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Smut in sugarcane

Smut:

Causal Organism: Ustilago scitaminea

Primary spread of the disease is through infected setts and the secondary spread is through wind borne teliospore.

Symptoms:

  • The production of long whip like structure from the terminal bud of the stalk, which is black in colour covered by thin silvery membrane. This silvery membrane ruptures releasing millions of reproductive spores of smut fungus, present in the form of a powdery mass.
  • Losses due to smut range from 30 - 40% in plant crops and even up to 70% in ratoons. Sucrose content of infected cane is reduced to 3 - 7%.       

                                       smut  

 

 

 

 

 

 

 

 

Fig: Smut                                                      

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Smut of sugarcane

Smut, one of the easily recognized diseases of sugarcane with worldwide distribution, is caused by the Basidiomycetous fungus, (Ustilago scitaminea Sydow). Recently its name has been changed to Sporisorium scitamineum (Syd.) M. Piepenbr., M. Stoll et Oberw. It is present throughout India but its damage is severe in the tropical region, especially in the four southern states of Andhra Pradesh, Maharashtra, Tamil Nadu, Karnataka and Gujarat.

This seed piece transmissible disease has bimodal flush of producing whips. The first flush (arise due to primary infection) usually appears in May–June in the sub-tropical India, i.e., after the germination of the February-March planted/harvested crop. The second flush appears during October–November, mostly due to secondary infection which takes place during the summer months. In this situation whip emerges from the side buds.

Prior to the formation of whip, the infected plants start elongating (outgrowing others); leaves become narrow with pointed tips and come out at an acute angle at the long spaced nodes. From cane apex a long whip-like black structure comes out . The whip is initially covered by a thin silvery membrane of host origin, which eventually get ruptured exposing the black spore mass in the air. The exposed spores get disseminated by air current. Although the pathogen produces billions of teliospores per whip, the success rate of infection is very low and it seldom exceeds more than 3 per cent under normal cultivation practices. However, in a highly susceptible variety, if the planting material is fully infected, it may result in a total failure of the crop. Incidence of smut invariably increases in the ratoon crop due to the infection of subterranean buds, which germinates to from the ratoon tillers. 

  .sugarcane Smut whip