Sorghum is the main food crop in arid and semi-arid regions of the world, which is of great significance to food security, marginal land use and dietary structure in arid and semi-arid regions. Since the first generation of grain hybrid sorghum was introduced in China in 1958, in order to adapt to mechanized harvesting and reduce labor costs, the plant height of cultivated hybrid sorghum has experienced the change process of high stalk, middle stalk, middle dwarf and dwarf. the green revolution of Chinese grain hybrid sorghum has been completed in the past two decades. This paper summarizes the reasons, history and current situation of grain sorghum dwarfing breeding in China. It shows the trend of decreasing plant height and increasing yield of sorghum varieties in China in the past 60 years. The important germplasms created in the process of green revolution of grain sorghum in China were listed. Through the analysis of genetic relationship, it was found that the dwarf source of restorer line in China came from Chinese local variety Sanchisan, and the dwarf source was traced back to Tx3197B due to the utilization of foreign germplasm Tx3197 A, Tx3197 B. The cloning, variation sites, dwarfing mechanism of sorghum dwarf genes dw1, dw2 and dw3, which play an important role in the green revolution of sorghum, and the contributions of predecessors in exploring new plant height QTLs were reviewed. The dwarfing mechanism of sorghum was different from that of gibberellin regulation system (GA) in rice and wheat. dw1 reduced plant height by regulating the brassinosteroid system (BR) to shorten the length of internodes. dw2 and dw3 encode KIPK protein kinase and auxin efflux transporter (ABCB1), respectively, which regulate the transport of auxin (IAA) to shorten the length of internodes and reduce plant height. The dwarfing genes of dw1, dw2 and dw3 had multiple effects on maturity, spike length, spike grain weight, leaf area while reducing plant height. The distribution and application of dw1, dw2 and dw3 dwarf genes in backbone sterile lines and restorer lines were analyzed by molecular markers and sequencing techniques. It was found that the dwarf genes used more in sorghum restorer lines in China were only dw3, and the combination of dw1dw3 and dw2dw3 formed by dw1, dw2 and dw3 was more widely used in sterile lines. The problems and solutions of sorghum green revolution in China were discussed. It is expected to provide guidance for further improving the process of sorghum green revolution in China and cultivating new germplasm and new varieties with major breakthroughs in yield and stress resistance.
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This study was conducted to screen the concentration of soda saline-alkali stress solution and the determination index of saline-alkali tolerance, to establish the identification method of saline-alkali tolerance to large-scale identification of sorghum germplasms. The saline-alkali tolerance of the core germplasms of grain sorghum were comprehensively evaluated, and the saline-alkali tolerant germplasms were identified and selected to provide a germplasm basis for further breeding of saline-alkali tolerant parents and hybrids.
The main components of saline-alkali soil of in The Songnen Plain are Na2CO3 and NaHCO3. This experiment used 50 mmol·L-1 NaHCO3∶Na2CO3=9∶1 as a stress solution to simulate the moderate saline-alkali environment in Songnen Plain, the pH is 9.19, Salinity is 0.21%. Eight traits, including seedling height, root length, seedling fresh weight, root fresh weight, seeding dry weight, root dry weight, root-shoot ratio fresh weight and root-shoot ratio dry weight were used as measurement indexes and the saline-alkali tolerance characteristics of 285 sorghum core germplasms at seedling stage were identified. Principal component analysis was used to screen the salt-alkali tolerance identification indexes of grain sorghum at seedling stage and establish a mathematical model for salt-alkali tolerance evaluation at seedling stage. The saline-alkaline tolerance of 285 sorghum germplasms was classified by cluster analysis, and the germplasms with strong saline-alkaline tolerance were screened.
50 mmol·L-1 saline-alkali stress showed inhibitory effects on 8 indexes of 285 sorghum germplasms, the average values of saline -alkali resistance coefficients are 0.794, 0.785, 0.565, 0.554, 0.802, 0.638, 0.978, and 0.841. Under saline alkali stress, 8 indexes showed significant positive correlations; the seedling height and root fresh weight could be used as the indexes for the identification and evaluation of soda saline-alkali stress in sorghum seedling stage by principal component analysis; The evaluation model of saline-alkali tolerance characteristics of sorghum seedlings was summarized by multiple linear regression analysis Y=0.097X4+0.171X2+0.201X6+0.157X1+0.105X3-0.147, it can be used for comprehensive evaluation of multiple indicators. 285 grain sorghum core collections were divided into 5 grades by cluster analysis, strong saline-alkali tolerance, saline-alkali tolerance, intermediate type, sensitive type and extremely sensitive type, Among them, there were 8 strong salt-tolerant germplasms, 8 salt-tolerant germplasms, 112 intermediate germplasms, 134 sensitive germplasms and 23 extremely sensitive germplasms. The saline-alkali tolerant germplasm and extremely sensitive germplasm were planted in the moderate saline-alkali soil (pH 8.5-9.5, Salinity 0.3%) for verification in Zhenlai County of western Jilin Province. The average seedling emergence rate of strong saline-alkali tolerant germplasm was 45.4%, and the average seedling height was 23 cm. The average seedling emergence rate of salt-tolerant germplasm was 31.3%, and the average height was 20.9 cm. The average emergence rate of extremely sensitive germplasm was 20%, and the average seedling height was 12.3 cm.
8 strong soda saline-alkali tolerant germplasms and 8 saline-alkali tolerant germplasms were screened out from 285 sorghum germplasms resources with 50 mmol·L-1 soda saline-alkali concentration (NaHCO3∶Na2CO3=9∶1). The seedling height and root fresh weight could be used as the preferred evaluation indexes for the identification of saline-alkali tolerance at seedling stage.
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