Kernel water content (KWC) and kernel dehydration rate (KDR) are two main factors affecting maize seed quality and have a decisive influence on the mechanical harvest. It is of great importance to map and mine candidate genes related to KWCs and KDRs before physiological maturity in maize. 120 double-haploid (DH) lines constructed from Si287 with low KWC and JiA512 with high KWC were used as the mapping population. KWCs were measured every 5 days from 10 to 40 days after pollination, and KDRs were calculated. A total of 1702 SNP markers were used to construct a linkage map, with a total length of 1,309.02 cM and an average map distance of 0.77 cM. 10 quantitative trait loci (QTLs) and 27 quantitative trait nucleotides (QTNs) were detected by genome-wide composite interval mapping (GCIM) and multi-locus random-SNP-effect mixed linear model (mrMLM), respectively. One and two QTL hotspot regions were found on Chromosome 3 and 7, respectively. Analysis of the Gene Ontology showed that 2 GO terms of biological processes (BP) were significantly enriched (P ≤ 0.05) and 6 candidate genes were obtained. This study provides theoretical support for marker-assisted breeding of mechanical harvest variety in maize.

Seed is the chip of agriculture and the upgrading of excellent varieties has played an important role in improving the yield of corn in China. It is of great practical significance to study the historical contribution and developing trend of mega maize varieties in China in recent 40 years. Based on the dataset of planting area of individual maize varieties released by the National Extension and Service Center of Agricultural Technology from 1982 to 2020, 27 mega maize varieties such as Zhengdan 958 in recent 40 years with the total promotion of 321 million hectares accounting for 29.09% of the total corn planting area in China were screened..There were four utmost mega varieties (Zhengdan 958, Zhongdan 2, Danyu 13, and Xianyu 335) and six massive mega varieties (Jundan 20, Yedan 2, Nongda 108, Yedan 13, Sidan 19, and Yandan 14). The promotion period was 8-30 years, with an average of 17.63 years, the maximum promotion area in a single year was 699,700-4,569,500 hm2, with an average of 1,507,900 hm2. It was mainly distributed in Shandong, Henan, Hebei, Jilin, Heilongjiang, Inner Mongolia, and other production regions and the provinces (regions) with 13 varieties exceeding 666,700 hm2 per year were Shandong, Henan, Hebei, Jilin, Heilongjiang, Inner Mongolia, Liaoning, and Sichuan. The proportion of planting area of mega varieties to the total area increased rapidly from 1982 to 1989, remained stable from 1990 to 1997, decreased after 1998, and decreased to about 12% by 2020. Some varieties such as Yufeng 303 and Zhongkeyu 505 had the potential to develop into mega varieties. In the future, intelligent design breeding will efficiently cultivate a new generation of breakthrough varieties and accelerate the improvement of maize yield. According to the current maize production problems and future development trends, it is recommended to further improve the regional test of maize varieties in terms of distribution layout, test accuracy and variety approval standards of regional tests.

Leaf width is a key determinant of planting density and photosynthetic efficiency. In an effort to determine which genes regulate maize plant leaf width, we performed a genome-wide association study (GWAS) of 1.49 × 106 single nucleotide polymorphisms (SNPs) in 80 sequenced backbone inbred maize lines in Jilin Province, China, based upon phenotypic leaf width data from two years. In total, 14 SNPs were identified as being significantly related to leaf width (p < 0.000001), with these SNPs being located on chromosomes 1, 2, 3, 5, 6, 7, 8, and 9. A total of five candidate genes were identified within a mean linkage disequilibrium (LD) distance of 9.7 kb, with a significant SNP being identified within the Zm00001d044327 candidate gene. RNA was then isolated from 12 different inbred maize lines from this GWAS study cohort and was used to conduct qPCR analyses which revealed significant differences in Zm00001d044327 expression among strains exhibiting significant differences in leaf width. Based on an assessment of EMS mutant lines harboring a conserved amino acid stop mutation and two non-synonymous mutations in Zm00001d044327 that exhibited a narrow leaf width, these data suggested that Zm00001d044327 is a key regulator of maize leaf width.