Response of florets development and grain formation in different spike wheat cultivars to nitrogen application

Wheat provides 20% of the calorie and protein consumed by humans. Further improvement in wheat yield potential is needed to meet future food demand. As yield is related to the number of grains, an understanding of the generation of grain is critical for increasing yield. Nitrogen is an important nutrient affecting the growth and development of wheat. Wheat yield is calculated as the number of grains per square meter, which in turn is related to the number of fertile florets at anthesis. In this study, the dynamics of floret generation and degeneration were studied in contrasting conditions of 0 kg·hm^-2, 180 kg·hm^-2 and 360 kg·hm^-2 of nitrogen (N). The modern, well-adapted large-spike wheat cultivar 'Zhoumai 16' and multi-spike wheat cultivar 'Yumai 49' were used at the materials. The results indicated that the dynamic characteristics of floret development of two cultivars were similar under different nitrogen applications with increasing degree-days (GDD). The dynamics of floret differentiation conformed to quadratic curve model. Besides, both floret degeneration and infertility conformed to linear equation. Moreover, the correlations were all significant. The large spike-cultivar 'Zhoumai 16' developed more florets than multi-spike cultivar 'Yumai 49', especially under nitrogen level of 180 kg(N)·hm^-2. For increased nitrogen application, large spike cultivar wheat 'Zhoumai 16' had more floret differentiation and faster floret differentiation and degeneration rates, which helped increase kernel number. This clearly indicated that the number of florets was not the only factor that determined grain number, hence there was need to place more focus on cultivation regulation at later stages of floret development. However, multi-spike cultivar 'Yumai 49' had more floret differentiation and fertile spikelet under medium nitrogen level180 kg(N)·hm^-2 than under low and high nitrogen levels. Although the total number of floret differentiation of multi-spike cultivar 'Yumai 49' was less than that of large-spike cultivar 'Zhoumai 16', the degeneration and infertility rates were rather low. Compared with multi-spike cultivar wheat, the 1000-kernel weight of large-spike cultivar was highest for three different nitrogen levels. Under the experimental condition, yield of two cultivars of wheat peaked under 180 kg(N)·hm^-2. It was concluded that 180 kg(N)·hm^-2 increased kernel number of different spike cultivars. However, yield of large-spike cultivar 'Zhoumai 16' improved by increased spike and grain number under high nitrogen rate.