Expression of heterosis in photosynthetic traits in F1 generation of sorghum (Sorghum bicolor) hybrids and relationship with yield traits

Abstract

Heterosis is a crucial factor in enhancing crop yield, particularly in sorghum (Sorghum bicolor). This research utilised six sorghum restorer lines, six sorghum sterile lines, and 36 hybrid combinations created through the NCII incomplete double-row hybridisation method. We evaluated the performance of F1 generation hybrids for leaf photosynthesis-related parameters, carbon metabolism-related enzymes, and their correlation with yield traits during the flowering stage. Results showed that hybrid sorghum exhibited significant high-parent heterosis in 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). Conversely, inter-cellular carbon dioxide concentration (Ci), instantaneous water uses efficiency (WUE), and sucrose synthase (SuSy) displayed mostly negative heterosis. Traits such as 1000-grain weight (TGW), grain weight per spike (GWPS), and dry matter content (DMC) exhibited significant high-parent heterosis, with TGW reaching the highest value of 82.54%. Pn demonstrated positive correlations with Tr, Ci, Gs, RuBP carboxylase, PEP carboxylase, GWPS, TGW, and DMC, suggesting that Tr, Ci, and Gs could aid in identifying high-photosynthesis sorghum varieties. Concurrently, Pn could help select carbon-efficient sorghum varieties due to its close relationship with yield. Overall, the F1 generation of sorghum hybrids displayed notable heterosis during anthesis. Combined with field performance, Pn at athesis can serve as a valuable indicator for early prediction of the yield potential of the F1 generation of sorghum hybrids and for screening carbon-efficient sorghum varieties.