Effects of erect panicle genotype and environment interactions on rice yield and yield components

The dense and erect panicle (EP) genotype conferred by DEP1 has been widely used in the breeding of high-yield Chinese japonica rice varieties.  However, the breeding value of the EP genotype has rarely been determined at the plant population level.  Therefore, the effects of the interaction of EP genotype and the environment at different locations and times on rice yield and its various components were investigated in this study.  Two sets of near-isogenic lines (NILs) of EP and non-EP (NEP) genotypes with Liaojing 5 (LG5) and Akitakomachi (AKI) backgrounds were grown in the field in 2016 and 2017 in Shenyang, China, and Kyoto, Japan.  In 2018, these sets were grown only in Kyoto, Japan.  The average yields of the EP and NEP genotypes were 6.67 and 6.13 t ha⁻¹ for the AKI background, and 6.66 and 6.58 t ha⁻¹ for the LG5 background, respectively.  The EP genotype positively affected panicle number (PN) and grain number per square meter (GNPM), mostly resulting in a positive effect on harvest index (HI).  In contrast, the EP genotype exerted a negative effect on thousand-grain weight (KGW).  The ratio of the performance of the EP genotype relative to the NEP genotype in terms of yield and total biomass correlated positively with mean daily solar radiation during a 40-day period around heading.  These results indicate that the effectiveness of the EP genotype depends on the availability of solar radiation, and the effect of this genotype is consistently positive for sink formation, conditional in terms of source capacity, and positive in a high-radiation environment.