Heading Uniformity: A New Comprehensive Indicator of Rice Population Quality

Chuanhai Shu,Jian Qin,Yongjian Sun,Zhiyuan Yang,Feijie Li,Mingtian Wang,Dongdong Liu,Na Li,Jun Ma

doi:10.3390/agriculture11080770

Abstract

Productive tiller percentage (PTP) is the only available comprehensive indicator of rice population quality. However, productive panicle number (PN) has a great effect on its characterization accuracy. Panicle exsertion is an important but difficult to describe morphological index; therefore, it cannot be easily determined. The aims of this study were to develop heading uniformity (HU), which describes the difference in the degree of rice panicle exsertion, as a new comprehensive indicator by designing a representative sampling and calculation method and exploring the relationship between HU and yield components. HU first decreased then increased after initial heading, exhibiting a single-valley curve. Adequate HU was obtained by panicle sampling on day two or three (panicle N fertilizer proportion ≤40 or >40%) after initial heading. The explanatory power of PTP for grain yield variance was markedly insufficient in low- and high-PN rice populations. Compared with the percent contribution of PTP to grain yield variance (12.32–41.26%), that of HU (49.02–61.93%) was greater and more stable across rice populations of different PNs. Moreover, HU showed fewer interannual variations, despite large interannual differences in weather and soil conditions. Hence, HU may have applications as a comprehensive indicator of rice population quality.

Highlights

Rice population quality is the basic theory that ensures high rice yields in China
We mainly focused on the following three aspects: (1) determination of the representative heading uniformity (HU) sampling time using a newly proposed HU calculation method; (2) exploration of the internal relationship between HU and grain yield formulation by studying the relationships between HU and panicle number (PN) (SPW); and (3) comparison of HU and Productive tiller percentage (PTP) to verify the ability of HU to characterize rice population quality
The results showed that both PN and single panicle weight (SPW) determined grain yield, but the former had a far lower percent contribution than the latter to grain yield variance; the PN to SPW percent contribution ratio was 8.87 to 37.55%

Summary

Introduction

Rice population quality is the basic theory that ensures high rice yields in China. In this theory, the optimum panicle number (PN) and productive tiller percentages (PTPs) of 70–80% (Indica rice) and 80–90% (Japonica rice) are used as comprehensive indicators of the quality of high-yield rice populations [1,2]. The theory of rice population quality involves seven basic quality indicators, including the total photosynthetic production of rice population during the productive phase, optimum leaf area index (LAI), spikelet number per plant (SN), and grain–leaf ratio [1,6,7]. These indicators can only be used to determine whether a rice population meets the “high-yield” requirements and design specifications, they are all closely related to a PTP-centered comprehensive quality indicator. The uppermost internode elongation reflects the morphological and physiological differences between different tillers, in addition to being sensitive to the external environment

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Methods

Discussion

Conclusion