Early Selection And Molecular Identification Of Medicinal Plant Fagopyrum Dibotrys (D.Don) Hara By Gamma Radiation

Buckwheat(Fagopyrum dibotrys(D.Don.) Hara.),an erect perennial herb of Polygonaceae,whose rhizome is a traditional folk medicine for treatment of lung abscess, dysentery,rheumatism and tumefaction.It had been one of the "List of National Key Conservative Wild Plants in China(the first group) "because of destruction by blind harvest and environment pollution.γray had been one of the most efficient ways to create mutants in plants,with the advantages of convenient operation,short cycle and high somatic mutation.Buckwheat rhizomes of Beijing introduced from Jiangsu of green stem were radiated byγray with dosage of 0,5,10,15,20 and 30Gy at rate of 2.005Gy/min.Red stem mutants were induced in 5,10,15 and 20Gy of M₂ genenration.Agronomic traits, photosynthesis and chlorophyll fluorescence,antioxidative enzymes and(-) epicatechin of selected green and red plants were analyzed in the paper,and AFLP technology was applied for genetic diversity.Results showed as followed:(1) Radiation enhanced the flowering and root yield of green stem buckwheat,while delayed those of red mutant.In addition to the obvious inhibition of plant height,there were no significant effect on the other agronomic traits,such as number of branches, number of main stem,petiole length and leaf area during all period.All traits of green plant were larger than red mutant except for petiole length under the same radiation dose.(2) Chl a,Chl b and Chl a+b of green buckwheat were higher compared with control,while those of red mutant lowered,both decreasing with elevating dose ofγray.Car content of both green and red buckwheat was contrasted to Chl content,respectively.There was no significant effect on Chl a/b of green buckwheat,but that of red mutant increased byγradiation.P_n,Gs and WUE of both buckwheat reduced while Tr increased byγray,and Ci decreased withγray increasing,which showed that leaf photoinhibition was the result of stomatal limitations.Fluorescence parameters,such as F_o,F_v/F_m,ΦPS2,ETR and qP declined significantly as compared with control due to leaf photoinhibition during seedling and growth stage, while enhanced in flowing.NPQ increased significantly to protect PS2 by enhancing thermal dissipation during all period.Chlorophyll content of green buckwheat was higher than red mutant during all period, carotenoids just higher in flowering period under the same radiation dose.P_n,F_o,F_v/F_m and qP of green buckwheat were higher than those in red mutant in seedling and growth stage, while lower in flowering period.NPQ of red mutant were higher than green one on the whole period.(3) Membrane permeability,antioxidative enzyme and flavonoids are the significant index resistant to radiation.Membrane permeability was accelerated byγradiation,and MDA content increased as the result of membrane oxidation.The physiological index,such as SOD,CAT,APX,GR and flavonoids were significantly higher than those in control. Except that SOD,POD,CAT and anthocyanin content decreased in some period,others increased gradually with rising dose ofγray.Membrane permeability,SOD and flavonoids of red mutant were higher than those in green during all period under the same radiation dose,that opposited to GR.POD and APX of green buckwheat were higher than those of red mutant in seedling and growth period, while decreased in flowering period;that were contrary to CAT.MDA and anthocyanin of green buckwheat were higher than those of red mutant in seedling and flowering period, while decreased in growth period.(4) Active ingredient of buckwheat was affected significantly by radiation treatment.There was significant difference between that of green buckwheat and control except for 15Gy (p＜0.01),and between red mutant and control except for 5Gy(p＜0.01).(-)-epicatechin content of plant radiated byγray was higher compared with control,with high value of 0.0841%in 20Gy of green buckwheat and 0.1027%in 15Gy of red mutant.It was feasible to improve(-)-epicatechin content of buckwheat byγradiation.(5) AFLP technology was applied in mutant identification and selection to improve the breeding efficiency at the early stage.944 pieces of clear bands were amplified by 8 pairs of primers combinations,of which 700 were polymorphic with an average polymorphism site of 73.99%.UPGMA showed the resemble index from 0.74 to 0.87.Genome variation of buckwheat was positive related to radiation dose.In conclusion,buckwheat adapted to radiation injury through lower chlorophyll content,higher antioxidative enzyme and active ingredient content.(-) epicatechin content and genetic diversity increased byγradiation.The application ofγradiation opened new field for medicinal plants variety selection,and had great significance in yield and quality improvement.