Poplyploids Induced By Cholchicine Of Two Italian Ryegrass(Lolium Multiflorum Lam.)

Italian ryegrass(Lolium multiflorum Lam.)has great economic benefits because of itstall and fast-growing nature.It has important significance to improve the quantity and quality of the Italian ryegrass germplasm by using polyploidy breeding which may provide potential for selecting new cultivars with high resistance,adaption and good quality.In the present study,colchicine solution with different concentration(0.1 %,0.15%,0.2%,0.25 % and 0.3%)and different treating time(2 h,4 h,6 h and 8 h)were taken to observe the influence of colchicine in the two diploid materials with different backgrounds(PI 376875,cultivar,Italian type,from New Zealand;PI 598939,wild material,Westerworld type,from Italy).The main results were listed as follows:1.After 20 various treatments to germinating seeds of Italian ryegrass,totally 441 individuals which contained 266 individuals(mature rate 33.25 %)from PI 376875 and 175 individuals(mature rate of 21.88%)from PI598939 were succeed to survive till heading.Among them,162 were confirmed by flow cytometre to be tetraploids(90 plants from PI 376875 with induced mutation rate of 33.83 %;72 plants from PI 598939 with induced mutation rate of41.14 %).2.In different treatments,PI 598939 showed greater sensitivity to cholchicine compared with PI 376875.The survival rates of Italian ryegrass were influenced by concentration of solution and treating time.When the concentration was low(0.1%),both of the two materials showed high germination rate(87.5 %-100 %).As the concentration went up,the germination rates dropped.The lowest germination rate(25 %-55 %)was observed in 0.3%treatment.Under the treatment of the same concentration,the germination rates were found to be high(up to 100 %)when the treating time was short(2-4 h).However,lower germination rates(down to 25%)were observed as the time went longer(6-8 h).The mature rates of two Italian ryegrass showed the similar trend as the germination rates that the data went up and then dropped as the concentration and time add.The individuals of wild Westerwolth type material PI 598939 all survived under the treatment of0.1% with 2h while none of those lived when treated by 0.3% with8 h.Induced mutation rate showed a circuitous trace at the same time.Among all the treatments,only 5% individuals of PI 598939 were tetraploids treated by 0.1%with 2 h.The mutant rates came to a peak of 30% and 25% in PI 376875 and PI 598939,respectively,after a 4 h soak in 0.2% solution.As the concentration and treating time added,the mutant rate dropped to a bottom of 12.5 % and 10 % in PI 376875 and PI 598939,respectively.The results showed that afour-hour treatment in 0.2 % solution seems to be the optimum condition for Italian ryegrassin the present study.3.The tetraploids induced in the studies showed differences in agronomic traits including length of secondary leaves,width of secondary leaves,length of flag leaves,width of flag leaves,height of plants,tiller numbers,tiller diameter,length of spikes,spikelet number,comparing with their diploid relatives.The induced tetraploids showed advanced characters in the width of secondary leaves(diploids 4.03 mm,tetraploids 6.56 mm),the length of spikes(diploids 27.86 cm,tetraploids 31.72 cm)and the number of spikelets(diploids 21.02,tetraploids26.81).However,the characters of induced tetraploids including length of secondary leaves(diploids 27.06 cm,tetraploids 21.37 cm),number of tillers(diploids 33.41,tetraploids 28.43)were not as good as diploids.The tetraploids showed no significance with diploids in reproductive stage in length of flag leaves(diploids 14.03 cm,tetraploids 13.43 cm),width of flag leaves(diploids 4.15 mm,tetraploids 4.73 mm)and date of heading(diploids 87 d,tetraploids 91d)with diploid individuals.