Breeding Of New Strains Of Sorghum-Sudangrass Of Super-low Content Of HCN By SSR Molecular Marker

In order to breed new strains of Sorghum-Sudangrass of good agronomic traits and super-low hydrocyanic acid content, four interspecific hybrids F₁ were obtained via crossing between male sterile line of Sorghum and black shell Sudangrass, white shell Sudangrass, brown shell Sudangrass, red shell Sudangrass. The plants of low hydrocyanic acid content and high hydrocyanic acid content were selected from the segregating population of F2 to set up gene pool, some characteristic SSR fragments related to low content of hydrocyanic acid were selected, cloned and sequence was analyzed, and new strains of Sorghum-Sudangrass of super-low hydrocyanic acid content were breeding using pedigree method in combination with SSR molecular marker. The results of this experiment were as follows:1. Hybrids F₁ between male sterile lines Z3A and V4A of Sorghum and four Sudangrasses were tall, growth vigor was strong, heterosis was 13.86%～39.42%.The spike types of hybrids F₁ were in the middle of their parents, tillering ability was strong, fertility was high, the chromosome pairing in pollen mother cells at metaphaseâ… (PMCMâ… )was regular, the content of hydrocyanic acid in selected lines of F₁ was 9.38～42.01 mg/kg, while the sugar brix values in main stem at flowering were 8.89%～9.46%.2. Some characteristic SSR fragments related to low content of hydrocyanic acid were found, the fragment length were 281bp, 219bp and 650bp, which can be used for assisted selection of good lines with objective traits. The results of homology analysis of nucleotide sequences showed that, the homology of TZ1 with complete sequence of cloned BAC 88M4 of Sorghum was 95%, homology with SSR marker genomic sequence of Cyr₃50C of Cyperus rotundus was 90%,the homology of TZ2 with putative receptor protein kinase gene of Sorghum was 75%, homology with microsatellite MRG2713 of Oryza sativa was 88%,homology of TZ3 with sequence of hypothetical protein gene of Sorghum was 96%. Open reading frame analysis showed that there was an assumed open reading frame in length of 126bp in fragment TZ1, encoding 41 amino acids, there was an assumed open reading frame in length of 294bp in fragment TZ3, encoding 97 amino acids; there was not complete open reading frame in TZ2.3.The plant height of three new strains of Sorghum-Sudangrass SLCN01, SLCN02 and SLCN08 was 387.6cm～414.8cm, growth and developing period was 127¹38 days, tillers per plant were 6.16～6.92, the content of hydrocyanic acid was 6.12～7.06mg/kg, the fresh yield were 139935.03～151345.33kg/hm², seed yield were 5662.80～5838.75 kg/hm², crude protein content was14.45%～15.68% at jointing stage, crude fiber content was 24.5%, the sugar brix value in main stems at flowering stage was 10.88%～12.01%, lysine content was 0.422%～0.468%, the chromosome pairing in pollen mother cells at metaphaseâ… (PMCMâ… )were regular, there was no fertility problems.4.Genome DNAs of 11 accessions of sorghum-sudangrass were amplified with nine pairs of SSR primers, 332 SSR loci were got, the percentage of polymorphic loci reached 95.78%. The differences of SSR fingerprint amplified with each pair of primers were significant, the primers could be used for molecular identification of 11 new lines of sorghum-sudangrass (species). Using the GD value of 0.61 as threshold, 11 accessions of sorghum-sudangrass could be clustered into 3 groups: the first group including SLCN01, SLCN02, SLCN03,SLCN09, Mengnong No.3, SLCN10, the second group including SLCN04, SLCN05, SLCN06, SLCN08, the third group including SLCN07.