Role of seed lipids on Aspergillus parasiticus growth and aflatoxin production

Seeds of crops with differing lipid content (groundnut (Arachis hypogaea L), paddy (Oryza sativa L), sorghum (Sorghum bicolor (L) Moench), cowpea (Vigna unguiculata L Walp) and green gram (Vigna radiatus L Wilczek)) were screened for their ability to support growth and aflatoxin B1 (AFB1) production by Aspergillus parasiticus NRRL 2999. Groundnut, with the most lipids, supported greatest AFB1 production. With all crops except for sorghum and paddy, powdered seed material (PSM) supported more AFB1 production than their respective defatted powdered seed material (DPSM). When A parasiticus was grown on Czapek Dox agar amended with PSM and DPSM of different seeds with differing lipid contents, A parasiticus colonies were always larger on PSM-than on DPSM-supplemented medium of the same seed. However, mycelial dry weight was only greater on media supplemented with groundnut, cowpea or green gram PSM. Growth and aflatoxin production by A parasiticus was also compared in Czapek Dox broth amended with seed coats, cotyledons and embryonic axes of groundnut kernels. The cotyledons of groundnut, with most lipids, supported the greatest production of AFB1. Apart from media supplemented with embryonic axes, PSM again supported more growth and AFB1 production than DPSM of the same portion of the kernel. Seed lipids thus seem important in determining growth and AFB1 production by A parasiticus.