In order to analyze the genetic diversity of tropical sorghum germplasm resources, screen for superior sorghum germplasms, and to provide a critical support for the innovation of sorghum germplasm and the breeding of the new cultivar that with high-quality and high-yield in the temperate regions of northern China.

Taking 70 tropical sorghum germplasm resources as test materials, and 10 phenotypic traits of the test germplasm resources were observed in the field. Multiple statistical methods such as Shannon-Weaver diversity index, correlation analysis, cluster analysis and principal component analysis, stepwise regression analysis were comprehensively applied for the analysis and comprehensively evalution the genetic diversity of tropical sorghum germplasm resources in the temperate region of China. Molecular marker-assisted selection combined with conventional hybridization was used to carry out target trait design breeding, and a new high-quality and high-yield forage sorghum variety with both bmr and PS genes and safe seed production in the northern temperate regions was bred.

The phenotypic variations of the germplasm resources were abundant, and the diversity indices of the 10 traits ranged from 1.44 to 2.00. Correlation analysis showed that the plant height was extremely significantly positively correlated with stem diameter, number of leaves, leaf length, leaf width and biological yield. The growth stage was extremely significantly positively correlated with Brix, but extremely significantly negatively correlated with plant height, stem diameter, number of leaves, leaf length and biological yield respectively. Cluster analysis divided 70 resources into 3 groups with significant differences in phenotypic characteristics. Principal component analysis reduced 10 trait indicators to 5 independent principal components, with a cumulative contribution rate of 85.921%. 10 elite resources including IS 18542 were selected based on the comprehensive evaluation scores (F value). The stepwise regression analysis showed that all of the 10 phenotypic traits could be used as key indicators for the comprehensive evaluation of forage sorghum. 3 photoperiod sensitive resources of Ma5/Ma6 genotype were identified, excellent parents lines 74A, 1390R and 107R and the new silage sorghum variety Long mu No.1 that with high-quality and high-yield was bred by molecular design breeding.

Based on the genetic diversity analysis and comprehensive evaluation of phenotypic traits, the extensive phenotypic variations and rich genetic diversity of tropical sorghum germplasm resources in temperate regions were clarified, and the 10 key indicators for the comprehensive evaluation of forage sorghum germplasm resources were determined. The genes pyramiding breeding had discovered and created excellent parents with both bmr gene and PS genes, and the new forage sorghum variety with high-quality and high-yield was bred, indicated that the forage quality and yield were improved at the same time.