INCIDENCE AND VARIABILITY REACTION OF SUGARCANE SMUT (USTILAGO-SCITAMINEA SYD) ISOLATES IN GREENHOUSE AND LABORATORY TESTS IN NIGERIA

The reaction of twelve isolates of Ustilago scitaminea Syd. from diffe rent locations on nine farmers' fields and three estate and experiment al farms was tested on five commercial sugarcane varieties in the gree nhouse by inoculation of smut teliosperes with a hypodermic needle. Si milarly in vitro growth of the isolates on sucrose agar (SA) and Potat o Dextrose agar (PDA) at 30 degrees C for 45 days was successfully car ried out. Smut incidences on the canes inoculated ranged from 39-96%. The isolates from Plateau (Shendam and Mangu) produced all the growth sectors (a creamy convoluted, brown-black, white mycelial, and yeast-l ike) on both the SA and PDA media. The other isolates from Kaduna, Nig er, Benue, Kwara States and the Federal Capital Territory (FCT), Abuja did not produce the creamy convoluted cultural characteristic on both the SA and PDA media. No significant difference (P less than or equal to 0.05) was obtained between Shendam and Mangu isolates but signific ant differences were obtained between these isolates and the rest. In this study Shendam and Mangu isolates elicited high virulence and path ogenicity reaction on both the agar media and sugarcane varieties eval uated. We thus ascribe them as race X while the rest have been denoted as belonging to race Y.