RATOON STUNTING DISEASE OF SUGARCANE

RATOON STUNTING DISEASE OF SUGARCANE

Causal Organism: Leifsonia xyli Subsp. xyli

Old- Clavibacter xyli

Vivek Kumar

Student [ B.Sc (H) Agriculture ]

School of Agriculture, GEHU (Dehradun)

 INTRODUCTION:

• The disease is present throughout the sugarcane growing areas of our country. CO 419 variety was worst affected in parts of Karnataka where it was withdrawn from cultivation. The disease appears in both plant and ratoon crop, but more pronounced in ratoon crop.

CLASSIFICATION:

• Domain: Bacteria
• Phylum: Actinobacteria 
• Class: Actinobacteria
• Subclass: Actinobacteridae
• Order: Actinomycetales
• Suborder: Micrococcineae
• Family: Microbacteriaceae
• Genus: Leifsonia 
• Species: Leifsonia xyli  Subsp. xyli

SYMPTOMS:

• Diseased clumps usually display stunted growth, reduced tillering, thin stalks with shortened internodes and yellowish foliage (mild chlorosis).
• When mature canes are split open, vascular bundles appear discoloured.
• In young canes, pink colour is seen in the form of minute pin head like areas near the nodes.
• The disease reduces the length, girth and the number of canes per clump.

           Stunted growth                     

Orange pin head dots on internode

        

ETIOLOGY:

• It infect the xylem (water transport) vessels of the sugarcane plant.
• The bacterium is rod shaped, typically with a slight bend and measures 0.25-0.5 μm by 1-4 μm.
• The organism that causes RSD is, Leifsonia xyli subsp. xyli, a small aerobic and Gram Positive bacterium.
• The genus of the pathogen was previously called Clavibacter.

Leifsonia xyli

Microscopic view

SURVIVAL AND SPREAD :

• The two primary methods of spread of the disease are by planting infected cuttings and by use of contaminated cutting implements.
• The bacterium is highly contagious and can be spread for many metres down a row after a planter or harvester cuts a diseased stalk or plant.
• The recirculating fungicide spray system on planting machines can carry the bacteria and spread the disease.

FAVOURABLE CONDITIONS:

• Infected setts.
• Dense planting.

DISEASE CYCLE:

• The disease spreads through use of diseased setts.
• The disease also spreads through cane harvesting implements contaminated with the juice of the diseased canes.
• Maize, sorghum, Sudan grass and Cynodon are some of the collateral hosts of the pathogen.

DISEASE MANAGEMENT:

Cultural method:

• Select healthy setts for planting.
• Field should maintain at proper sanitation.
• Ungerminated setts should be removed and fill the gap with new setts which should be treated before planting.

Mechanical method:

• Treat the setts with hot water at 50°C for about 2 hours this gives 100 per cent control. A temperature higher than this would kill the cane and lower temperature than the specified enables the pathogen to survive.
•   Aerated steam therapy eliminates the pathogen from the infected canes. Use of disinfectants to clean seed cutting tools which would reduce the chance of spread of pathogen from the infected to healthy setts.

Chemical method:

• Chemical disinfectants that may be used on cane cutting knives includes, Lysol, Dettol, ethanol, Mirrol and Roccal. Atleast 5 minutes of contact with the cutting surface is needed to assure disinfection.

Thank You !!

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