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Title: Weighing in on a method to discriminate maize haploid from hybrid seed

item SMELSER, ANDREW - Mike Brayton Seeds (MBS) Genetics, Llc
item BLANCO, MICHAEL - Retired ARS Employee
item LÜBBERSTEDT, THOMAS - Iowa State University
item SCHECHERT, AXEL - Strube Research Gmbh & Co Kg
item VANOUS, ADAM - Iowa State University
item Gardner, Candice

Submitted to: Plant Breeding
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/4/2015
Publication Date: 3/31/2015
Citation: Smelser, A., Blanco, M., Lübberstedt, T., Schechert, A., Vanous, A., Gardner, C.A. 2015. Weighing in on a method to discriminate maize haploid from hybrid seed. Plant Breeding. 134:283-285. DOI: 10.1111/pbr.12260.

Interpretive Summary: Doubled haploid technology is used to develop completely homozygous inbred lines, where each of the chromatids making up a chromosome pair are identical. Its use shortens development time for inbred lines by several years, but it comes with challenges. The inducer line uses a color gene, R-Navajo, or R-nj, as a marker. About 10% of the kernels on a pollinated ear are haploid, and they must be separated from non-haploid kernels. The R-nj system works well when inducing maize germplasm that is yellow or white, with haploid kernels having a colorless embryo and a colored cap. If using exotic germplasm with deep kernel colors, the color conferred by the R-nj gene is not detectable. We tested whether kernel weight could be used to distinguish between haploid kernels and hybrid kernel, using six different genotypes. We found the method to be useful, but each genotype has its own range of kernel weights, and interactions between line (genotype) and kernel type exist. Use of weight as an appropriate sorting method is likely genotype specific.

Technical Abstract: The doubled haploid breeding method can produce maize inbred lines faster than traditional methods, but there are challenges associated with it. Sorting haploid from hybrid seed based on visual color markers is time consuming, and can be difficult due to color inhibitors that obscure pigmentation needed to distinguish between haploid, hybrid, and outcrossed seed. In this study, weight was evaluated as a method to sort haploid from hybrid seed. A first experiment utilized two families for analysis in a preliminary study. Eleven haploid and hybrid kernels from both families were weighed for a total of 44 experimental units. A second experiment was done using six families, using the same format as the previous, for 132 experimental units. Hybrid seed weighed significantly more than haploid seed in both experiments. However, the interaction between line and kernel type was significant in the second experiment. In conclusion, efficacy of sorting haploid from hybrid kernels based on weight depends on the genotypes involved. Keywords: Doubled haploid – Sorting kernels