The root system is the only vital organ for plants to connect with soil moisture and nutrients and obtain feedback information. This research aimed to explore the response of different spike type winter wheat varieties to plant and row spacing configurations. Multi-spike and large-spike winter wheat varieties were used as materials. By setting different plant row configurations and planting densities, the spatial and temporal distribution of root length density, root diameter, root dry weight density, and the main control factors of root growth and development of winter wheat during the whole growth period were studied. The results showed that the root system was the most widely distributed and the root diameter was the largest in the 0–40 cm soil depth, with an average root system diameter of more than 0.5 mm. The root length density and root diameter peaked at the heading stage, decreased at the maturity stage, and the root dry weight density peaked at the jointing stage. The jointing stage and heading stage are the most vigorous periods of root growth in winter wheat, when the center of gravity of root growth in winter wheat is gradually moving down. Therefore, the rapid growth and elongation time of a root system can be effectively prolonged at the jointing stage and heading stage, and the root growth rate can be improved. Promoting root thickening can effectively meet the needs for water and nutrients, for the formation and filling of aboveground plants and grains, in the later stage, which is conducive to the formation of aboveground dry matter production and final yield. The root distribution was greatest in the 0–60 cm soil depth, accounting for 95.13–97.84% of the total root length. After the heading stage occurs, the upper roots begin to decline in large quantities. Thus, the jointing stage and heading stage require fertilization and other farmland management operations to increase root nutrients for the ground parts and dry matter accumulation to provide sufficient nutrients so that the number of effective panicles, grain weight, and the number of spike grains coordinate to achieve the highest grain yield. Results showed that the highest yield can be achieved with the planting pattern X2M1. A comprehensive analysis showed that the genetic characteristics of winter wheat varieties were different, and there were some differences in the correlation between wheat yield and root system at the different growth stages. The correlation between the root parameters and yield of multi-spike winter wheat during the overwintering-jointing stage was obvious. For large-spike type winter wheat in the jointing stage, the yield correlation is most obvious.

To understand the molecular mechanism of drought tolerance in sweet sorghum [Sorghum bicolor (L.) Moench], we found the genetic loci associated with single nucleotide polymorphism (SNP) markers and explored drought-tolerance candidate genes. A genome-wide association study (GWAS) of sweet sorghum was performed using the general linear model (GLM), mixed linear model (MLM) and the fixed and random model circulating probability unification (FarmCPU) method in R. Mean productivity (MP), relative drought index (RDI) and stress-tolerance index (STI), based on plant height under two water treatments, were obtained from 354 sweet sorghum accessions from home and abroad. These plant-height drought-tolerance indices showed continuous quantitative variation. Except for the RDI, the others were close to normal distribution. A total of 6186 SNPs were obtained from the resequencing data after quality control and filling. The marker densities on chromosomes 9, 10 and 5 were higher than those on other chromosomes, which were 40.4, 16.5 and 10.0 SNPs within 1 Mb, respectively. The GWAS results showed that 49, 5 and 25 significant SNP loci were detected by the GLM, the MLM and FarmCPU, respectively, many of which were detected by two or more models. Two candidate genes of drought tolerance were annotated: Sb08g019720.1, homologous to the gene encoding the early flowering MYB protein transcription factor in Arabidopsis thaliana; and Sb01g037050.1, homologous to the gene encoding the basic leucine zipper transcription factor in maize. The results of this study can facilitate the cultivar development of drought-tolerant sweet sorghum.