RELATIONSHIP BETWEEN HEAD BLIGHT SYMPTOMS OF FUSARIUM-ROSEUM VAR CULMORUM AND YIELD LOSSES IN WHEAT

Four winter wheat cultivars were inoculated in field tests by Fusarium roseum var culmorum over a 4-yr period. Several spore concentrations of the inoculum were used each year. The severity of the disease was e valuated using the number of damaged spikelets at the early dough grow th stage and the percentage of visually infected seeds at harvest. Yie ld and 1 000 grain weight losses were measured with reference to an un inoculated control A significant correlation was found between the num ber of damaged spikelets and the number of visually infected seeds tog ether with an effect of the variety and the year. On a linear basis, b ecause of a weak year effect, the decrease in 1 000 grain weight is be tter predicted using the number of visually infected seeds than the nu mber of damaged spikelets. There is a trend for non-linear response cu rves for 2 varieties. The use of field evaluation of severity of the d isease and tolerance of varieties are discussed.