Tiantao Wang

Calcium (Ca²⁺) is an essential nutrient for plants and enhances their resistance to heavy metal stress. This study employed hydroponic experiments to investigate how varying Ca²⁺ levels (0, 0.5, 2, and 5 mM) regulate maize seedling growth, physiological-biochemical traits, and cellular antioxidant defense systems under cadmium (Cd) stress, thereby alleviating Cd toxicity. The results showed that Ca²⁺ supplementation mitigated the inhibitory effects of Cd stress on root length, dry weight, and photosynthetic pigment content. Additionally, Ca²⁺ application increased the activities of superoxide dismutase (SOD) and catalase (CAT), as well as the contents of glutathione (GSH) and ascorbic acid (ASA) in leaves, with maximum increases of 14.9%, 65.39%, 146%, and 135%, respectively, compared to the control (CK). Under Ca²⁺ treatment, peroxidase (POD) activity significantly decreased, with a maximum reduction of 34.38% compared to CK, while malondialdehyde (MDA) content markedly increased, reaching 19.84% higher than CK. Principal component analysis (PCA) revealed that the 5 mM Ca²⁺ treatment achieved the highest composite score, indicating optimal antioxidant capacity in maize seedlings and reduced membrane lipid peroxidation caused by excessive Cd accumulation. This study enhances the understanding of calcium’s role in plant stress responses and provides insights for safe maize production in Cd-contaminated environments.

The Honghe Hani Rice Terraces System (HHRTS) of Yunnan Province is an important agricultural and cultural heritage landscape. Until now, a large number of local rice landraces have been planted. Mining excellent genes contained in these landraces provides a reference for variety improvement and new variety breeding. In this study, 96 rice landraces collected from the Hani terraces were planted in Honghe Mengzi, Yunnan Province, in 2013, 2014, 2015, and 2021, and five major grain traits were measured and analyzed. The genomic variation of 96 rice landraces was scanned by 201 simple sequence repeat (SSR) markers. The genetic diversity, population structure, and genetic relationships of the natural population were analyzed. The mixed linear model (MLM) method of the TASSEL software was used to analyze the associations between markers and traits. A total of 936 alleles were amplified by 201 pairs of SSR primers. The average number of observed alleles (Na), the effective number of alleles (Ne), Shannon’s information index (I), heterozygosity (H), and the polymorphism information content (PIC) per marker were 4.66, 2.71, 1.08, 0.15, and 0.55, respectively. Ninety-six landraces were divided into two groups by population structure, clustering, and principal component analysis, and indica rice was the main group. The coefficients of variation of the five traits ranged from 6.80 to 15.24%, and their broad heritabilities were more than 70%. In addition, there were positive correlations among the same grain traits between different years. Through MLM analysis, 2, 36, 7, 7, and 4 SSR markers were significantly associated with grain length (GL), grain width (GW), grain thickness (GT), grain length–width ratio (LWR), and thousand-grain weight (TGW), respectively. The explanation rates of phenotypic variation were 16.31 (RM449, Chr. 1)—23.51% (RM316, Chr. 9), 10.84 (RM523, Chr. 3; RM161/RM305, Chr. 5)—43.01% (RM5496, Chr. 1), 11.98 (RM161/RM305, Chr. 5)—24.72% (RM275, Chr. 6), 12.68 (RM126, Chr. 8)—36.96% (RM5496, Chr. 1), and 17.65 (RM4499, Chr. 2)—26.32% (RM25, Chr. 8), respectively. The associated markers were distributed on 12 chromosomes of the genome.