Limitation of Unloading in the Developing Grains Is a Possible Cause Responsible for Low Stem Non-structural Carbohydrate Translocation and Poor Grain Yield Formation in Rice through Verification of Recombinant Inbred Lines.

Guohui Li,Shaobing Peng,Kehui Cui,Lixiao Nie,Musong Yuan,Junfeng Pan,Jianliang Huang,Wencheng Wang,Pravat K Mohapatra,Qiuqian Hu

doi:10.3389/fpls.2017.01369

Abstract

Remobilisation of non-structural carbohydrates (NSC) from leaves and stems and unloading into developing grains are essential for yield formation of rice. In present study, three recombinant inbred lines of rice, R91, R156 and R201 have been tested for source-flow-sink related attributes determining the nature of NSC accumulation and translocation at two nitrogen levels in the field. Compared to R91 and R156, R201 had lower grain filling percentage, harvest index, and grain yield. Meanwhile, R201 had significantly lower stem NSC translocation during grain filling stage. Grain filling percentage, harvest index, and grain yield showed the consistent trend with stem NSC translocation among the three lines. In comparison with R91 and R156, R201 had similarity in leaf area index, specific leaf weight, stem NSC concentration at heading, biomass, panicles m-2, spikelets per panicle, remobilization capability of assimilation in stems, sink capacity, sink activity, number and cross sectional area of small vascular bundles, greater number and cross sectional area of large vascular bundles, and higher SPAD, suggesting that source, flow, and sink were not the limiting factors for low stem NSC translocation and grain filling percentage of R201. However, R201 had significant higher stem and rachis NSC concentrations at maturity, which implied that unloading in the developing grains might result in low NSC translocation in R201. The results indicate that stem NSC translocation could be beneficial for enhancement of grain yield potential, and poor unloading into caryopsis may be the possible cause of low stem NSC translocation, poor grain filling and yield formation in R201.

Highlights

Rice is one of the most important food crops for mankind
Compared to R91 and R156, R201 had similar biomass, panicles m−2, spikelets per panicle and sink capacity under low nitrogen application (LN) and high nitrogen application (HN), but grain yield and harvest index of R201 was lower on account of poor grain filling under LN and HN (Table 1), and nearly half of the grains in R201 remained un-filled or poorly filled
HN improved grain filling percentage of R201 resulting in increased HI and grain yield, it could not reach the level of the other two lines

Summary

Introduction

Substantial growth of rice consumers, especially in Asia, has increased the demand for overall grain production. During the vegetative and early reproductive stages, carbon assimilates are temporarily stored in stems and leaf sheaths of cereals as non-structural carbohydrates (NSC) that move to the developing grains at the maturation phase (Scofield et al, 2009). Enhancing translocation of stem NSC to developing grains is beneficial for grain yield formation. NSC reserves in the remaining stem have vital contribution to the speed of vegetative re-growth, flowering, and grain-filling of the second crop (Slewinski, 2012). Wang et al (2016) found that stem reserves are most critical for grain yield formation of short-duration rice varieties, suggesting that pre-heading stem NSC should be considered for breeding early maturing rice. Increasing the pre-anthesis NSC accumulation and the post-anthesis NSC translocation to grains is one of the approaches to improve grain yield of rice

Methods

Results

Conclusion