Drought stress induced pollen sterility is a detrimental factor reducing grain number in wheat. Exploring the mechanisms underlying pollen fertility under drought conditions could assist breeding high-yielding wheat cultivars with stress tolerance. Here, by using two Chinese wheat cultivars subjected to different levels of polyethylene glycol (PEG)-induced drought stress, possible links between pollen fertility and stress tolerance were analyzed under different levels of drought stress at the young microspore stage. In both cultivars, higher grain number reduction was observed under condition of lower water availability. Overall, the drought tolerant cultivar (Jinmai47) exhibited less grain number reduction than the drought sensitive cultivar (Shiluan02-1) under all stress conditions. Compared with Shiluan02-1, Jinmai47 exhibited superior physiological performance in terms of leaf photosynthetic rate, ear carbohydrate accumulation, pollen sink strength, pollen development and fertility under stress. Moreover, Jinmai47 showed a lower increase in endogenous abscisic acid in ears than Shiluan02-1. Furthermore, higher levels of superoxide dismutase (SOD) and peroxidase (POD) activities were also found in the drought tolerant cultivar Jinmai47 under PEG stress, compared with the drought sensitive cultivar Shiluan02-1. Changes in these physiological traits could contribute to better pollen development and male fertility, ultimately leading to the maintenance of grain number under drought stress.

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Climate change causes shading and threatens wheat (Triticum aestivum L.) yield. Understanding the effects of shading on grain number and morphological characteristics of winter wheat during the young microspore (YM) stage may secure grain yield. Field and pot experiments were performed with six widely planted winter wheat cultivars in the North China Plain (NCP), subjected to 98% blocking of natural light for different shading durations (0, 1, 2, 3, 4, 5, and 6 d) during the YM stage. Results showed that the YM stage was highly sensitive to shading stress, which significantly reduced grain number, causing grain yield loss. Moreover, response to shading varied among cultivars. Sensitive cultivars, such as Kenong9204 and Liangxing99, showed decreases in grain yield per plant of 32.2 to 74.9% and 25.7 to 91.4% in 2016 and 23.0 to 89.2% and 21.9 to 94.3% in 2017 with increasing shading duration. Reduction in grain yield with increasing shading duration was associated with decreasing grain number, grain weight, plant height, and dry matter weight of main stems and tillers. Tolerant cultivars Jimai32 and Henong825 experienced decreases in grain yield per plant of 8.2 to 17.3% and 11.3 to 14.2% in 2016 and 9.7 to 23.7% and 6.5 to 18.5% in 2017 with increasing shading duration. Adaptation of tolerant cultivars to shading was enhanced by rapid tiller development and photosynthesis recovery, inducing productive tillers to increase grain number per tiller, thus resulting in a smaller reduction in grain yield. Therefore, selecting shade‐tolerant cultivars may help to ensure high yield in winter wheat in fog‐haze areas of the NCP.

With increasing water shortage resources and extravagant nitrogen application, there is an urgent need to optimize irrigation regimes and nitrogen management for winter wheat (Triticum aestivum L.) in the North China Plain (NCP). A 4-year field experiment was conducted to evaluate the effect of three irrigation levels (W1, irrigation once at jointing stage; W2, irrigation once at jointing and once at heading stage; W3, irrigation once at jointing, once at heading, and once at filling stage; 60 mm each irrigation) and four N fertilizer rates (N0, 0; N1, 100 kg N ha −1 ; N2, 200 kg N ha −1 ; N3, 300 kg N ha −1 ) on wheat yield, water use efficiency, fertilizer agronomic efficiency, and economic benefits. The results showed that wheat yield under W2 condition was similar to that under W3, and greater than that under W1 at the same nitrogen level. Yield with the N1 treatment was higher than that with the N0 treatment, but not significantly different from that obtained with the N2 and N3 treatments. The W2N1 treatment resulted in the highest water use and fertilizer agronomic efficiencies. Compared with local traditional practice (W3N3), the net income and output-input ratio of W2N1 were greater by 12.3 and 19.5%, respectively. These findings suggest that two irrigation events of 60 mm each coupled with application of 100 kg N ha -1 is sufficient to provide a high wheat yield during drought growing seasons in the NCP.