Ear Resistance of Maize Inbreds to Field Aflatoxin Contamination1

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Abstract
A study was conducted to identify resistant genotypes for incorporation into a breeding population for recurrent selection. An eight‐line diallel of sweet corn (Zea mays L.) single crosses and a nine‐line diallel of dent single crosses were grown in replicated experiments for 3 years. Ears were knife inoculated at 20 days after full silk with an Aspergillus flavus Link (NRRL 3357) spore suspension, and grain was evaluated at maturity for total aflatoxin contamination. The Grilling Model I, Method 4, was used to partition genetic variation. General combining ability (GCA) was significant among inbreds in the dent and sweet corn diallels. No specific combining ability (SCA) effects were detected in either of the analyses combined over years, but an SCA ✕ years interaction occurred in the analysis of sweet corn crosses. The GCA and SCA effects were significant in two of three dent corn analyses within years. The 1981 analysis revealed significant GCA and SCA effects for the sweet corn diallel. Those analyses in years with very low aflatoxin contamination yielded nonsignificant GCA effects. Two or three inbreds within each set performed well enough as single crosses to be used as sources of resistance in breeding populations. Present methods of inoculation do not always produce enough contamination to identify resistant genotypes. Because of this and the cost of analyses, additional evaluations are often needed to efficiently identify desirable genotypes.