Location: Corn Host Plant Resistance ResearchTitle: Aflatoxin accumulation in a maize diallel cross containing inbred lines with expired Plant Variety Protection
Submitted to: Agronomy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/4/2021
Publication Date: 11/11/2021
Citation: Smith, J.S., Williams, W.P. 2021. Aflatoxin accumulation in a maize diallel cross containing inbred lines with expired Plant Variety Protection. Agronomy. 11(11):2285. https://doi.org/10.3390/agronomy11112285.
Interpretive Summary: Aflatoxins are toxic compounds produced by the fungus Aspergillus flavus. Aspergillus flavus is a pathogen of corn, especially in the Southeast. When corn ears are infected by Aspergillus flavus, the grain can be contaminated with aflatoxin. Due to its toxicity, aflatoxin is regulated and contamination can reduce the value of a farmer's grain after harvest. Inbred lines with genetic resistance to aflatoxin contamination have been bred, but these lines generally mature later than desired and they do not make high yielding hybrids. Crossing these disease resistant lines with elite inbreds would generate useful breeding populations aimed at combining disease resistance and yield potential. Inbred lines developed by private industry are proprietary and protected by Plant Variety Protection (PVP) law. This PVP protection expires after 20 years, and these lines (ex-PVPs) become publiclly available to breeders. This study evaluated a set of seven expired PVP inbreds and three disease resistant lines in order to identify promising ex-PVP lines. A set of 45 hybrids was formed by crossing every combination of the 10 inbreds. The disease resistant lines developed by the ARS (Mp313E, Mp715 and Mp717) were the only lines that reduced aflatoxin in hybrids. The ex-PVP line F118 was the most promising of the ex-PVPs. It was the only ex-PVP that did not significantly increase aflatoxin in hybrids and the only ex-PVP to significantly increase yield in its hybrids. This line could be crossed to the disease resistant lines in order to breed new inbred lines with disease resistance and increased yield potential.
Technical Abstract: In-field infection of maize (Zea mays L.) ears by the fungus Aspergillus flavus Link:Fr causes pre-harvest aflatoxin contamination of maize grain. Germplasm lines with host-plant resistance to aflatoxin accumulation are available to breeders, but these lines often possess undesirable agronomic characteristics. Industry lines with expired Plant Variety Protection (ex-PVP lines) are potential a source of elite germplasm available to public maize breeders. A diallel cross containing three aflatoxin accumulation resistant germplasm lines and seven ex-PVP lines was evaluated in replicated trials for yield and aflatoxin contamination after artificial inoculation. The resistant germplasm lines Mp313E, Mp715, and Mp717 were the only lines with significant general combining ability (GCA) for reduced aflatoxin accumulation. Of the ex-PVP lines evaluated, the Stiff-Stalk line F118 was the most promising line to use in breeding crosses. Based on its GCA, it was the only ex-PVP line that did not significantly increase aflatoxin and the only ex-PVP line that significantly increased yield.