Grain sorghum has been a significant contributor to global food security since the prehistoric period and may contribute even more to the security of both food and energy in the future. Globally, precise management techniques are crucial for increasing grain sorghum productivity. In China, with diverse ecological types, variety introduction occasionally occurs across ecological zones. However, few information is available on the effect of ecological type on genotype performance and how plant spacing configuration influences grain yield in various ecological zones. Hence, a series of two-year field experiments were conducted in 2020 and 2021 in four ecological zones of China, from the northeast to the southwest. The experiments included six widely adapted sorghum varieties under six plant spacing configurations (two row spacing modes: equidistant row spacing (60 cm) mode and wide (80 cm)-narrow (40 cm) row spacing mode; three in-row plant spacings: 10 cm, 15 cm, and 20 cm). Our results indicated that ecological type, variety, and plant spacing configuration had a significant effect on sorghum yield. Ecological type contributed the highest proportion to the yield variance (49.8%), followed by variety (8.3%), while plant spacing configuration contributed 1.8%. Sorghum growth duration was highly influenced by the ecological type, accounting for 87.2% of its total variance, whereas plant height was mainly affected by genotype, which contributed 81.6% of the total variance. All test varieties, developed in the south or north, can reach maturity within 94-108 d, just before fall sowing in central China. Generally, sorghum growth duration becomes longer when a variety is introduced from south to north. A late-maturing variety, developed in the spring sowing and late-maturing regions, possibly could not reach maturity in the early-maturing region. The row spacing modes had no significant affect on sorghum yield, but the equal-row spacing mode consistently caused higher yields with only one exception; this might imply that equal-row spacing mode was more advantageous for boosting sorghum yield potential. In contrast, decreasing in-row plant spacing showed significant positive linear associations with sorghum grain yield in most cases. In addition, these results demonstrated that sorghum is a widely adapted crop and enables success in variety introduction across ecological zones.

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.

Sorghum is a crucial food crop, and utilizing heterosis is significant for yield enhancement. To classify heterotic groups in sorghum, 96 inbred lines (48 male sterile lines and 48 restoring lines) were previously analyzed using whole-genome resequencing (WGRS) technology, from which 9691 high-quality SNP markers were obtained. In this study, the materials were divided into two groups—Group I (36 lines; predominantly restoring lines) and Group II (60 lines; mainly male sterile lines)—according to their genetic distances, and 8 lines were selected from each group for incomplete diallel crosses, producing 64 hybrid combinations for analyzing ten agronomic traits and their relationship with heterosis and combining ability. Heterosis analysis revealed that yield-related traits (plant weight, grain yield, and single-spike grain weight) exhibited the strongest heterosis, followed by morphological and developmental traits. The general combining-ability variance exceeded the specific combining-ability variance for traits controlled by additive gene effects. The results demonstrate that WGRS technology effectively classifies heterotic groups in sorghum, providing scientific support for parent selection in hybrid breeding. While combining-ability analysis offers higher predictability for heterosis than molecular genetic distance, genetic distance remains valuable for predicting heterosis.

Despite hybrid dominance contributing to the genetic improvement of crops, little is known about heterosis and inheritance patterns of endogenous substances in sorghum (Sorghum bicolor (L.) Moench) root bleeding sap. In this study, six sterile and six restorer lines of sorghum and 36 hybrid sorghum combinations formulated as incomplete double-row crosses were selected as test materials, and heterosis, combining ability, heritability, and their interrelationships of root bleeding sap endogenous substances in different hybrid sorghum combinations and their parents were investigated. The results showed that the root bleeding sap of the F1 generation of hybrid sorghum had a high heterosis in both soluble sugar content and amino acid content at the flowering stage, and the average high-parent heterosis was 129.34% and 74.57%, respectively. Indole-3-acetic acid (IAA), cytokinins (CTK), gibberellic acid (GA₃), abscisic acid (ABA), soluble sugar, amino acid, and root bleeding intensity were mainly affected by non-additive genetic effects of the genes. Soluble protein was affected by additive genetic effects of the genes and had a high narrow heritability (75.50%), which could be selected at low generations in breeding. The combining ability analyses showed that the sterile lines 521A and 170A, and the restorer lines Ji318R and 0–30 were promising parents with high general combining ability. Correlation analysis showed that all endogenous substances of root bleeding sap were positively correlated with the sum of parental general combining ability (GCA) at highly significant levels, and IAA, CTK, GA₃, ABA, soluble sugar, amino acid, and root bleeding intensity were positively correlated with male GCA at significant or highly significant levels. Therefore, the GCA of the restorer lines root bleeding sap endogenous material or the sum of both parents’ GCA can be used to predict the performance of wounding endogenous material in the F1 generation of hybrid sorghum. Overall, this study results can help elucidate heterosis mechanisms of root bleeding sap endogenous material and improve sorghum quality.

Introduction: Improving photosynthetic performance may contribute to the productivity and adaptation of hybrid sorghum in cool regions. This study aimed to characterize stage-specific photosynthetic performance, heterosis, combining ability, genetic effects, and yield performance in sorghum hybrids and their parental lines. Methods: Six maternal lines, six restorer lines, and 36 F ₁ hybrids generated using a North Carolina II mating design were evaluated in field experiments conducted in 2021 and 2022. Leaf light- and CO ₂ -response curves were measured at the jointing, flowering, and maturity stages. Photosynthetic parameters, heterosis, general combining ability (GCA), specific combining ability (SCA), variance components, heritability, heterotic grouping, and grain yield were analyzed. Results: Photosynthetic performance of the F ₁ hybrids varied among developmental stages. At the jointing and flowering stages, the hybrids generally exhibited higher light- or CO ₂ -saturated photosynthetic capacity, Rubisco carboxylation capacity, and electron-transport capacity than one or both parental groups, together with relatively low respiratory or photorespiratory carbon loss. However, apparent quantum efficiency (AQE) was lower in the hybrids at jointing, and several photosynthetic advantages were not maintained at maturity. Carboxylation efficiency (CE), maximum Rubisco carboxylation rate (Vcmax), and maximum electron-transport rate (Jmax) showed positive average mid-parent and high-parent heterosis, whereas photorespiration rate (Rp) and CO ₂ compensation point (CCP) showed negative average heterosis. TAM428A, I15A, L407A, JiR107, T40, and Ji318R showed complementary GCA advantages, while Ji2055A × T40, TAM428A × T40, TAM428A × 0-30, and I15A × 0-30 exhibited favorable SCA effects for multiple traits. Except for dark respiration rate (Rd), SCA accounted for more than 70% of the total combining-ability variance for all response parameters. Broad-sense heritability exceeded 89%, whereas narrow-sense heritability was generally low, indicating a major contribution of non-additive genetic effects. The mean grain yield of the F ₁ hybrids was 50.54% and 54.10% higher than that of the restorer lines in 2021 and 2022, respectively. Discussion: The results demonstrate that photosynthetic advantages in hybrid sorghum are strongly dependent on developmental stage and are largely influenced by non-additive genetic effects. Integrating stage-specific photosynthetic evaluation, parental GCA, cross-specific SCA, and multi-environment yield testing may improve the identification and selection of promising sorghum parents and hybrids for cool-region production.