Studies On Cytogenetics And Heterosis Utilization Of Crossing Between Sorghum [Sorghum Bicolor (Linn.) Moench] And Johnsongrass [Sorghum Halepense (Linn.) Pers]

Polyploid is a dominant character in the evolution of higher plants and accounts for up to 70% in grasses. The increases of nutrition volume and nutrition ingredient are the purpose of inducing polyploid. The use of heterosis is one of the most efficient methods for plant breeding in 20th century. The polyplpid and heterosis which are two big superiorities in the nature, will promote the development of heterosis if they are combined in breeding. The cytology behavior and heredity rule in polyploid are different from diploid's, especially in the tetraploid. As is illustrated above, tetraploid sorghum and its distant species, Johnson grass, can be used to breed forage grass suitable in production. Moreover, it will be very important in theory and practice in realizing high yield and good quality using polyploid heterosisThe materials used in this research are tetraploid sorghum line "Sishentian"which by Agricultural University of Hebei. the sterile line tetraploid "TX623A" , the Johnsongrass which has been introduced from USA. and the hybrids Sishentian " × Johnsongrass, tetraploid "TX623A"×Johnsongrass, tetraploid "TX623A"× "Sishentian." Through researching the heterosis, cytology behavior and availability as forage grass of different hybrid and the separated generation, the feasibility of using the tetraploid sorghum and Johnsongrass as forage grass has been determined. Main results illustrated as follows:1.The chromosome configuration of "sishentian",Johnsongrass and their hybrid F₁ at the metaphase I were bivalent and quadrivlent mostly;the sorghum and the Johnson grass were homoeologous and the crossing could reduce the frequency of the lagging chorosome, increase the frequency of the bivalent. Tetraploid sorghum, Johnsongrass and their hybrid were irregular tetraploid genetic population.2.The hybrid of the tetraploid sorghum and the Johnsongrass had powerful heterosis. Natural crossing in the field could get the hybrid and it could be identified through morphologic character of the seeding.3.The heterosis of the biological output and forage grass quality in hybrid of Sishentian" × Johnson grass and in the separated generation F₂, F₃ did not decline.Heterosis can be fixed by perennial root, which was used to produce F2 seed.And then F3 could be used in the next year. Therefore, polyploid heterosis could be utilized generation by generation.4.The crude protein contents of the hybrid of the tetraploid sorghum and the Johnson grass and of their separated generation were highest at the booting stage;the ether estract contents, the energy value of a unit and the biologic yield of a single plant of the hybrid and the separated generation ,were highest at the heading stage. The analysis of nutrition content showed that the content of the effective nutrient was higher and the energy value was highest at booting stage, This period was the best cutting period, and at this stage the crude protein content accounted for 8 -10.3% in the hybrid of sishentian"xJohnson grass ,and it reached 10.36%.in F3...