Speakers - 2026

Title: Biocontrol efficacy of alternaria alternata on some sorghum (sorghum bicolor (l) moench) varieties infected with colletotrichum graminicola (anthracnose)

Abstract

Anthracnose caused by Colletotrichum graminicola is one of the diseases impacting on the yield of sorghum in Nigeria. This study was carried out to evaluate the efficacy of Alternaria alternata on some sorghum (Sorghum bicolor (L). Moench) varieties infected with C. graminicola. The fungi were isolated from anthracnose infected sorghum leaf and cultured on potato dextrose agar. They were identified morphologically by conidia and colony structures. Antagonistic effect of A. alternata against C. graminicola was carried in vitro on PDA using single and dual culture technique. Secondary metabolites were extracted from methanolic extracts of A. alternata and characterized using gas chromatography-mass spectrometry analysis. The efficacy of methanolic extracts (0.5, 1.0 and 2.0 mg/ml) of A. alternata against C. graminicola infected Sorghum bicolor varieties was carried out in vivo in the screen house. The results showed that both A. alternata and C. graminicola could be distinguished based on colony and conidial morphology. A. alternata inhibited the growth of C. graminicola on PDA and the former outgrew the latter 14 days after incubation. Twelve bioactive compounds synthesized by A. alternata were characterized according to their peak area, retention time, molecular and molecular weight. Also, 2.0 mg/ml methanolic extract of A. alternata significantly reduced anthracnose incidence and severity in sorghum. The varied concentrations of methanolic extracts of A. alternata also significantly improved the growth and yield of sorghum infected with anthracnose. Infected SAMSORG 42 treated with A. alternata extract had the tallest plants and largest number of tillers. However, SAMSORG 44 had the highest number and heaviest panicles, and heaviest seeds when treated with A. alternata extracts. The results of this study revealed that methanolic extracts of A. alternata could be used in the management of sorghum anthracnose, probably due to the presence of secondary metabolites.

Keywords; Colletotrichum graminicola, Alternaria alternata, methanolic extracts, Sorghum bicolor, growth and yield