Background and aims As drought threatens the yield and quality of maize (Zea mays L.), it is important to dissect the molecular basis of maize drought tolerance. Flavonoids, participate in the scavenging of oxygen free radicals and alleviate stress-induced oxidative damages. This study aims to dissect the function of flavonoids in the improvement of maize drought tolerance. Methods Using far-infrared imaging screening, we previously isolated a drought overly insensitivity (doi) mutant from an ethyl methanesulfonate (EMS)-mutagenized maize library and designated it as doi57. In this study, we performed a physiological characterization and transcriptome profiling of doi57 in comparison to corresponding wild-type B73 under drought stress. Results Under drought stress, doi57 seedlings displayed lower leaf-surface temperature (LST), faster water loss, and better performance in growth than B73. Transcriptome analysis reveals that key genes involved in flavonoid biosynthesis are enriched among differentially expressed genes in doi57. In line with these results, more flavonols and less hydrogen peroxide (H2O2) were accumulated in guard cells of doi57 than in those of B73 with the decrease of soil water content (SWC). Moreover, the capacity determined from doi57 seedling extracts to scavenge oxygen free radicals was more effective than that of B73 under the drought treatment. Additionally, doi57 seedlings had higher photosynthetic rates, stomatal conductance, transpiration rates, and water use efficiency than B73 exposed to drought stress, resulting in high biomass and greater root/shoot ratios in doi57 mutant plants. Conclusion Flavonoids may facilitate maize seedling drought tolerance by lowering drought-induced oxidative damage as well regulating stomatal movement.

Water shortage is a global challenge and affects crop growth and development seriously. Stoma is the main channel of plant water transpiration. Water transpiration through stomata is an endothermic process and affects temperature of plants, especially leaf surface. In this study, we established a method for screening maize seedling mutant with abnormal leaf temperature by far infrared imaging. We found that seedling mutants with abnormal leaf temperature manifested different drought tolerance. Mutants with lower leaf temperature demonstrated faster moisture loss rate, poorer drought tolerance, higher osmotic potential, lower leaf relative water content, more accumulation of hydrogen peroxide, more serious cell membrane damage and more robust root systems and biomass under drought treatment, which are opposite in maize seedling mutants with higher leaf surface temperature compared with the corresponding control. Taken together, the method we established is an effective way to screen maize mutants with abnormal drought response.

Grain protein content (GPC) is an important nutritional quality trait of wheat. Aegilops tauschii Coss. is a progenitor of common wheat and has been shown to have high GPC. The objective of this study was to identify quantitative trait loci (QTL) for GPC using A. tauschii–Triticum aestivum L. recombinant lines. An advanced BC2F6 population (112 lines) containing A. tauschii segments was developed using synthetic octaploid wheat (hexaploid wheat Zhoumai 18 × A. tauschii T093), which displayed significant phenotype variances. Two quality traits, GPC and wet gluten, and four yield-related traits, thousand kernel weight, spikelet number per plant, grain number per spike, and grain weight per spike, were evaluated. The results show that the mean GPCs of these lines were significantly higher than those of Zhoumai 18. Correlation and mapping analyses indicated that quality traits were weakly negatively correlated with yield traits. Furthermore, 16 A. tauschii-derived QTL for GPC were detected in the recombinant inbred lines, and four stable QTL that have no significant negative effects on yield and are located within the same marker interval were detected in both environments. Additionally, high-protein, high-yield lines 150228 and 150368 with stable QTL were obtained, and both can be directly utilised for fine mapping of the GPC genes and molecular marker–assisted selection to achieve synergistic improvement of wheat yield and protein content.