GRASSY SHOOT DISEASE OF SUGARCANE

  GRASSY SHOOT DISEASE OF SUGARCANE

        Causal Organism: Candidatus sacchari

 Juhee Kumari

Student [B.Sc(H) Agriculture]

School of Agriculture, GEHU (Dehradun)

INTRODUCTION:

•  The grassy shoot disease (GSD) of sugarcane occurs in most of the Asian countries, affecting sugarcane production to a considerable level.
•  It was first noticed in India in 1919 in Maharashtra. 
•  The disease is caused by grassy shoot phytoplasmas. In India the disease occurs in all the sugarcane growing states.       

CLASSIFICATION:

•  Domain: Bacteria
•  Phylum: Firmicutes
•  Class: Mollicutes
•  Order: Acholeplasmatales
•  Family: Acholeplasmataceae
•  Genus: Candidatus
•  Species: sacchari   

     

SYMPTOMS:

•  Initial symptom appears in the young crop of 3 – 4 months age as thin papery white young leaves at the top of the cane.
•  Later, white or yellow tillers appear in large number below these leaves (profuse tillering).
•  The cane becomes stunted with reduced internodal length with axillary bud sprouting.
•  This disease appears in isolated clumps.   

Whitining of leaf

Profuse tillering

            Reduced internodal length  

             

Grassy shoot

             

ETIOLOGY:

•  Phytoplasmas, formely called Mycoplasma like organisms (MLOs).
•  Its large group of obligate, intracellular, wall less, Shape less.
•  It is Gram positive Bacteria.
•  Its found in the Phloem cells of infected plant.
•  Two types of bodies are noticed , spherical bodies of 300-400 nm diameter and filamentous bodies of 30-53 mm diameter in size.   

SURVIVAL AND SPREAD :

•  The grassy shoot disease is primarily transmitted through the diseased seed material (setts) and perpetuated through ratooning.
•  The MLO is readily transmitted by sap inoculation and in the field it is transmitted through infected setts and perpetuated through crop ratooning.
•  The aphids are the vectors for this disease
•  This disease is also transmitted by -

            -Mechanically by cutting knife.
              -Insects (aphids, black hopper).  
-Dodder (root parasite).

FAVOURABLE CONDITIONS:

•  Dense planting.
•  Ratooning.
•  Presence of Insect.
•  Cloudy days.

DISEASE CYCLE: 

•  The primary spread of the phytoplasma is through diseased setts and cutting knifes.
•  The pathogen is transmitted secondarily by aphids viz., Rhopalosiphum maydis,Melanaphis sacchari and M. idiosacchari. 
•  Sorghum and maize serves as natural collateral hosts.

DISEASE MANAGEMENT:

   Cultural method:

•  Growing resistant varieties viz., Co 86249, CoG 93076 and CoC 22
•  Avoid ratooning if Grassy Shoot Disease incidence is more than 15 % in the plant crop
•  If disease symptoms are visible within two weeks after planting, such plants can be replaced by healthy plants.
•  Uprooted infected plants need to disposed of by burning them.

   Physical method:

•  Rogue out infected plants in the secondary and commercial seed nursery.
•  Treat the setts with aerated steam at 50°C for 1 hour to control primary infection.
•  Treating them with hot air at 540C for 8 hours and spraying twice a month with aphidicides.

   Chemical method:

•  Spray dimethoate @ 1ml in 1 litre of water to control insect vector
•  Apply pesticide methyl-demeton @ 2ml/lit of water for controlling aphids.

References:

Diseases of Field Crops:V.K Gupta & Y.S Paul (2002), Plant Diseases : R.S Singh , Plantix.net , apsjournals.apsnet.org , sugarcane.icar.gov.in , www.cabi.org, researchgate.net , agropedia, springer, eagri.org , agritech.tanu.ac.in , NIPHM, NCIPM.

Thank You!!

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