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United States Department of Agriculture

Agricultural Research Service

Research Project: Genetic Improvement of Maize with Enhanced Resistance to Aflatoxin and Insects

Location: Corn Host Plant Resistance Research

Title: Parental genome contribution in maize DH lines derived from six backcross populations using genotyping by sequencing and its relationship with testcross performance

Authors
item Ogugo, V. -
item Semagn, K. -
item Beyene, Y. -
item Runo, S. -
item Olsen, M. -
item Warburton, Marilyn

Submitted to: Euphytica
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 11, 2014
Publication Date: N/A

Interpretive Summary: The improvement of corn lines by plant breeders involves making crosses between parents with good traits, and then selecting among the progeny for those who have the best new combination of traits. At the same time, the undesirable traits that were present in the parents must not be present in the new breeding lines derived from the progeny of these new crosses. The percentage of genes contributed from each parent may be important for determining which of the progeny will perform well for important traits such as yield under drought and Anthesis Silking Interval (a measurement of drought tolerance). Molecular characterization maize lines derived from new crosses and estimation of parental genome contribution (PGC) may be useful for this process of determination. Six populations created by crossing two drought tolerant lines with three disease resistant lines were genotyped with 97,190 polymorphic markers with the objectives of: i) understanding genetic purity, genetic distance and relationships among 417 maize lines from these six populations; ii) estimating PGC of the lines derived from different parents; and iii) understanding the correlation between donor parent introgression and performance for grain yield and anthesis-silking interval (ASI) under managed drought and optimum environments. Donor parent contribution was not significantly different among the genetic background of the three recurrent parents. However, donor genome introgression was higher than expected in 82% of the progeny lines, possibly due to artificial selection. Donor parent introgression up to 32% showed significant positive correlation with grain yield under drought and optimum environments and negative correlation with ASI under drought. This suggests the possibility of introducing undesirable genes when introgression levels exceeded 32%, and therefore lines with less than 32% PCG from the donor parent should be selected. The results also suggest that the two donor parents are good sources for improving maize for drought tolerance and high yield potential in sub-Saharan Africa.

Technical Abstract: Molecular characterization of doubled haploid (DH) maize lines and estimation of parental genome contribution (PGC) may be useful for choosing pairs of DH lines for hybrid make up and new pedigree starts. Six BC1-derived DH populations created by crossing two donor with three recurrent parents were genotyped with 97,190 polymorphic markers with the objectives of: i) understanding genetic purity, genetic distance and relationship among 417 maize DH lines; ii) estimating PGC of the DH lines derived from different genetic backgrounds; and iii) understanding the correlation between donor parent introgression and testcross performance for grain yield and anthesis-silking interval (ASI) under managed drought and optimum environments. The DH lines were 97% genetically pure, with <2% heterogeneity. Two DH lines showed heterogeneity >5%, and require further purification. Genetic distance between pairwise comparisons of the 417 DH lines ranged from 0.055 to 0.457; only 0.01% showed a genetic distance <0.100, indicating large genetic differences among the DH lines. Donor parent contribution was not significantly different among the genetic background of the three recurrent parents. The average donor and recurrent PGC across all 417 DH lines was 31.7% and 64.3%, respectively. Donor genome introgression was higher than expected in 82% of the DH lines in the BC1 generation, possibly due to artificial selection during the DH process, during the development of F1 or BC1 seed, or during initial agronomic evaluation of the DH lines. Donor parent introgression up to 32% showed significant positive correlation with grain yield under drought (r=0.312, p <0.001) and optimum (r = 0.142, p <0.050) environments but negative correlation with ASI under drought (r = -0.276, p <0.001). Our study revealed high genetic distance among the DH lines and significantly higher donor parent genome contribution than expected. Up to 32% of donor parent introgression was significantly correlated with grain yield and ASI, suggesting the possibility of introducing undesirable genes when introgression levels exceeded 32%. The results also suggest that the two donor parents are good sources for improving maize for drought tolerance and high yield potential in sub-Saharan Africa.

Last Modified: 9/23/2014
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