Screening groundnut cultivars for resistance to Aspergillus flavus, Aspergillus parasiticus, and aflatoxin contamination
1989
Pettit, R.E. | Azaizeh, H.A. | Taber, R.A. | Szerszen, J.B. | Smith, O.D.
Screening groundnut cultivars for aflatoxin resistance involves a consideration of the environmental conditions that favor invasion of Aspergillus flavus. The plant tissues penetrated, time of penetration, and the physical and biochemical factors that restrict invasion and aflatoxin formation also require consideration. Aspergillus-invaded cotyledonary leaves may be a primary source of inoculum. Developing shells of all cultivars examined were easily invaded; but penetration through the shell into the pod cavity varied with cultivar. Pods that formed lignified sclerenchyma bands early in their development were less susceptible to hyphal penetration than those without such bands. Kernel invasion is influenced by features of the hilum and seed coat. Small, covered hila, and compact seed coats with a thick wax deposition are important in relation to resistance. The content of the seed coats and pods varied among cultivars. Inhibitory compounds in the cotyledons slow fungal growth or inhibit aflatoxin formation. Tannin-like compounds (umbelliferone and methylcatechol) found in some groundnut seed coats were found to inhibit A. flavus growth and aflatoxin formation. Electrophoretic separation under sodium dodecyl sulfate denaturation revealed the presence of 20 polypeptides that vary among cultivars differing in susceptibility to A. flavus. Isolation of various plant constituents to detect the presence of specific proteins, tannin-like compounds, lignins, phytoalexins, and other compounds may correlate with levels of resistance and should be helpful in screening cultivars
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