Abstract
A grass Ischaemum ciliare Retz. (Syn. I. indicum Houtt. Mem.) growing in the sugar cane fields at Cannanore, Kerala State, was identified as a collateral host for sugar cane smut. The fungus causing grass smut was identified as Sphacelotheca sorghii (Link.) Clinton. It produces ovaricolous smut sori on the grass and natural incidence of such sori was common in the sugar cane fields. Teliospores of S. sorghii when artificially inoculated on clones of sugar cane genotypes produced typical culmincolous whips like those produced by Ustilago scitaminea Syd. infection. Teliospores of S. sorghii produced about 30-38% infection in sugar cane compared with 7-15% with U. scitaminea teliospores inoculation on susceptible cultivars under field conditions. Variation in telioscope size of S. sorghii infecting the grass and the same after whip production in sugar cane was observed. Sphacelotheca sorghii teliospore infection and colonization on sugar cane was identical to U. scitaminea. Profuse intercellular mycelial growth and haustoria production in apical meristems of growing shoots were noticed seven days after inoculation. Serological studies were carried out using U. scitaminea polyclonal antiserum produced against dikaryotic mycelium. Both smut fungi showed a close serological relationship. The results are discussed with respect to the role of S. sorghii adapted to the weed host and sugar cane on the secondary spread of smut in the fields of sugar cane germplasm.
