Marker-assisted pyramiding of γ-tocopherol methyltransferase and glutamate formiminotransferase genes for development of biofortified sweet corn hybrids.

Micronutrients, including vitamins, minerals, and other bioactive compounds, have tremendous impacts on human health. Much progress has been made in improving the micronutrient content of inbred lines in various crops through biofortified breeding. However, biofortified breeding still falls short for the rapid generation of high-yielding hybrids rich in multiple micronutrients. Here, we bred multi-biofortified sweet corn hybrids efficiently through marker-assisted selection. Screening by molecular markers for vitamin E and folic acid, we obtained 15 inbred lines carrying favorable alleles (six for vitamin E, nine for folic acid, and three for both). Multiple biofortified corn hybrids were developed through crossing and genetic diversity analysis.

Structural parameters for X-ray micro-computed tomography (µCT) and their relationship with the breakage rate of maize varieties.

BACKGROUND: High grain breakage rate is the main limiting factor encountered in the mechanical harvest of maize grain. X-ray micro-computed tomography (µCT) scanning technology could be used to obtain the three-dimensional structure of maize grain. Currently, the effect of maize grain structure on the grain breakage rate, determined using X-ray µCT scanning technology, has not been reported. Therefore, the objectives of this study are: (i) to obtain the shape, geometry, and structural parameters related to the breakage rate using X-ray µCT scanning technology; (ii) to explore relationships between these parameters and grain breakage rate. RESULT: In this study, 28 parameters were determined using X-ray µCT scanning technology. The maize breakage rate was mainly influenced by the grain specific surface area, subcutaneous cavity volume, sphericity, and density. In particular, the breakage rate was directly affected by the subcutaneous cavity volume and density. The maize variety with high density and low subcutaneous cavity volume had a low breakage rate. The specific surface area (r = 0.758*), embryo specific surface area (r = 0.927**), subcutaneous cavity volume ratio (0.581*), and subcutaneous cavity volume (0.589*) of maize grain significantly and positively correlated with breakage rate. The cavity specific surface area (- 0.628*) and grain density (- 0.934**) of maize grain significantly and negatively correlated with grain breakage rates. Grain shape (length, width, thickness, and aspect ratio) positively correlated with grain breakage rate but the correlation did not reach statistical significance. The susceptibility of grain breakage increased when kernel weight decreased (- 0.371), but the effect was not significant. CONCLUSIONS: The results indicate that X-ray µCT scanning technology could be effectively used to evaluate maize grain breakage rate. X-ray µCT scanning technology provided a more precise and comprehensive acquisition method to evaluate the shape, geometry, and structure of maize grain. Thus, data gained by X-ray µCT can be used as a guideline for breeding resistant breakage maize varieties. Grain density and subcutaneous cavity volume are two of the most important factors affecting grain breakage rate. Grain density, in particular, plays a vital role in grain breakage and this parameter can be used to predict the breakage rate of maize varieties.