Germplasm Innovation Of Crossing Parents For The Production Of Triploid Hybrid Seeds With Heterosis In Purple Coneflower

Purple coneflower(Echinacea purpurea L.Moench)is a perennial medicinal plant belonging to the family Asteraceae and the genus Echinacea.Purple coneflower can significantly enhance the human immunity,has great developing potential and extensive application prospect.In this study,in vitro anther cultures and chromosome doubling technique were used to achieve homogenous diploid and tetraploid purple coneflower plants.By crossing homogenous tetraploid with diploid,triploid seeds with heterosis might be produced.Cultivation by the use of these seeds that combine heterosis with polyploid advantages may have higher economic merit,for it can stabilize the quality of the products and then facilitate the commercial application as substitute to antibiotics.Details of the experiments and the results are as below.Capitulums at suitable developing stages were collected from elite diploid purple coneflower plants in the field.After certain pretreatments and surface-disinfection of the capitulums,anthers were picked out and inoculated onto medium.A total of forty lines of plantlets were regenerated,and then seven homogenous diploid lines with good growing appearances were further selected.These seven diploid lines were treated with colchicine under in vitro culture conditions and seven respective tetraploid lines,after counting the chromosomes in root-tip cells,were obtained.In experiments comparing the effects of the pre-treatments of the capitulums on the induction of calluses from anthers,it was found that water solutions of DA-6 and GA3 had positive effects,and the optimal concentrations were 1.6 mg/l for both of them,while other plant growth regulators of BA,NAA and 2,4-D didn’t have noticeable effects at the concentration range tested.Although pre-treatments of the capitulums with DA-6 and GA3 had positive effects,effects of further supplements of them to the medium were not detected.As for the duration and temperature of the capitulums,3-5 days were found the most suitable.Microscopic observation of the chromosomes in root-tip cells of the regenerated plantlets found that all were diploid without exception.The regenerated plants were generally similar in the appearances of the leaves and petioles,but with quite large differences in the shapes of the root systems among a certain portion of the lines.Those lines which the shape of the roots that was obviously different from the mother line were considered as originating from microspores,and were homogenous.Certification of the origin of the regenerated plantlets is an important step because only those originated from the microspores were homogenous and can be used as parents for crossing to obtain hybrid seeds with heterosis.This finding that the appearances of the roots could be used for comparing to screen homogenous lines,can shorten the time and save labors of cultivation of all the regenerated lines in the breeding program.