Morphological and physiological factors contributing to early vigor in the elite rice cultivar 9,311

Zai Shi,Tian-Gen Chang,Chongrong Wang,Faming Chen,Shao-Chuan Zhou,Baoshan Wang,Mengyao Wang,Xin-Guang Zhu,Zhiwei Zhou,Genyun Chen,Honglong Zhao,Qingfeng Song,Yanjie Wang

doi:10.1038/s41598-020-71913-y

Abstract

Huanghuazhan (HHZ) and 9,311 are two elite rice cultivars in China. They have achieved high yield through quite different mechanisms. One of the major features that gives high yield capacity to 9,311 is its strong early vigor, i.e., faster establishment of its seedling as well as its better growth in its early stages. To understand the mechanistic basis of early vigor in 9,311, as compared to HHZ the cultivar, we have examined, under controlled environmental conditions, different morphological and physiological traits that may contribute to its early vigor. Our results show that the fresh weight of the seeds, at germination, not only determined the seedling biomass at 10 days after germination (DAG), but was also responsible for ~ 80% of variations in plant biomass between the two cultivars even up to 30 DAG. Furthermore, the 9,311 cultivar had a larger root system, which led to its higher nitrogen uptake capacity. Other noteworthy observations about 9,311 being a better cultivar than HHZ are: (i) Ten out of 15 genes involved in nitrogen metabolism were much more highly expressed in its roots; (ii) it had a higher water uptake rate, promoting better root-to-shoot nitrogen transfer; and (iii) consistent with the above, it had higher leaf photosynthetic rate and stomatal conductance. All of the above identified features explain, to a large extent, why the 9,311, as compared to HHZ, exhibits much more vigorous early growth.

Highlights

Huanghuazhan (HHZ) and 9,311 are two elite rice cultivars in China
The differences between the rates of nitrogen uptake of the two cultivars increased over time, which led to 199% and 92% higher NO3- and NH4+ uptake rates at 50 days after germination (DAG) for 9,311, than that for HHZ (Fig. 1d,e)
The 9,311 plants had higher water uptake rate than the HHZ plants, especially from 25 DAG (Fig. 1f), which indicate higher bulk flow of water from the roots to the shoots. These results show that 9,311 has stronger early vigor over HHZ under hydroponic conditions; this includes increases in biomass accumulation, NO3− uptake, NH4+ uptake, as well as water uptake

Summary

Introduction

Huanghuazhan (HHZ) and 9,311 are two elite rice cultivars in China. They have achieved high yield through quite different mechanisms. Vigor, which refers to rapid emergence and early stage growth of plants, is a desirable trait for higher yields in crops, as it enables establishment of quick plant stand as well as its ground cover. These features, in turn, increase canopy photosynthesis and water use e fficiency[17,18,19] Due to these advantages provided to plants, early vigor has long been one of the selection criteria in various crop breeding programs, e.g. those in r ice20, wheat[21] and corn[22]. Using natural variations of grain weight, measured on different panicles, and that too within the same rice cultivar, a positive correlation was observed between the seed weight and the seedling biomass after 14 days after germination (DAG)[26]. There is no consensus regarding what might be the key factor(s) controlling seedling vigor

Objectives

Methods

Results

Conclusion