Single nucleotide polymorphisms (SNPs) are abundantly and evenly distributed throughout the genomes of most plant species. These markers have become popular for use in genetic research in many crops. SNP markers can be used to screen maize cultivars rapidly during the early growth stages. In this study, to develop additional SNP markers for maize, we chose 20 SNP sites per chromosome from the maizeGDB website (www.maizegdb.org) and designed primers with two base pair mismatches using Primer Designer 4 based on putative SNP sites of the B73 genome sequence. The polymerase chain reaction (PCR) products ranged from 200 to 500 bp in size, whereas no PCR product was detected when the SNP site was present in Korean waxy corn. Using nine Korean commercial F₁ hybrids of waxy corn, including Chalok 1, Chalok 4, Ilmichal, Eolrukchal 1, Heukjinjuchal, Hayanchal 95, Mibaekchal, Mibaek 2, and Miheukchal, we selected 16 primer sets showing clear bands or no bands. Based on cluster analysis, we confirmed that the nine Korean waxy corn hybrids could clearly be distinguished. The SNP marker sets are easy to utilize through simple PCR and agarose gel electrophoresis. These results suggest that analysis using the SNP marker set designed in this study would be faster, cheaper, and more reproducible than that using other genotyping tools, such as cleaved amplified polymorphic sequence markers, which require the use of restriction enzymes.

Most Bt transgenic rice events have an underlying grain cost depending on the insect pressure in the field. This study was conducted (1) to determine if the cry1Ac/bar genetically modified (GM) rice (designated Agb0101) based on a Korean japonica rice cultivar has any underlying grain cost and (2) to develop cry1Ac/bar GM rice lines with yield performance similar to those of Korean elite cultivars via crossbreeding. A three-year field experiment showed that Agb0101 had a high underlying grain cost equivalent to 18% grain yield loss, and this cost was mainly due to the grain number per panicle. Moreover, it was found that the cry1Ac/bar transgene was inherited as a single dominant gene. BC₁F₄―F₅ crossbred progeny derived from an anther culture of Agb0101―showed phenotypic resemblance to non-transgenic Korean elite cultivars, resulting in a decrease in the grain yield cost of Agb0101 from 27% to 10%. These results suggest that Bt-GM rice-oriented cross-fertilization with a non-GM elite cultivar followed by two- or threefold selection is a feasible method to minimize or remove the underlying grain cost of the Bt transgenic insect-resistant rice line.