A better root morpho-physiology after heading contributing to yield superiority of japonica/indica hybrid rice.

Highlights • JIHR had considerable yield superiority over JIR and IHR, attributed mainly to the larger sink through more spikelets per panicle. • JIHR had the better root mopho-physiological traits during grain filling compared with JIR and IHR. • The better root mopho-physiology of JIHR could contribute to the shoot stay-green traits, higher biomass accumulation, and its yield superiority. Abstract Grain yield superiority of japonica/indica hybrid rice (JIHR) over japonica inbred rice (JIR) and indica hybrid rice (IHR) was reported, and some shoot traits underlying high yield of JIHR were identified, like shoot stay-green traits after heading. To date, little information has focused on root trait differences among JIHR, JIR and IHR. Besides, improved shoot stay-green traits after heading of JIHR might indicate better root morpho-physiological traits after heading compared with JIR and IHR, considering the interdependent relationship between root and shoot. In this study, two JIHR, two JIR, and two IHR were planted in 2014 and 2015 at Ningbo, and in 2015 and 2016 at Yangzhou, China. JIHR showed longer total growth period especially the period from heading to maturity and higher grain yield per day, and 5.6–19.8% higher grain yield compared with JIR and IHR across two years at two sites. JIHR had consistently higher root and shoot biomass at heading and maturity at two sites compared with JIR and IHR. Higher root length and root volume, and more roots in the 11–30 cm soil depth at heading and maturity of JIHR over JIR and IHR were observed across years and sites. JIHR had not only higher leaf SPAD value and leaf photosynthetic rate, but also higher root bleeding rate and root oxidation activity during grain filling, compared with JIR and IHR. JIHR had lower reduction rate of root biomass, length, volume, bleeding rate, and oxidation activity from heading to maturity than JIR and IHR at two sites. Root length and root volume were correlated positively (P < 0.01) to shoot biomass at heading and maturity and rice grain yield. Root bleeding rate and root oxidation activity were correlated positively (P < 0.01) to leaf SPAD value and leaf photosynthetic rate during grain filling and rice grain yield. Our results suggested that better root morpho-physiological traits (showing as longer, larger, deeper, and more active roots) after heading of JIHR could contribute to the shoot stay-green traits, higher biomass accumulation, and finally yield superiority over JIR and IHR. [ABSTRACT FROM AUTHOR]