Expression of Heterosis in Photosynthetic Traits in F1 Generation of Sorghum Hybrids and Relationship with Yield Traits

Abstract

Abstract Heterosis plays an important role in improving crop yield. Understanding the expression of heterosis for photosynthetic physiological traits in sorghum is important for breeding sorghum varieties with strong hybrid dominance. In this study, six sorghum restorer lines and six sorghum sterile lines and their thirty-six hybrid combinations formulated according to the NCII incomplete double-row hybridization method were used as materials, and the performance of hybrids in the F1 generation of hybrids in terms of hybridization in leaf photosynthesis-related parameters and carbon metabolism-related enzymes and their correlation with yield traits were analyzed at the flowering stage. The results showed that net photosynthetic rate (Pn), transpiration rate (Tr), stomatal conductance (Gs), apparent leaf meat conductance (AMC), ribulose-1,5-bisphosphate (RuBP) carboxylase, phosphoenolpyruvate (PEP) carboxylase, and sucrose phosphate synthase (SPS) of hybrid sorghum showed significant high-parent heterosis, while inter-cellular carbon dioxide concentration (Ci), water use efficiency (WUE), and sucrose synthase (SuSy) mainly showed negative heterosis, a few showed high-parent heterosis. Thousand grain weight (TGW), grain weight per spike (GWPS) and dry matter content (DMC) all showed high high-parent heterosis, with the highest value of 82.54% for thousand grain weight (TGW). Meanwhile, Pn was positively correlated with Tr, Ci, Gs, RuBP carboxylase, PEP carboxylase, GWPS, TGW, and DMC, which indicated that Tr, Ci, and Gs could assist in the screening of high-photosynthesis sorghum varieties and that Pn could assist in the screening of carbon-efficient sorghum varieties, and that Pn was closely related to yield. In summary, the F1 generation of sorghum hybrids has shown significant heterosis at anthesis. Combined with the field performance, the Pn at anthesis can be used as a reference for early prediction of the yield potential of the F1 generation of sorghum hybrids and screening of carbon-efficient sorghum varieties.