South African Journal of Science
On-line version ISSN 1996-7489
DUBE, Ernest; SIBIYA, Julia and FANADZO, Morris. Early planting and hand sorting effectively controls seed-borne fungi in farm-retained bean seed. S. Afr. j. sci. [online]. 2014, vol.110, n.11-12, pp. 01-06. ISSN 1996-7489. http://dx.doi.org/10.1590/sajs.2014/20130342.
Home-saved bean (Phaseolus vulgaris L.) seed can be hand-sorted to remove discoloured seed, thereby reducing the level of contamination by certain seed-borne fungi and improving seed germination. In this study, the effect of planting date on the infection and discolouration of bean seed by seed-borne fungi was investigated in order to improve the quality of hand-sorted, farm-retained bean seeds used by resource poor smallholder farmers. The germination quality and level of seed-borne fungi in hand-sorted first-generation bean seed harvested from an early-, mid- and late-summer season planted crop was therefore assessed. The highest percentage of discoloured seed (68%) was obtained from the mid-summer season planting. Non-discoloured seed from early- and late-season plantings had significantly (o<0.001) higher normal germination (82% and 77%, respectively) than that from the mid-season planting date (58%). Irrespective of planting date, unsorted seed and discoloured seed had higher levels of infection by Fusarium spp. and Phaeoisariopsis spp. than the non-discoloured seed. Removal of discoloured seed by hand sorting eliminated Rhizoctonia spp. from all seed lots. Farmers can eliminate this pathogen by simply removing discoloured seed. Non-discoloured seed from the early-planted crop had the lowest level of infection by Fusarium spp. and Phaeoisariopsis spp. The results indicate that planting date is an important consideration in improving the quality of hand-sorted farm-retained bean seed.
Keywords : common bean; planting date; seed-borne fungi; seed quality; visual sorting.