Source-sink regulation and its effects on the regeneration ability of ratoon rice

Ratoon rice is the practice of obtaining a second harvest from tillers originating from the stubble of the previously harvested crop (main crop). The yield formation of ratoon rice crops is dependent on the panicles that regenerated from the stubble of the main crop. The regeneration ability is an index that is used to evaluate the germination quantity of regenerated buds. The source-sink relationship was closely related with regeneration ability of ratoon crop. However, the influence of source-sink regulation on the regeneration ability of ratoon rice has rarely been studied. Field experiments were conducted to examine the effects of source-sink regulation through leaf-cutting and spikelet-thinning on the regeneration rate of ratoon crop in central China in 2017 and 2018. The treatments included three leaf-cutting and two spikelet-thinning treatments, which were conducted at the full heading stage of the main crop. Spikelet-thinning increased the regeneration rate of ratoon crop by 20.9% in 2017 and 32.5% in 2018 as compared with the treatments with no spikelet-thinning. However, leaf cutting decreased the regeneration rate of ratoon crop by 28.9% in 2017 and 7.6% in 2018 compared with the treatments with no leaf-cutting. The effects of spikelet-thinning on the regeneration rate were decreased as the number of cutting leaves increased. The negative effects of leaf-cutting on the regeneration rate were reversed by the treatment of thinning one half of spikelets. The regulatory effects of leaf-cutting and spikelet-thinning on regeneration rate were associated with the changes in the ratio of grain number to green leaf area, stubble dry weight and non-structural carbohydrates content in the stubble.