Increasing the yield potential of rice (Oryza sativa) is the main objective of breeders and cultivators engaged in rice improvement programs. Erect panicle (EP) rice is generally high-yielding with panicles that remain non-curved until maturation. The aim of our study was to evaluate the association of agronomic traits with rice productivity in EP rice. Here, we used the recombinant inbred lines (RILs), crosses between Liaojing5 (erect panicle japonica type) and Wanlun422 (high-yielding indica type). The yield varied among the RILs, and the flag leaf length of EP RILs was negatively correlated with the yield; however, the correlation was not significant in the non-EP RILs. The flag leaf length of the EP RILs was also negatively correlated with biomass increase during the late ripening stage. This may reflect the canopy structure of the EP RILs with short flag leaves which had a larger leaf area index in the lower strata. Additionally, the chlorophyll content in the lower leaf significantly differed among the EP RILs with flag leaves of different lengths, resulting in a higher photosynthetic ability of the lower leaf of EP RILs with short flag leaves. In the present study, an EP line, which has the shortest flag leaf, showed a higher yield than Wanlun422 in both years. EP RILs with short flag leaves might show a higher canopy photosynthetic rate in the later ripening stage; therefore, this trait could be a potential phenotypic marker for achieving high yield of EP rice.
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