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The inhibitory e!ects of six fungicides on macrospore germination and production of secondary conidia of Claviceps africana were studied. E!ects of these fungicides on germination of sorghum seed also were determined. Panicles from male-sterile sorghums with honeydew exudate were harvested from the USDA-ARS Research Farm, Isabela, Puerto Rico in the Spring of 1997. Honeydew exudate-infested panicles were used as inoculum to infest ergot-free sorghum seed. Seeds were placed on 1 and 2% water agar containing 100 mg/l each of streptomycin sulfate and ampicillin and were also plated on soil. They were incubated at 21}223C, 16 h of light. At 24 and 48 h, samples were examined under a microscope, equipped with 50] and 100] objectives, for germination of macroconidia and the formation of conidiophores and secondary conidia on both seed, soil, and agar surfaces. Samples also were evaluated for seed germination. Abundant conidiophores with conidia were observed over the entire seed surface of (control) honeydew-infested seed while none were observed on untreated control seed. Fungicidal e!ects and seed germination results showed that captan (Captan 400 ’ ) and thiram (42-S Thiram ’ )e !ectively inhibited conidiophore production and secondary conidia formation without severely reducing viability of the sorghum seed. ( 1999 Elsevier Science Ltd. All rights reserved. |
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