Low-light stress in maize (Zea mays L.): completely opposite cultivar performance under different shading periods

The effects of prolonged low-light stress over the whole growth period and low-light stress at the critical post-silking period on maize yield remain poorly understood, and the differential responses of various cultivars have yet to be systematically compared. To address this, field experiments were conducted in Qitai, Xinjiang, from 2023 to 2024 to investigate the effects of shading period (post-silking shading versus whole-growth-period shading), light intensity levels (CK: natural light; 30: 70% natural light; 50: 50% natural light), and planting densities (7.5 × 10⁴ plants ha^-1 and 12 × 10⁴ plants ha^-1) on two maize cultivars (Xianyu 335, XY335; Zhengdan 958, ZD958). The results showed that when plants were shaded post-silking, insufficient photosynthate supply (source limitation) became the dominant factor leading to yield reduction. In contrast, shading throughout the whole growing period impaired grain sink utilization (sink limitation) and consequently resulted in yield loss. Distinct response patterns to shading at different growth periods were observed between the two cultivars. Under post-silking shading, XY335 had 12.7 and 12.4% higher grain yields than ZD958 under 30 and 50% shading, respectively. By contrast, under whole-growth-period 50% shading, ZD958 produced a 62.7% greater grain yield than XY335. Such different yield responses resulted from differences in source-sink coordination, the ability to remobilize pre-silking reserves, and leaf photosynthetic capacity. Hence, cultivars possessing relevant adaptive traits were prioritized depending on the dominant low-light stress types (short-term seasonal and prolonged low-light). This practice provides a precise guideline for regional maize production under low-light conditions.