RESUMO
Durum wheat grains (Triticum turgidum L. ssp. durum) are the main source for the production of pasta, bread and a variety of products consumed worldwide. The quality of pasta is mainly defined by the rheological properties of gluten, an elastic network in wheat endosperms formed of gliadins and glutenins. In this study, the allelic variation at five glutenin loci was analysed in 196 durum wheat genotypes. Two loci (Glu-A1 and Glu-B1), encoding for high-molecular-weight glutenin subunits (HMW-GS), and three loci (Glu-B2, Glu-A3 and Glu-B3), encoding for low molecular weight glutenin subunits (LMW-GS), were assessed by SDS-PAGE. The SDS-sedimentation test was used and the grain protein content was evaluated. A total of 32 glutenin subunits and 41 glutenin haplotypes were identified. Four novel alleles were detected. Fifteen haplotypes represented 85.7% of glutenin loci variability. Some haplotypes carrying the 7 + 15 and 7 + 22 banding patterns at Glu-B1 showed a high gluten strength similar to those that carried the 7 + 8 or 6 + 8 alleles. A decreasing trend in grain protein content was observed over the last 85 years. Allelic frequencies at the three main loci (Glu-B1, Glu-A3 and Glu-B3) changed over the 1915-2020 period. Gluten strength increased from 1970 to 2020 coinciding with the allelic changes observed. These results offer valuable information for glutenin haplotype-based selection for use in breeding programs.
RESUMO
The grain protein content (GPC) in rice is low, and more efforts with agronomic and molecular approaches were performed to increase them. However, the rice research focusing on the plant physiological behaviour that modulates the phenomenon of grain protein filling is very scarce. This work contains physiological parameters related to photosynthetic activity in the flag leaf in the grain filling period and N partitioning assays of high (Nutriar) and traditional (Camba) GPC cultivars. Results indicated a higher photosynthetic capacity, a better capacity to provide CO2 to the chloroplast and a healthier PSII structure in Camba relative to Nutriar. Chlorophyll fluorescence parameters decreased more steeply over time in the high protein variety, and a strong negative correlation was observed between GPC and PSII structure parameters. N content in the flag leaf at anthesis showed lower values and higher remobilisation during the grain filling period in Nutriar compared to Camba. The results of this work suggested that the inactivation of some PSII structures in higher GPC cultivars is associated with N remobilisation and would contribute to an increase in the free N available to be translocated to the grain.