Effect Of DEP1 Gene Underlying Panicle Type On Rice Grain Yield And Quality And Its Physiological Function

DEP1 gene regulating panicle morphology,grain number per panicle,and nitrogen uptake and metabolism has been widely used for the breeding of rice yield.However,the dep1 effect on grain quality and yield was background dependent.The difference in yield was mainly attributed to varying degrees of reduction in grain weight under different backgrounds.To clarify the factors influencing effect of dep1 on grain weight and quality,we compared spikelet characteristic and grain quality in superior spikelets and inferior spikelets,and sink,source and flow-related traits between NIL-dep1 and NIL-DEP1 under the Akitakomachi(AKI)and Liaogeng5(LG5)backgrounds.The main results were as follows:1.NIL-dep1 significantly increased grain number per panicle(GNP)by 16.1%–22.7%,produced 11.8%–14.7% higher grain yield,but degraded grain appearance quality in IS compared with NIL-DEP1.2.AKI-dep1 significantly decreased grain weight,processing quality and eating and cooking quality in inferior spikelets(IS)compared with AKI-DEP1,whereas the grain weight and quality,except appearance of LG5-dep1 was similar to those of LG5-DEP1.3.In the AKI background,the peak value of the grain-filling rate of IS in AKI-dep1 was obviously lower than that of AKI-DEP1;AKI-dep1 significantly decreased grain weight in IS from 20 days post-anthesis to the mature stage compared with AKI-DEP1.Whereas the grain-filling rate and grain weight in superior spikelets(SS)did not significantly differ between them.The area of the flag leaves and second leaves in AKI-dep1 were substantially smaller than those in AKI-DEP1.The photosynthetic rate,chlorophyll content,and LAI did not significantly differ between AKI-dep1 and AKI-DEP1.However,AKI-dep1 accumulated significantly lower NSC in the stems(culms and sheaths)than AKI-DEP1 at the heading.No significant differences in number or area of small and large vascular bundles were observed between AKI-DEP1 and AKI-dep1.4.In the LG5 background,the grain-filling rates and grain weights in SS and IS of LG5-dep1 were similar to those of LG5-DEP1 during the grain-filling period.The area of the flag leaves and second leaves in LG5-dep1 were substantially smaller than those in LG5-DEP1.LG5-dep1 exhibited slightly higher but not significant differences in photosynthetic rate and chlorophyll content of flag leaves compared with LG5-DEP1,whereas the LG5-dep1 was significantly lower LAI than LG5-DEP1.No significant differences in the NSC in the stems were detected between LG5-dep1 and LG5-DEP1.LG5-dep1 had a developed vascular bundle system.5.AKI-dep1 significantly decreased grain weight and quality in IS compared with AKI-DEP1,possibly possibly due to a lack of sufficient source supply and adequate vascular system to fully meet the increased sink size.The grain weight and quality,except for the appearance in IS of LG5-dep1,were similar to those of LG5-DEP1,mainly due to a similar assimilate supply and enlarged vascular system.Based on these results,we speculated that the different effect of dep1 on grain weight and quality might be attributed to different source-sink-flow coordination under the two backgrounds.The results provided useful information for improving rice yield and quality through reasonably introgressing or pyramiding the favorable alleles underlying source or quality-related traits by marker-assisted selection.