Phenotypic Correlation Among Root and Shoot Traits in an Elite Chinese Hybrid Rice Combination and Its Three Derived Populations

To elucidate the phenotypic correlations among root and shoot traits in elite hybrid rice (Oryza sativa L.), 7 root and 10 shoot traits in an RIL population of Xieyou 9308 and 2 reciprocal backcross populations (BCF₁) derived from the RILs were determined under hydroponic culture and field experiment conditions. All traits, except for root diameter, panicle number per plant and grain-setting rate, were significantly different between the 2 recurrent parents, and transgressive segregations and continuous distributions were observed in either root traits or shoot traits in the RIL or BCF₁ populations. In the root traits, root length was positively correlated with total root length, dry root weight, root surface area, root volume, and number of root tips; however, root diameter was negatively correlated with other root traits. In the shoot traits, heading date, plant height, panicle length, spikelet number per panicle, grain-setting density, and grain yield per plant showed significant and positive correlations with all root traits except for root diameter. These results provide applicable shoot indices for indirect selection of root traits and valuable information for super hybrid rice breeding.