Super hybrid rice improved yield by increasing spikelet amount and efficiency under optimized density-nitrogen cultivation

Abstract

Context

The production pattern of super hybrid rice is high-input, high-yield, and low efficiency. Increasing the number of total spikelets can improve grain yield under combined density-nitrogen cultivation. However, spikelet production efficiency has received less attention, and the association between yield and spikelet production (including amount and efficiency) remains unclear.

Objective

This study evaluated the synergistic mechanism between yield, the number of total spikelets and spikelet production efficiency of super hybrid rice cultivars under combined density-nitrogen conditions.

Methods

Super hybrid rice cultivars were planted under combined density-nitrogen conditions to create various rice populations with different numbers of total spikelets. Path analysis was conducted on yield components. Spikelet characteristics and nutrients dynamics were described during panicle and spikelet development. Spikelet production efficiencies were calculated, and their relationships with the number of total spikelets and yield were evaluated.

Results

The number of total spikelets was the most influential factor in yielding components of super hybrid rice. Among cultivars, super hybrid rice CYQH achieved the highest yield, number of total spikelets, and SPE_N， and it showed the second-best performance for spikelet number per panicle, SPE_DM, and SPE_NSC. Among treatments, the highest yield, number of total spikelets, and SPE_N were realized under the combined density-nitrogen treatment HDHN. The increased number of total spikelets was adjusted by the number of panicles and spikelets per panicle, especially the enhanced secondary branches and spikelets. The dry mass, NSC and nitrogen content increased continuously during panicle and spikelet development, while the C_NSC/N_T decreased first and then increased. Positive correlations existed between yield, the number of total spikelets and spikelet production efficiency. Moreover, there were positive correlations between spikelet number per panicle, secondary branch number, secondary spikelet number and shoot nitrogen content.

Conclusions

This study demonstrated that grain yield, the number of total spikelets and spikelet production efficiency could be synergistically improved in super hybrid rice cultivars. The number of total spikelets was the most influential factor in yield. The improved secondary branches and spikelets increased the spikelets per panicle. The dry mass, NSC, N accumulations and C_NSC/N_T provided nutritional support for panicle and spikelet development. The enhanced spikelet production efficiency suggested a highly coordinated sink-source relationship. The treatment HDHN produced more spikelets to form grain yield, improved nutrient accumulations, and increased the spikelet production efficiency during panicle and spikelet development.

Significance

Optimized density-nitrogen planting benefits the synergistic increase in yield, the number of total spikelets and spikelet production efficiency. This study provides meaningful insights into high-yielding, high-efficiency super hybrid rice production.