Screening of sorghum grain biorefinery by-products for growth inhibition of two common postharvest pathogens of mango

Plants have protective phytochemicals and may also produce phytoalexins in response to fungal attack. Phytochemicals from food waste sources may have potential application as crop protectants. Condensed Distillers' Solubles (CDS) and Dried Distillers' Grains (DDG) are by-products of ethanol production from sorghum grain. This study tested the inhibitory effects of these compounds on growth of two postharvest fungal pathogens of mango, Colletotrichum gloeosporioides (Cg) and Lasiodiplodia theobromae (Lt) using Petri dish growth inhibition assays. The EC₅₀, (Effective Concentration at which mycelial growth is inhibited by 50%), for Cg of CDS was 10.4% v/v of the crude extract. The EC₅₀ of DDG for Cg and Lt was 8.4 and 19.1 mg mL^-1, respectively. Mycelial growth of Lt was significantly increased by CDS at 25, 10 and 1% v/v at four and five days after incubation, but after 6 days of incubation there was no significant difference from controls and lower CDS concentrations. We are now testing the sorghum grain biofuel by-products as postharvest treatments and field sprays, to assess their potential in reducing losses by postharvest diseases in commercial horticultural production.