Abstract
Despite evidence from previous case studies showing that agronomic traits partially determine the resulting yield of different rice (Oryza sativa L.) varieties, it remains unclear whether this is true at the ecotype level. Here, an extensive dataset of the traits of 7686 rice varieties, released in China from 1978 to 2017, was used to study the relationship between yield and other agronomic traits. We assessed the association between yield and other agronomic traits for four different rice ecotypes, i.e., indica inbred, indica hybrid, japonica inbred, and japonica hybrid. We found that associations between agronomic traits and yield were ecotype-dependent. For both the indica inbred and indica hybrid ecotypes, we found that greater values of certain traits, including the filled grain number per panicle, 1000-grain-weight, plant height, panicle length, grains per panicle, seed setting rate, long growth period, low panicle number per unit area, and low seed length/width ratio, have accounted for high grain yield. In the japonica inbred and japonica hybrid ecotypes, we found that only high panicle number per unit area and long growth period led to high grain yield. Indirectly, growth period consistently had a positive effect on yield in all ecotypes, and plant height had a positive effect on yield for the indicas and japonica inbred only. Plant height had a negative effect for the japonica hybrid. Altogether, our findings potentially have valuable implications for improving the breeds of rice ecotypes.
Highlights
Rice (Oryza sativa L.) is one of the oldest and most important cereal crops—it has been cultivated for 8,200–13,500 years (Molina et al, 2011)
Similar patterns were found for japonica ecotypes, except the 1000-grain-weight. 3http (TGW) and length/width ratio (LW) were lower in the hybrid than inbred ecotype (Figure 1)
We found that the year of release significantly correlated with agronomic traits, especially for per unit area (PN) of indica inbred, panicle length (PL) of indica inbred, filled grain number per panicle (FGN), grains per panicle (GPP), plant height (PH), and grain yield (GY) of all ecotypes (Supplementary Figures S1–S10)
Summary
Rice (Oryza sativa L.) is one of the oldest and most important cereal crops—it has been cultivated for 8,200–13,500 years (Molina et al, 2011). Compared with the average global rice production of 4.3 t ha−1, the average yield of rice in the 30 million ha of China is 6.8 t ha−1. Yield and Yield Components of Rice growing population and urbanization are still major constraints against ensuring food security (Foley et al, 2011; Ray et al, 2012; Qian et al, 2016; Zeng et al, 2017). It is essential to develop high-yielding, climate-resilient and high-quality rice varieties (Venu et al, 2011; Zeng et al, 2017). The development of semi-dwarf varieties through heterosis has substantially increased rice yield in the past 50 years (Xing and Zhang, 2010; Qian et al, 2016). A rational design approach, which is based on extensive accumulated knowledge about the genes that regulate important agronomic traits, has been re-proposed to increase the accuracy and effectiveness of genetic selection for pyramiding multiple desirable traits (Qian et al, 2016; Zeng et al, 2017)
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