Sorghum has become increasingly important in China’s agricultural structure adjustment due to its excellent stress tolerance and wide adaptability. To meet the new needs of specialization and mechanization of modern agricultural production, many new achievements have been made in sorghum research. Six articles published in this issue of “Scientia Agricultura Sinica”,introduced the recent research progress of China Agriculture Research System on Millet and Sorghum from the aspects of sorghum genetic selection theory, breeding methods, nutritional quality characteristics and cultivation physiological basis. So as to be helpful to the development of sorghum industry in China.
【Objective】 Sorghum is the main material for liquor-making and brewing well-aged vinegar, and its starch composition and structure are the main factors that influence the brewing quality of sorghum. In this paper, the Dynamic Changes of Key Enzymes Involved in Starch Synthesis are analyzed, the ultrastructure of starch is observed, for confirming the regulatory effect of related enzymes on sorghum starch synthesis, and revealing the ultrastructure characteristics of sorghum starch.【Method】Three sorghum cultivars（Liaonian3, Liaoza19, Liaoza10） with different endosperm types were used as experimental materials. The changes of key enzymes involved in starch synthesis were detected with enzymological technique. Scanning electron microscopy was used to observe the morphology features of starch granules. The regulation of related enzymes in starch synthesis was studied by correlation analysis. 【Result】 The activity of UDPG, ADPG, SSS, SBE, DBE enzymes of sorghum with different endosperm types showed a single peak curve during starch accumulation. The activity of GBSS enzyme of sorghum with waxy endosperm showed a single peak curve, while other types sorghum showed bimodal curves. Activities of UDPG and ADPG, SSS enzyme were significantly correlated with amylose and amylopectin accumulation rate. Activities of SBE, DBE enzyme were positively correlated with amylopectin accumulation rate. Activities of GBSS enzyme was positively and significantly correlated with amylopectin accumulation rate in non-waxy sorghum and semi-waxy sorghum, it showed a positively correlation trend, but not significant in waxy sorghum. For sorghum with different endosperms, the formation process of starch grains showed a similar tendency. The starch accumulation rate was higher during 14-35 d after flowering. The starch grains of waxy sorghum are the smallest, with a diameter within 10 μm, and carved with round-hole or wedge-shaped cavity inside. The starch grains of nonwaxy sorghum are the largest, irregularly globular, with scarcely cavity inside. The size distribution of sorghum starch granules with semi-waxy endosperm ranges widely, most of them with wedge-shaped or star-shaped cavities inside, only a few with no cave. 【Conclusion】 UDPG, ADPG, SSS play important adjustive roles in the accumulation of amylopectin and amylose. GBSS, SBE and DBE are the key enzymes to regulate the ratio of amylose/amylopectin. Higher activities of SBE and DBE are the main reason that makes waxy sorghum contains higher amylopectin. The ratio of amylose/amylopectin may be the main factor affecting the starch grain structure of sorghum.
【Objective】 The heterosis, general combining ability (GCA) and special combining ability (SCA) of main agronomical traits of sweet sorghum were analyzed. Meanwhile, the feasibility of heterosis prediction based on combining ability, phenotypic genetic distance (PGD) and molecular genetic distance (MGD) was estimated. The result will provide theoretical reference for germplasm improvement and hybrid breeding of sweet sorghum.【Method】 Sixty-four hybridized combinations were generated with 8 sterile lines as females and 8 restorer lines as males in accordance with a North Carolina Design II mating scheme. Twelve agronomical traits including days to flowering, growth duration, plant height, panicle length, stem diameter, tillers, panicle weight, 1000-grain weight, grain yield per plot, biomass per plant, biomass per plot and sugar content of hybrids and their parent lines were investigated in two years. The heterosis, GCA, SCA, PGD and MGD were analyzed, as well as the correlation between combining ability, genetic distance and heterosis. 【Result】 Mid-parent heterosis (MPH) of traits from high to low was: biomass per plant, grain yield per plot, panicle weight, biomass per plot, plant height, panicle length, 1000-grain weight, stem diameter, growth duration, days to flowering, tillers and sugar content. Among which, heterosis of growth duration, days to flowering, tillers and sugar content was negative. The sequence of MPH for all traits was almost the same as that of better parent heterosis (BPH). Combining ability analysis showed that the GCA of different parents varied greatly in each trait. Meanwhile, the SCA of different combinations was also significantly different. Most combinations with high SCA also showed high GCA in their parent lines. Heterosis of biomass per plant, grain yield per plot, panicle weight, biomass per plot, panicle length, 1000-grain weight, tillers and sugar content was positively and highly significantly correlated with GCA and SCA of their parent lines simultaneously. Heterosis of growth duration was positively and highly significantly correlated with SCA. Meanwhile, heterosis of days to flowering was positively and significantly correlated with SCA. The PGD of parent lines was 2.86-6.82, and MGD was 0.50-0.96. The correlation between heterosis and MGD was greater than that of PGD in biomass per plant, grain yield per plot, panicle weight, biomass per plot, plant height, panicle length, stem diameter and sugar content. Among which, heterosis of biomass per plot, biomass per plant, panicle length and stem diameter was positively and highly significantly correlated with MGD. 【Conclusion】 Heterosis of yield related traits was higher, and that of sugar content and tillers was lower among all traits. In the prediction of heterosis, combining ability was more effective than genetic distance, therefore, can be used to predict heterosis. MGD was more effective in heterosis prediction compared with PGD.
【Objective】 The aim of this study is to use molecular marker to construct a breeding system to improve the traditional breeding method,thereby reducing breeding costs and improving breeding efficiency. At the same time, it lays a theoretical foundation for the formation of a new breeding system. 【Method】 The F2 population was constructed by crossing the photosensitive(non-heading) forage sorghum variety Jinguang 1R as female and the photo insensitive(heading) sorghum variety BMRC-3-2 as male. According to heading and non-heading phenotypes, F2 population was divided into two groups. Thirty plants were selected from each group and DNA was extracted from leaves, SSR and BSA were used to map photosensitive genes in F2 population of Jinguang 1R/BMRC-3-2 and screen for specific SSR primers. The specific primers were used to identify the photosensitivity trait in F1 generation（F1 Hybrids breeded from high generation stable restorer line with Jinguang 1R as parent and matched with other male sterile lines）, and the final target primers were determined by comparing with the phenotype in the field, so as to construct a new photosensitive breeding system for forage sorghum. 【Result】 After SNP index analysis, the region of about 250 Kb before and after the highest point of 99% threshold line was selected as the candidate region for trait correlation. The total length of the region was 500 kb, with 400 SNP loci, and six of them were non-synonymous mutations or stop gain or stop loss SNP loci. Finally, two candidate genes were identified to be related to photosensitivity, which were located on chromosome 7. A pair of specific primers 70.2-3 was developed by SSR. The primers can distinguish between heading and non-heading sorghum plants to a great extent. The results showed that according to the "single peak" at 251bp, the accuracy of primers 70.2-3 in the identification and selection of 50 non-photosensitive F1 hybrids reached 100%, and all the materials showed a peak value near 251bp. Based on the "double peaks" in the vicinity of 214 bp and 251 bp, the accuracy rate of the primer for the identification and selection of the other 50 photosensitive F1 hybrid species reached 90%. Three materials, No. F1-69, F1-70 and F1-71, showed "double peaks" near 214 bp and 262 bp. Material F1-81 has a "single peak" at 251bp, while material No. 86 has a "double peak" near 251 bp and 232 bp.【Conclusion】 In this study, we revealed that the candidate genes controlling heading date of sorghum were LOC8068537 and LOC8068548, which were between 810000 and 1310000 bp on chromosome 7 of sorghum. The acquisition of specific primers 70.2-3 improved the traditional breeding methods. The primer validation in laboratory could replace the field crossing observation, saving the breeding cost and improving the breeding efficiency.
【Objective】 Sweet sorghum (Sorghum bicolor (L.) Moench) is one of the most important forage crops and is widely cultivated. Studies on biological yield, nutritional quality and forage value of sweet sorghum at different growth stages could provide theoretical guidance for determining the suitable harvesting time of sweet sorghum as forage. 【Method】 Sweet sorghum hybrid, Jitianza No.2, was used as an experiment material, planted in Licheng and Jiyang District in Jinan, and Dongying Cities, and mowed at booting, flowering, milky, dough and physiologic maturity stages. Agronomic and nutritional quality related traits were analyzed, and relative feed values (RFV) at five growth stages were evaluated. 【Result】 The largest value of plant height of Jitianza No.2 were 440.0 cm and 390.0 cm at dough stage in Licheng District and Dongying City, and 445.9 cm at physiologic maturity stage in Jiyang District. Stem is the main component of total fresh weight (TFW) and occupied 83.8%, 83.3%, 78.9%, 78.4% and 78.5% of TFW at five growth stages, respectively. With development of plant, TFW was gradually increased from boot stage to dough stage and decreased at physiologic maturity stage in Licheng District and Dongying City. The maximum TFW were 1 970.5 g/plant and 1 977.5 g/plant. TFW was increased from boot stage to physiologic maturity stage with the maximum TFW of 2 389.4 g/plant in Jiyang District. Total dry weight (TDW) showed the same change trend as TFW, and the maximum TDW of 487.2 g/plant and 469.0 g/plant were reached at dough stage in Licheng District and Dongying City, and 573.5 g/plant at physiologic maturity stage in Jiyang District. Significant effects by environment, growth stage and interaction between environment and growth stage were identified in plant height, leaf fresh weight, stem fresh weight, panicle fresh weight, TFW and TDW. The content of neutral detergent fiber (NDF) was gradually increased with development of plant and the minimum were 45.27% and 46.33% at booting stage, respectively, in Jiyang District and Dongying City. Acid detergent fiber (ADF) content had a similar trend with NDF and the minimum of 29.06% and 32.07% were found at booting stage in Jiyang District and Dongying City. Crude protein (CP) content varied largely in each growth period, with the highest values of 6.29% at booting stage in Jiyang District and 6.83% at flowering stage in Dongying City. Soluble carbohydrate (SC) content was increased significantly at each growth period and reached the maximum of 14.09% and 15.69% at physiologic maturity stage, respectively, in Jiyang District and Dongying City. Ash content was gradually increased with development of plant and the maximum of 8.53% and 5.36% were reached at physiologic maturity stage in Jiyang District and dough stage in Dongying City. Effects by environment, growth stage and interaction between environment and growth stage were significant in NDF, ADF, CP, SC and ash content. With growth of plant, dry matter intake (DMI) at five growth stages was gradually decreased, and the maximum were 2.65% and 2.59% at booting stage in two environments, respectively. Digestible dry matter (DDM) had the same change trend as DMI and the maximum were 66.26% and 63.92% in Jiyang District and Dongying City. Similarly, the maximum RFV of 136.17 and 128.35 were found at booting stage. Significant effects by the environment, growth stage and interaction between environment and growth stage were found in DMI, DDM and RFV.【Conclusion】Biomass, nutritional quality and RFV of sweet sorghum were significantly affected by environment, harvesting stage and environment-harvesting stage interaction. The largest biomass could be obtained at about dough stage, and the highest DMI, DDM and RFV could be reached at booting stage. However, considering the optimal combination of biomass, nutrient quality and silage quality, the optimum harvesting stage was between milk and dough stage.
【Objective】The mechanized production of sorghum is the inevitable direction of future development, and the ideal plant type is the basis and key factor for mechanized production. The dwarf male sterile line 01-26A was found a unique effect in reducing the plant height in F1 generation when crossed with available grain sorghum restorer lines. Therefore, a study was conducted to determine the genetic mechanism and regulation mechanism of plant height dwarfing by its genetic effects and regulatory gene loci. 【Method】This study used sorghum male sterile line 01-26A (A1 cytoplasm) with dwarf plant height effect and sorghum male sterile line 7050A (A2 cytoplasm) without dwarf plant height effect as the test material, focusing on 7 restorer lines, including 6 grain restorer lines and 1 sweet sorghum restorer line, and their cross F1 generation hybrids, the genetic effects of plant height, number of nodes, the total internode length under peduncle, the peduncle length and the head length were analyzed, the gene loci of Dw1 to Dw3 related with the plant height were also measured and analyzed. Dw4 was not included because it had not been cloned.【Result】the male sterile line 01-26A had a significant dwarf effect on the plant height of grain sorghum, and its hybrids is 15.8% lower than that of the 7050A, generally, the absolute value of plant height did not exceed 160 cm. The plant height of F1 generation derived from 01-26A with sweet sorghum restorer line had not been obviously reduced, so it had not dwarf effect on sweet sorghum hybrid. The genetic dwarf effect of 01-26A was mainly manifested in the shortening of the internode length under peduncle, and the internode length under peduncle has more correlated with the plant height variation. The peduncle length reduction of F1 crossed by 01-26A with restorer lines is another reason of plant becoming shorter, but the effect was less than that of the internode length under peduncle. While the head length had much little effect on plant height variation. The dwarf genotype (Dw1 to Dw3) of 01-26A was determined by PCR and sequencing of Dw1 to Dw3 genes. And combined the analysis of plant height genetic data of multiple cross combinations, the plant height genotype of 01-26A was deduced to be dw1dw1Dw2 Dw2dw3dw3dw4dw4, a 3-dwarf sorghum sterile line. In addition, by the analysis of plant height regulation genes, we found that the dw1 and dw3 of 01-26A may had a greater effect on the plant height of grain sorghum, while the presence of DW2 was the immanent cause for not dwarfing on sweet sorghum F1.【Conclusion】 01-26A was likely to be a 3-dwarf sorghum male sterile line with the genotype of dw1dw1Dw2Dw2dw3dw3dw4dw4. It could achieve dwarf regulation of its F1 by reducing the internode length (main effect) and the peduncle length (secondary effect). However, 01-26A, had not been found obvious dwarfing effect when crossed with sweet sorghum, which may be due to the presence of Dw2.
【Objective】In order to identify the genetic effect of early-maturing and dwarf traits on sorghum male-sterile line P03A, here we, provide a theoretical basis for sorghum early-maturing and dwarf breeding improvement by genetic analysis on growth period and plant height. 【Method】In 2016, sorghum male-sterile line P03A,L025A, L080A, L081 and P02A were used as female parent lines, and restoring line L242, L2381, LNK1, L280, L237, and L298 were used as male parent lines the F1 hybrid seeds were obtained by NCⅡ crossing method. And in the winter of 2016, F2 seeds were harvested from F1 selfing plantlets in Hainan province. During 2017-2018, Combining ability analysis on growth period and plant height traits were performed, together with 4 generation conjoint analysis from hybrid F1 and F2 population using mixed major gene plus poly-gene inheritance model. P03A and L237 were selected as female and male parent respectively. 【Result】 Hybrid combination P03A/L237 show the characters of short growth period and short plant height through interaction of the 2 parent lines. P03A contribute to shortening the growth period and plant height in hybrid. Compared with the rest 4 sterile lines, the hybrid combinations with P03A show shorter growth period and plant height, and heritability on the 2 traits was identified. 4-generation analysis of P03A/L237 on growth period and plant height were performed using major gene plus poly-gene inheritance model, which indicate that growth period and plant height traits were both controlled by two major genes with additive-dominate-epistatic effects and poly-genes. Analysis result of growth period suggest that additive effect is higher than epistatic and dominate effects. Heritability of major genes is 81.13%, and heritability of poly-genes is 10.36% respectively. 91.49% phenotypic variation is conducted by major genes plus poly-genes, and 8.51% phenotypic variation is conducted by environmental factors. Analysis of plant height indicate that additive effects and dominant effects of the first major gene are all stronger than the second major gene, and the dominant effect is much more important. Heritability of major genes and poly-genes is 84.80%, and 6.89% respectively. 8.31% phenotypic variation is conducted by environmental factors. 【Conclusion】Genetic effects of growth period and plant height of sorghum sterile line P03A were analyzed in this study. It was identified that the heritability of the two traits mentioned above are relatively high, not easily affected by environmental factors, and with stable hereditary characters. Thus, P03A can be utilized due to its early maturing and dwarf genes in sorghum hybrid breeding, which can meet the requirement of sorghum mechanized production.
