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Institute of Agricultural & Environmental Research Tennessee State University |
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Seminar Series Abstract
Seed-borne Diseases Of Dogwood And Their Control Emmanuel Nnodu
Tennessee State University, Institute of Agricultural & Environmental Research, Otis L. Floyd Nursery Research Center, McMinnville, TN
Many fungi invade dogwood seeds during their developmental stages and during harvest and storage. They cause poor seed germination and high post-emergence mortality. Seed-borne fungi were isolated from dogwood seeds acquired from Tennessee, North Carolina, Massachusetts, Alabama, Pennsylvania and Montana. The seeds were surface-sterilized in 10% sodium hypo chlorite, washed in three changes of sterile distilled water and then plated in potato dextrose agar plates to which chloramphenicol was added to inhibit growth of bacteria.The plates were incubated for 7 days at 25 C. Colletotrichum acutatum, Curvularia affinis, Botyosphaeria dothidea, Fusarium sp.,Alternaria alternata,Pestalotia sp.,Naranus cryptomeriae, Pithomyces sp., Epicocum purpurescens, Penicillum negundus and Motierella sp. were pathogenic to dogwood. The pathogenicity of the fungi were confirmed by laboratory tests. Wilting occurred when roots of clean dogwood seedlings were immersed in suspensions of the respective fungi for 30 minutes and grown in sterile soil. The control seedlings immersed in sterile water did not wilt. Also by Bavendamn reaction where the fungi produced strong violet coloration in 2.5% malt extract agar to which 0.1% of Guaiacol was added indicating the ability of the fungi to produce phenol oxidase for depletion of polysaccharides and lignin in plants. A.alternata and B. dothidea were the most frequently isolated fungi.
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