New Bunt of Wheat (Karnal Bunt of Wheat)

History and Importance:

  • Reported in 1931 on wheat, grown near Karnal, India
  • Found in all major wheat-growing states of India, as well as in Pakistan, Iraq, Mexico, and Afghanistan
  • Losses ranging from 20-40%

Etiology:

Causal organism: Neovosia indica

Order: Ustilaginales

Family: Tillitiaceae

Symptoms:

  • Only few seeds per head infected
  • Not all heads on a single plant are infected
  • Disease is difficult to detect in the field
  • Only a part of the germ end converted into a black powdery spore mass,
  • Extreme cases, the entire kernel is converted into spores
  • Rotten fish smell from the diseased field

Disease cycle:

  • Smut fungus Tilletia indica (also known as Neovossia indica)  spread by spores
  • Spores can be carried in soil and on a variety of surfaces, including seed and other plant parts & also windborne
  • Uplifted during the burning of wheat fields, and areas downwind may become contaminated if the spores remain viable

Epidemiology:

  • 15–25° C, RH >82 %

Management:

  • Seed treatment with PCNB and carboxin + thiram (Vitavax-Thiram)
  • Disinfesting seeds in a 1.5% solution of sodium hypochlorite (i.e., 1 part of household bleach to 2 parts of water) plus Tween 20 with agitation for 10 minutes followed by rinsing
  • Resistant varieties,Watan, Sehar, Bk-2000

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