Excessive planting density and heavy rainfall weather threatens global agriculture, particularly affecting maize. Biochar is an environmentally friendly soil amendment that has a yield-increasing effect. However, the regulatory mechanism of biochar frequency on crop internode development and photosystem II photosynthetic efficiency remains unknown. A total of nine treatments were followed in this experiment. Three applications of biochar were as follows: no biochar application (B0); biochar application at 4.2 t ha⁻¹ year⁻¹ (B1); and biochar application at 8.4 t ha⁻¹ 2 year⁻¹ (B2), alongside three nitrogen (N) fertilizer rates (0, N0; 180 kg ha⁻¹, N1 and 225 kg ha⁻¹, N2). The results showed that the internode thickness of the 2nd to 5th nodes under N2B2 treatment increased by 17.7%, 16.0%, 19.7%, and 21.7%, respectively, compared to N0B0. Annual biochar application had a higher stem diameter coefficient for the 1st to 3rd nodes than no biochar (B0) and treatments applied every two years (B2). Annual biochar application had the highest dry weight of internodes and plant height compared with B0 and B2. The relative chlorophyll content of leaves was significantly increased by biochar combined with N fertilizer or by N fertilizer alone. Biochar combined with N fertilizer significantly reduced NPQt and ΦNPQ, which were reduced by 59% and 50%, respectively, under N2B1 treatment compared with N0B0. The N2B1 treatment increased ΦII by 30% compared to N0B0. Stem diameter coefficient was significantly negatively correlated with NPQt and ΦNPQ and significantly positively correlated with ΦII and Fv/Fm. Compared to B1, B2 increased the maize yield. Annual biochar application combined with N fertilizer reduced stem collapse and enhanced post-flowering photosynthesis. Overall, considering the yield traits, 8.4 t ha⁻¹ biochar application combined with 180 kg ha⁻¹ N fertilizer treatment was the best. This study will provide reference data for cultivation regulation to enhance maize’s resistance to collapse and maintain photosynthetic capacity.

Background/Objectives: Popcorn (Zea mays L. var. everta) is an important specialty maize type; however, the genetic variation underlying popping-related quality traits remains insufficiently characterized in breeding. Methods: In this study, 18 popcorn inbred lines were analyzed using 25 simple sequence repeat (SSR) markers distributed across all 10 maize chromosomes, and 16 lines were further evaluated for popping performance and image-based flake morphology. Results: Substantial phenotypic variation was observed among the tested lines, with expansion volume ranging from 173.33 to 343.33 mL and expandability ranging from 16.79- to 32.46-fold. Image-based analysis of 957 popped kernels revealed continuous variation in flake circularity, indicating that flake morphology represents a quantitative trait rather than a strictly discrete classification. SSR analysis detected 2 to 11 alleles per locus, with polymorphism information content values ranging from 0.05 to 0.85, indicating moderate-to-high genetic diversity among the tested lines. Principal component analysis (PCA), unweighted pair group method with arithmetic mean (UPGMA) clustering, and population structure analysis revealed clear genetic differentiation and heterogeneous genetic backgrounds within the germplasm collection. Marker–trait association analysis identified several putative SSR loci associated with expansion efficiency, flake morphology, pericarp retention, and popping dynamics. Notably, marker M18 was putatively associated with both expansion volume and expandability. Conclusions: Based on these results, a conceptual framework was proposed in which popping-related traits were organized into partially independent but interconnected functional modules. Overall, this study provides SSR-based genetic information for popcorn germplasm characterization and offers preliminary marker resources for quality-oriented popcorn breeding.

Seed germination is a critical determinant of seedling establishment, stress resistance, and final yield. ABA catabolism plays a central role in releasing seed dormancy and promoting germination, and ABA8ox is the key rate-limiting enzyme in this process. In this study, we used wild-type maize B73, and ZmABA8ox1b CRISPR-Cas9 knockout mutant as materials to investigate the biological function of ZmABA8ox1b. Compared with the wild type, the zmaba8ox1b mutant significantly delayed seed germination and enhanced the sensitivity to exogenous ABA. Endogenous ABA content in mutant embryos was drastically increased, indicating that ZmABA8ox1b is essential for ABA degradation during germination. The loss of ZmABA8ox1b function led to the activation of the ABA signaling pathway and severely impaired the responsiveness to exogenous ABA. Moreover, the mutation disturbed the expression and ABA responsiveness of auxin, gibberellin, ethylene, jasmonic acid, and brassinosteroid pathways, leading to a hormonal network imbalance. In conclusion, ZmABA8ox1b positively regulates maize seed germination by coordinating ABA catabolism and multi-hormone signal crosstalk. This study preliminarily clarifies the molecular mechanism of ZmABA8ox1b in germination control and provides important gene resources and theoretical support for breeding maize varieties.