Increasing sorghum yields by seed treatment with an aqueous extract of the plant Eclipta alba may involve a dual mechanism of hydropriming and suppression of fungal pathogens
Background Soaking of sorghum seeds for six hours in an aqueous extract of Eclipta alba has been shown to increase the yield of sorghum in field experiments. The effect on yield is known to depend on field location and a mechanism involving pathogen suppression has been proposed. However, it has not been clear to which extent the same effect can be obtained by soaking of seeds in pure water (hydropriming). To address this question, fifty eight field tests were conducted comparing no treatment of seeds, hydropriming and treatment with plant extract. Experiments were distributed over three years in Burkina Faso on three locations previously showing a positive yield response to the plant extract. Results Despite strong variation across locations and years, a mean yield increase of 19.6% was found for hydropriming compared to no treatment (p?.018). For the plant extract, an additional yield increase of 32.1% was found (p?.016) corresponding to a total increase of 51.7%. In a subset of 15 experiments, a positive, but non-significant correlation was observed between the additional effect of the plant extract and the effect of a binary pesticide, Calthio C. Significantly, however, the E. alba extract reduced the number of seedlings infected by seed-borne filamentous fungi (p?.05). A reduction of infection by more than five-fold was found for the E. alba extract compared to hydropriming and included potential pathogens of sorghum: Epicoccum sorghinum and Curvularia spp. Conclusion Using 6-hours of soaking, hydropriming was an inherent component of seed treatment with the E. alba extract and contributed significantly to the overall observed increase of yield and emergence. An additional yield increase was caused by factor(s) derived from the plant, E. alba, and may involve suppression of pathogenic fungi.