COLLETOTRICHUM GRAMINICOLA: PHYSIOLOGIC SPECIALIZATION, CHARACTERIZATION OF RACES, AND THE EFFECT OF ANTHRACNOSE LEAF BLIGHT ON GRAIN YIELD OF SORGHUM
Abstract
Nine sorghum isolates of Colletotrichum graminicola (Ces.) Wils. from different geographical areas were tested for pathogenicity on six sorghum cultivars. Based on the differential responses of two of the six sorghum cultivars, the nine isolates were grouped into three physiological races designated as races 1, 2, and 3. The three isolates grouped as race 2 were the most aggressive ones. The aminopeptidase profiles and electrophoretic patterns of soluble proteins were determined for fourteen isolates of C. graminicola from sorghum, corn, and barnyard grass. The conventional filter fluorometer and the laser-based assay procedures were used to determine the aminopeptidase specificities of the isolates on the beta-naphthylamide substrates. Analysis of the aminopeptidase filter fluorometer profiles permitted separation of isolates according to their hosts, but separation of the sorghum isolates according to their virulence on differential sorghum lines was not possible. The aminopeptidase laser procedure allowed separation of isolates according to their hosts, as well as separation of the sorghum isolates into three groups which correlate with their virulence. Although the sorghum isolates varied in their protein patterns, their separation into groups which correlate with their virulence on differential sorghum cultivars was not possible. Protein patterns of the corn and barnyard grass isolates were almost similar. Analysis of the individual effects of nine sorghum isolates of C. graminicola on grain yield of four sorghum cultivars showed that the amount of loss in yield due to anthracnose leaf blight (ALB) is influenced by aggressiveness of isolate, sorghum cultivar, and environmental conditions that affect anthracnose development. A significant linear relationship between ALB severity and loss in grain yield was established. Highly significant (P < 0.01) positive correlations between percent loss in grain yield or percent loss in 100-seed weight and ALB severity occurred. The highly significant (P < 0.01) positive correlations between percent loss in grain yield and percent loss in 100-seed weight indicate that ALB reduces grain yield of sorghum largely by decreasing seed weight. The sorghum, corn, and barnyard grass isolates of C. graminicola differed in their pathogenicity and were host specific. The sorghum isolates caused susceptible responses only on sorghum, the corn isolates only on corn, and the barnyard grass isolate only on barnyard grass.
Degree
Ph.D.
Subject Area
Plant pathology
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