Mapping QTL for aflatoxin accumulation resistance in two populations containing resistant maize inbred Mp717

Authors: Smith, Jesse; Williams, William; Warburton, Marilyn; WINDHAM, GARY - Retired ARS Employee; XU, WENWEI - Texas A&M Agrilife; BHATTRAMAKKI, DINAKAR - Corteva Agriscience

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/12/2021
Publication Date: 2/14/2022
Citation: Smith, J.S., Williams, W.P., Warburton, M.L., Windham, G.L., Xu, W., Bhattramakki, D. 2022. Mapping QTL for aflatoxin accumulation resistance in two populations containing resistant maize inbred Mp717. Crop Science. 62(2):780-791. https://doi.org/10.1002/csc2.20695.
DOI: https://doi.org/10.1002/csc2.20695

Interpretive Summary: The fungus Aspergillus flavus produces aflatoxin which is toxic to livestock, pets, and wildlife and causes cancer in humans. Corn grain contaminated with aflatoxin is markedly reduced in value. USDA-ARS scientists at Mississippi State have developed corn germplasm lines with resistance to aflatoxin accumulation. To identify chromosomal regions known as quantitative trait loci (QTL) associated with resistance, one of these lines, Mp717, was crossed with two susceptible lines, Va35 and PHW79, to produce two bi-parental QTL mapping populations: Mp717 x Va35 and Mp717 x PHW79. The families making up the populations were evaluated for resistance to aflatoxin accumulation following artificial inoculation in four environments. For the Mp717 x Va35 population, alleles associated with resistance to aflatoxin accumulation contributed by Va35 explained a larger cumulative portion of the phenotypic variation than those contributed by Mp717 in all four environments. When the data was combined across environments, Mp717 contributed the beneficial allele for 4 QTL, but they individually explained only 2.5 to 5.4% of the phenotypic variance. In contrast, Mp717 was the source of the resistance allele for the vast majority of the QTL observed in the Mp717 x PHW79 population in all environments. When the data was combined across environments, Mp717 was the source of the resistance allele for 8 QTL that individually explained 3.5 to 8.7% of the phenotypic variance. Three medium effect QTL were observed in that population that individually explained 7.7 to 8.7% of the phenotypic variance. However, none of those QTL were observed in the Mp717 x Va35 population. Due to the small effect size of most observed QTL and the inconsistency across genetic backgrounds of the few medium-effect QTL that were detected, it was concluded that the no resistance QTL suitable for the marker-assisted introgression of the resistance present in Mp717 were detected in either of these populations.

Technical Abstract: Mp717, a maize germplasm line resistant to aflatoxin accumulation, served as the resistant parent in two bi-parental QTL mapping populations: Mp717 x Va35 and Mp717 x PHW79. Both populations were phenotyped for concentration of total aflatoxins following artificial inoculation in replicated field trials grown in four environments. For the Mp717 x Va35 population, QTL for which the beneficial allele was contributed by Va35, not Mp717, explained a larger cumulative portion of the phenotypic variance than QTL for which the beneficial allele was contributed by Mp717 in all four environments. When the data was combined across environments, Mp717 contributed the beneficial allele for 4 QTL, but they individually explained only 2.5 to 5.4% of the phenotypic variance. In contrast, Mp717 was the source of the resistance allele for the vast majority of the QTL observed in the Mp717 x PHW79 population in all environments. When the data was combined across environments, Mp717 was the source of the resistance allele for 8 QTL that individually explained 3.5 to 8.7% of the phenotypic variance. Three medium effect QTL were observed in the Mp717 x PHW79 population that individually explained 7.7 to 8.7% of the phenotypic variance. However, those QTL were not observed in the Mp717 x Va35 population. Due to the small effect size of most observed QTL and the inconsistency across genetic backgrounds of the few medium-effect QTL that were detected, it was concluded that no resistance QTL suitable for marker-assisted introgression of the resistance present in Mp717 were detected.