SEVERITY OF LEAF STREAK (Stenocarpella macrospora) AND ITS RELATION WITH PATHOGEN INCIDENCE AND GERMINATION ON GRAINS OF COMMERCIAL AND EXPERIMENTAL MAIZE HYBRIDS

Abstract

The fungus Stenocarpella macrospora (Sin. Diplodia macrospora) is one of the pathogens associated with the stalk and ear rots complex, damping off and large foliar lesions in susceptible hybrids. The objective of this study was to correlate the severity of leaf streak (Stenocarpella macrospora) with the pathogen incidence in grains, as well to evaluate the effect of this incidence on grain germination of different maize hybrids. For that purpose, a trial was carried out at the experimental field of Dow AgroSciences in Uberaba (MG). Sixteen hybrids in 2002/2003, and 20 in 2003/2004 were evaluated for leaf streak severity, under natural infection in the field, in a randomized complete block design with two replications, and experimental plot consisting of four 4m-long rows. The two central rows of each plot were graded for disease severity. After harvested, a grain sample (1Kg) was taken from each plot to seed health (blotter test with freezing method) and germination (germination roll method) tests. In both experiments, results showed no positive correlation between disease severity and pathogen incidence on grains, suggesting that the high level of severity of the foliar phase of the disease cannot be taken as an indication of the incidence of the fungus on grains. A negative correlation between the incidence of the pathogen on grains and germination, and a positive correlation between pathogen incidence and the percentage of non-germinated grains were observed, indicating that S. macrospore affects the physiological quality of maize grain.

Keywords

• Grain rot
• Diplodia macrospora
• health test
• severity