Relationships of non-structural carbohydrates accumulation and translocation with yield formation in rice recombinant inbred lines under two nitrogen levels

Stem non-structural carbohydrates (NSCs) and its relationship with yield formation was investigated under low nitrogen (LN) and normal nitrogen (NN) treatments, using 46 recombinant inbred lines from Zhenshan 97 x Minghui 63 (Oryza sativa). Apparent contribution of transferred NSC to grain yield (AC(NSC)) ranged from approximately 1 to 28% under LN and from 1 to 15% under NN. Concentration and total mass of NSC in stem (TMNSC) at heading, apparent transferred mass of NSC (ATM(NSC)) and AC(NSC) were larger under LN compared with NN. However, there was no significant difference in the apparent ratio of transferred NSC from stems to grain (AR(NSC)). ATM(NSC) was positively correlated with grain yield, 1000-grain weight and AC(NSC) under both nitrogen levels, whereas AR(NSC) was highly correlated with harvest index and AC(NSC). Leaf area contributed more strongly to grain yield compared with ATM(NSC) under both LN and NN. ATM(NSC) showed larger direct effects on grain yield under LN compared with NN. TMNSC at heading, small vascular bundles (SVBs) and spikelets per m2 under LN had positive direct effects on ATM(NSC). SVB and spikelets per m2 under LN had larger and positive direct effects, and large vascular bundles had negative direct effects on AR(NSC). TMNSC at heading and SVB under LN had positive direct effects on AC(NSC). In brief, LN supply increased stem NSC accumulation and translocation to developing grain. Components of the source-sink-flow system showed different effects on NSC translocation and contribution to yield formation, depending on genotype and nitrogen level.