Seed vigor, an important index of seed quality, determines the potential for rapid and uniform emergence of plants. The objective of this study was to explore a rapid method for evaluating seed vigor. To analyze the correlation of seed traits and seedling traits related to seed vigor, we designed five experiments including nitrogen fertilizer, irrigation and seed sorting treatments in wheat. The results showed that only the absolute content of protein (ACP) in wheat seed was significantly correlated with plant dry weight in five experiments. Subsequently, another experiment including 30 wheat seed lots was used to validate the above results. Although 100-grain weight was also correlated with plant dry weight (R = 0.799, p < 0.01), the correlation coefficient was lower than that between ACP in seed and plant dry weight (R = 0.897, p < 0.01). Moreover, the results of three experiments using maize seeds was similar with above. The relative content of protein in seed detected by near-infrared spectrum combining with seed weight could realize rapid and nondestructive testing ACP in seed. Collectively, ACP in crop seed could be applied in rapid evaluation of seed vigor and could potentially be used for processing and screening high vigor seeds.

Water uptake is the fundamental requirement for the initiation and completion of seed germination that is a vital phase in the life cycle of seed plants. We found that seeds produced under four nitrogen levels showed significantly different germination speed. The objective of this study was to study the mechanism of rapid seed germination and explore which pathways and genes play critical roles in radicle protrusion. Anatomical data revealed that seed protein content affected endosperm structure of seeds. Moreover, scanning electron microscope maps showed that faster germinated seeds had a looser endosperm structure compared with other seeds. Subsequently, high throughout RNA-seq data were used to compare the transcriptomes of imbibed seeds with different germination speed. Gene ontology (GO) term enrichment analysis revealed that cell wall metabolism related genes significantly up-regulated in faster germinated seeds. In these genes, the top four were chitinase that had about fourfold higher expression in faster germinated seeds. Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis showed that faster germinated seeds had enhanced expression in glutathione metabolism. By combining these results, we propose a model for nitrogen fertilizer affects germination speed of wheat seed, which provide new insights into seed germination.

Nitrogen fertilizer is a critical determinant of grain yield and seed quality in wheat. However, the mechanism of nitrogen level during seed production affecting wheat seed vigor and seedling establishment at the transcriptome level remains unknown. Here, we report that wheat seeds produced under different nitrogen levels (N0, N168, N240, and N300) showed significant differences in seed vigor and seedling establishment. In grain yield and seed vigor, N0 and N240 treatments showed the minimum and maximum, respectively. Subsequently, we used RNA-seq to analyze the transcriptomes of seeds and seedlings under N0 and N240 at the early stage of seedling establishment. Gene Ontology (GO) term enrichment analysis revealed that dioxygenase-activity-related genes were dramatically upregulated in faster growing seedlings. Among these genes, the top three involved linoleate 9S-lipoxygenase (Traes_2DL_D4BCDAA76, Traes_2DL_CE85DC5C0, and Traes_2DL_B5B62EE11). Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis revealed that pathways involved in nutrient mobilization and the antioxidant system showed enhanced expression under N240. Moreover, seeds with faster growing seedlings had a higher gene expression level of α-amylase, which was consistent with α-amylase activity. Taken together, we propose a model for seedling establishment and seed vigor in response to nitrogen level during seed production.

Glyphosate (GP)-based herbicides have been widely applied to crops for weed control and pre-harvest desiccation. The objective of this research was to evaluate the effects of pre-harvest GP application on maize or how it physiologically alters this crop. Here, we applied four GP treatment (Control, GP150, GP200, and GP250) on maize lines of Z58 and PH6WC belonging to different maturity groups at grain-filling stages form DAP30 to DAP45. GP application significantly decreased the grain moisture content at harvest by 22–35% for Z58 and by 15–41% for PH6WC. However, the responses of grain weight to glyphosate vary with inbred lines and application time. A high concentration of glyphosate (GP250) reduced the grain weight of Z58 and low concentrations (GP150 and GP200) did not affect, while the grain weight of PH6WC significantly decreased under glyphosate treatment. In summary, our results revealed that timely and appropriate GP application lowers grain moisture content without causing seed yield and quality loss. GP application adversely affected photosynthesis by promoting maturation and leaf senescence. Meanwhile, it also enhanced non-structural carbohydrate (soluble sugars and starch) remobilization from the vegetative organs to the grains. Hence, GP treatment coordinates plant senescence and assimilate remobilization. RNA sequencing revealed that glyphosate regulated the transcript levels of sugar signaling-related genes and induced assimilate repartitioning in grains. This work indicates the practical significance of GP application for maize seed production and harvest, which highlights the contributions of source-sink communication to maize yield in response to external stress or pre-harvest desiccant application.

Background The stalk rind is one of the important factors affecting maize stalk strength that is closely related to stalk lodging. However, the mechanism of rind development in maize is still largely unknown. Results In this study, we analyzed the mechanical, anatomical, and biochemical properties of the third basal internode in one maize non-stiff-stalk (NSS) line and two stiff-stalk (SS) lines. Compared with the NSS line, the two SS lines had a significantly higher rind penetrometer resistance, thicker rind, and higher dry matter, hemicellulose, cellulose, and lignin weights per unit length. RNA-seq analysis was used to compare transcriptomes of the third basal internode of the two SS lines and the NSS line at the ninth leaf and tasseling stages. Gene Ontology (GO) enrichment analysis revealed that genes involved in hydrolase activity (hydrolyzing O-glycosyl compounds) and cytoskeleton organization were significantly up-regulated in the two SS lines at the ninth leaf stage and that microtubule process-related genes were significantly up-regulated in the two SS lines at the tasseling stage. Moreover, the two SS lines had enhanced expression of cell wall metabolism-related genes at the tasseling stage. Conclusions The synthesis of cell wall polysaccharides and the cytoskeleton might play important roles in internode development. Our results can be applied for screening lodging-resistant inbred lines and breeding lodging-resistant cultivars in maize.