Iterative germination and innovative techniques for the production and inoculation of secondary conidia of sorghum ergot (Claviceps africana)

Abstract

Five methods of harvesting pure secondary conidia were attempted, but only one was successful. The only successful method involved moving air across the surface of water agar plates or moist soil on which secondary sporulation was occurring at 0.2 – 3 m/s. Among the inoculation techniques, brushing the secondary conidia on to the wet stigma gave maximum ergot infection (80%) followed by brushing the secondary conidia on to the dry stigma (77%). Conidia of Claviceps africana produced up to seven generations of sibling conidia. The length and width of secondary conidia showed a reduction in size from 10.92 – 10.13 µm and 5.49 – 5.13 µm, respectively, across generations. However no definite trend in decline in size of secondary conidia was evident. The optimum temperature range for germination of secondary conidia of Australian isolates of C. africana is between 14.6 and 20°C.