Fungi associated with seeds of three varieties of sorghum grown in Botswana and its control in vitro using fungicide and plant extract treatment

Seeds of three sorghum varieties namely Segaolane, Phofu and SNK-3939 obtained from different locations in Botswana were used for detection of seed-borne fungi and their possible control by botanical and fungicides. Four hundred seeds of each variety were surface sterilized with 2% sodium hypochlorite solution before placing them on moist blotter (10 seeds/90cm Petri plate), and incubated for seven days at 22±2 o C for 12 hours under continuous light and alternating with 12 hours darkness. Eight seed-borne fungi were recovered. These were Aspergillus flavus, A. niger, Alternaria alternate, A. infectoria, A. solani, Curvularia lunata, Fusarium moniliformae and F. oxysporum. Fusarium species were dominant fungi recovered from the seeds, followed by Alternaria and Aspergillus species. The fungi detected resulted in decay and rotting of seeds, and thereby reducing percentage germination of seeds (3%, 29% and 58% seed germination in Segaolane, SNK – 3939 and Phofu respectively). Seeds treated with benlate and the aqueous leaf extract of Melia azedarach effectively controlled seed-borne fungi, and enhanced seed germination to over 90% as compared to captan (75%).copper oxychloride (60%) and Dithane M 45 (50%) as compared to non-treated seeds (20%).