and turn crimson in colour.
- 5. Cause of peach leaf curl As the infection progresses, the fungus T. deformans creates malformed young leaves, red blisters, and eventually a whitish bloom that covers the leaf. The white colour comes from asci that break through the leaf's cuticle. Eight ascospores make up one ascus, which produce conidia that are expelled in early summer and spread by rain and wind.
- 6. Systematic position Kingdom: Fungi Division: Ascomycota Class: Taphrinomycetes Order: Taphrinales Family: Taphrinaceae Genus: Taphrina Species: T. deformans
- 7. The fungus spends the winter on the host plant's surface, such as bark or buds. Rainwater washes spores into the buds when they burst in late winter or early spring. When this happens, no treatment will work. New leaves sprouting from infected buds are infected by conidia about two weeks after blossoming in the spring. The fungus requires wet winters in which rain (not fog or dew) wets the tree for more than 12.5 hours at temperatures below 16 °C for successful infection. Temperatures below 9 °C are too cold for the fungus to flourish.
- 8. Life cycle About 2 weeks after leaves emerge from buds, leaf symptoms begin. The fungus grows between leaf cells, stimulating them to divide and grow larger than normal, causing the leaf to expand and distort. In the deformed cells, red plant pigments accumulate.
- 9. Fungus cells break through the cuticle of twisted leaves and produce asci, which are elongated sac-like structures that generate sexual spores known as ascospores, giving the leaf a greyish white, powdery or velvetlike look.
- 10. Ascospores are released into the air, where they are transferred to new tissues and bud (divide) into bud-conidia. The fungus survives the hot, dry summer on the tree's surfaces as ascospores and bud-conidia (asexual spores). The ascospores germinate and produce new bud-conidia as the weather turns cool and damp in the fall. By budding, the number of new and old bud-conidia continues to grow. On the tree's surface, a layer of bud-conidia eventually forms. The bud-conidia can infect new leaves by spilling water from irrigation or rain in the spring.
- 11. Molecular mechanism behind infection Taphrina deformans hyphae that develop in intercellular spaces produce polysaccharide-degrading enzymes such cellulase, causing the host cell wall to partially dissolve. Changes in the plasma membrane are also a byproduct of this process. T. deformans converts L-tryptophan to the auxin indole-3-acetic acid via indole-3- pyruvic acid and indole-3-acetaldehyde. The infection's hyperplastic impact is assumed to be caused by this process.
- 12. Control of the disease Deactivating the fungus by keeping winter rain off the buds before they burst (and, coincidentally, delaying blossoming until spring frosts have passed). Spraying fungicides on the leaves is the most popular commercial control approach. Spraying should be done well before budding in the winter. Treatment is useless if trees are not treated early enough. Fungicides such as copper-based compounds (such as Bordeaux mixture) and lime sulphur are often utilised.