Agronomy

Plant-parasitic nematodes (PPN) remain one of the major constraints to global agricultural productivity, affecting numerous crops and contributing to substantial yield losses [...]

Heavy metals in livestock and poultry manure cause significant contamination; however, there is currently a lack of scenario analysis research on soil pollution risks under the influence of manure application. This study integrated multiple methods, including multi-source data fusion, heavy metal emission accounting, and ecological risk assessment, to investigate regional soil heavy metal pollution risks under baseline and improved scenarios of manure application, using Hunan Province, China, as a case study. The results indicate that pig manure (49.5%) and cattle manure (47.6%) are the primary sources of heavy metal emissions from livestock and poultry manure. The heavy metal loads on cropland (g/ha) were as follows: Cd (0.51), Hg (0.027), As (0.87), Pb (4.69), Cr (5.38), Cu (93.10), Zn (131.05), and Ni (5.07). Among the eight heavy metals, Cd poses the most prominent soil pollution risk. Under the baseline scenario (100% manure application), the study area exhibited an overall moderate ecological hazard level after 37 years of continuous application, with 71.93% of the cropland classified as Risk Level II and 7.04% as Risk Level III. After 184 years, a strong ecological hazard level was reached, with 54.93% of the cropland classified as Risk Level III and 19.64% as Risk Level IV. Under improved scenarios (75%, 50%, and 25% manure application), the overall moderate ecological hazard level was reached after 49, 74, and 147 years of continuous application, respectively. This study provides a theoretical and methodological basis for regional soil heavy metal pollution control and source analysis.

Low temperature exerts severe adverse effects on maize growth, particularly during the seedling stage. Screening for cold-tolerant maize genotypes is highly significant for identifying genes associated with cold tolerance and enhancing maize performance under low, suboptimal temperature conditions. The identification of representative cold tolerance-related genes is of great significance for the breeding of cold-resistant maize varieties. In this study, a diversity panel of 205 materials was evaluated and classified for cold tolerance at the seedling stage. The coefficients of variation of all materials ranged from 14.53% to 35.71%, reflecting considerable genetic diversity within the panel. The correlation coefficients for each phenotypic trait between the cold-treated (CT) and control (CK) maize materials ranged from 0.60 to 0.90, further indicating that all traits displayed varying degrees of sensitivity to cold stress. A comprehensive evaluation of cold tolerance using the D value was conducted. The D values of all materials ranged from 0.355 to 0.863, with a mean value of 0.64. A hierarchical clustering analysis was performed to classify all materials into five categories based on their cold tolerance. Further, 17 SNPs were identified using GWAS analysis, and 12 candidate genes were located within the regions related to the SNPs. Some candidate genes were closely associated with cold tolerance, such as genes encoding MYB and GRAS transcription factors, leucine-rich repeat (LRR) proteins, and protein kinases. Validation by qRT-PCR confirmed that the expression of some genes was induced under cold stress conditions. These findings lay a crucial foundation for breeding cold-tolerant maize varieties and for further exploration of genes associated with cold tolerance.