Seed Health Management for Better Productivity - Govind Ballabh ...

(Seed Health Management for Better Productivity)Smuts, Bunts and Ergots their Significance and Management in SeedCropR.C. SharmaSeed Technology Centre, Punjab Agriculture University, LudhianaSmuts, Bunts and Ergot are important seed borne diseases, the primary inoculum of whichis carried in or on seed (smuts and bunts) or go as an admixture (ergot) with the seed.Smuts and BuntsThe word smut means a soft, charcoal-like substance or a sooty powder. The organismscausing smuts and bunts belong to order Ustilaginales. The resting spores, commonly known assmut spores are thick-walled and on germination produce septate or aseptate promyceliumbearing basidiospores (called sporidia) laterally and apically or in groups at the apex of thepromycelium. Sporidia are haploid and when they germinate, a haploid mycelium (primarymycelium) is produced which later gets dikaryotic. This mycelium invades the host plant, usuallykeeps pace with the meristematic region of the host.Types of infections in SmutsThe infection by the smuts fungi may be primary or secondary, systemic or local,depending upon the species in question. On the basis of primary infection the following three typesmay be remembered for better control of these diseases:1. Seedling infection: The smut spores are usually smooth-walled, externally seed- borne,and germinate along with the germinating seed to cause seedling infection. The infection ofseedling takes place before its emergence out of the soil. Change of haplophase todiplophase occurs before infection (Flag smut and covered smuts).2. Floral or blossom infection or Intra-seminal Infection: The spores are usually roughwalledand wind-borne to fresh flowers where they germinate to cause infection of theovary after diplodization. The binucleate hyphae reach the embryo, ramify, and becomedormant with maturity of the seed. The infection is thus carried internally with the seed andwhen the latter germinates the fungus also grows up and finally appears as black powderymass in the inflorescence (Loose smut diseases).3. Shoot Infection: This is usually localized infection. The spores may fall on the surface ofthe host, germinate, and cause infection of young buds, young flowers, developing seeds,or may fall on the ground, perennate there ultimately germinating next year causinginfection of the host parts through wind-borne sporidia (Karnal bunt of wheat and Kernelsmut of rice).- 121 -