Molecular Marker-Assisted Selection And Breeding Of New Strains Of Sorghum-Sudangrass Of Super-low Content Of HCN

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 loose spike 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 ISSR fragments related to low content of hydrocyanic acid were selected,cloned and sequence was analyzed for assisted selection of good lines with objective traits from F2 to F5,and the characteristic fragments of ISSR were verified at F5 seedling stage.The new lines were obtained via selecting and breeding.The results of this experiment were as follows:1. The growth rates of hybrids F1 between loose spike Sorghum and four Sudangrass were more than their parents, the average heights were 365～395cm, the period of growth and development was 131～138 days, 9～12 days longer than their paternal, 16～23 days longer than their maternal, they were the late-maturing type; the chromosome pairing in pollen mother cells at metaphaseâ… (PMCMâ… )was regular, the chromosome configurations was 2n=2x=10â…¡,although there are highly homological in chromosomes between loose spike Sorghum and four paternals of Sudangrass,the genetic compositions still have difference among parents.2. The spike types of hybrids F1 were in the middle of their parents,spikes was large, and the spikelets number per spike were more than their paternal;the average number of tillers per plant were 6.27～6.50,which tended to parental; while the sugar brix values in stem at flowering were higher (6.26%～6.53%),which tended to maternal.The fertile pollen rates were above 98%,the natural seed set rates were 73.66% to75.89%,there was no fertility problems.There were significant differences in POD proxidase isozyme zynograms phenotypes in young spikes at heading stage among F1 cross combinations,it can be used as biochemical marker to identify parents and hybrid in protein level.3. The traits were separated in hybrids F2 population,but growth potential was good, the average height was 409～442cm,significantly more than their parents;The growth period was 137～147 day,they were late maturing type;The fertile pollen rates and the natural seed set rates were 94% and 72% respectively,there was no fertility problems.The chromosome pairing in pollen mother cells at metaphaseâ… (PMCMâ… ) was regular.The POD zynograms phenotype of young spikes of F2 separated populations in all cross combinations can be used as genetic markers for selecting excellent strains in cross gener- ation.4. The genomic DNA of four hybrids F1 and their parents were amplified with 14 ISSR primers and 451 ISSR bands were got,the polymorphic rate was 92.2%, ISSR fingerprints can be used as molecular basis to identify parents and hybrids F1.The nine materials can be divided into three groups:group one included loose spike Sorghum, brown shell sudangrass, black shell Sudangrass,white shell Sudangrass,group two included loose spike Sorghum×black shell Sudangrass F1,loose spike Sorghum×white shell Sudangrass F1,loose spike Sorghum×red shell Sudangrass F1,loose spike Sorghum×brown shell Sudangrass F1,group three included red shell Sudangrass;the relatives between loose spike Sorghum and red shell Sudangrass was wider,the relatives between loose spike Sorghum and white shell Sudangrass was closer.5. Eleven specific DNA fragments related to super-low hydrocyanic acid content were screened,loose spike Sorghum×black shell Sudangrass had three specific DNA fragments (900bp,1400bp,1600bp),loose spike Sorghum×white shell Sudangrass had three specific DNA fragments (400bp,750bp,1600bp),loose spike Sorghum×brown shell Sudangrass had two specific DNA fragments (750bp,1500bp), loose panicle Sorghum×red shell Sudangrass had three specific DNA fragments (200bp,1400bp,1600bp).6. The cloned fragments related to super-low hydrocyanic acid content in loose spike Sorghum×black shell Sudangrass and loose panicle Sorghum×white shell Sudangrass were H-1,H-2,H-3 and B-1,B-2,B-3,the fragment length were 1377bp,2268bp,2614bp,1432bp, 1363bp and 2751bp respectively,reading frame were 357bp,279bp,339bp,300bp,228bp, 186bp respectively.The H-1 was 60% in homology with wheat; the H-2 was 63.9% in homology with Sorghum hypothetical protein SORBIDRAFT₀5g027190,and was 62% in homology with rice hypothetical protein OsJ₀7776;H-3,B-1,B-2,B-3 was not homologi- cal with plant,it was presumed that they were new sequence closely relate to super-low hy- drocyanic acid content in Sorghum-Sudangrass.7. The content of hydrocyanic acid in selected lines from F3 and F4 of four cross comb- inations was low(2.58～4.77mg/kg), plant was high (377～405cm), tillers was more (6.21～6.38/plant), growing period was long(132～141d), and the traits were stable in two generations.8. By ISSR molecular marker assisted breeding and selection, four new strains(F5) of super-low content of HCN,loose spike Sorghum×black shell Sudangrass,loose spike Sorg- hum×white shell Sudangrass,loose spike Sorghum×brown shell Sudangrass,loose spike So- rghum×red shell Sudangrass,were obtained.