Seed-borne fungi associated with cowpea and rice seed and their possible control by seed sorting

Abstract

The objective of the study was to examine the effectiveness of different seed sorting techniques for improving seed health of cowpea and rice seed. Two separate trials were conducted. In each trial, a sample of 1,400 seeds was drawn from which sets of 200 seeds were each sorted by hand, floated in water (as a standard), floated in 10% and 15% salt solutions (to separate floated and sunken seeds), dressed with Benlate (1g ai/kg), Mancozeb (2g ai/kg) (positive control) and the last set was an unsoned control. In comparison to the unsorted seeds (control), all the cowpea treatments significantly reduced the incidence of Fusarium moniliforme, Cladosporium sp., Fusarium poae, Nigrospora sp., Phoma sp., and Phomopsis vexans. Seeds floated in 15% salt solutions had significantly less fungal incidence than hand sorted seed and did not differ from the seed dressed treatments. Seeds skimmed off the three salt solutions as floated seed were all infected with F. moniliforme and F. semitectum and majority got rotten upon blotting. For rice, Bipolaris oryzae, Phyrularia were the predominant seed-borne pathogens. The lowest incidence of the seed-borne fungal pathogens was recorded in fungicide seed dressed samples followed by 15% and 10% salt floated samples. Hand sorted samples had similar incidence of fungal flora as the unsorted samples.