Primary Study On Screening Of M₁ Variant Plants In Jatropha Curcas L.

With the fast development of global economies,energe crisis has been greatly caused by the rapidly increasing exploitation of fossil energy resources(e.g coal,oil and natural gas) and the finiteness of fossil energy reserves.It is urgent and efficient to search new energy resources, (especially the renewable resources),adjust and optimize the energy structure for the energe crisis. Considering the perspective of sustainable development,the exploitation and utilization of energy plants is an ideal choice for mankind in the future.Energy plants are renewable resources and have the advantages of rich germplasm resources and environmental protection.Jatropha curcas L.is a kind of large shrub/small tree of the Jatropha genus,Euphorbiaceae family,and is also called Gaotong,Choutong,Huangzhongshu,and Jiahuasheng in Yunnan,Sichuan, Guangdong,and Guangxi respectively.It is also called physic nut in some places.Though it is a native species in tropical America,it is widely planted in tropical and subtropical areas around the world.In China,it is mainly distributed in Yunnan,Sichuan,Guizhou,Guangxi,Guangdong,and Hainan.J.curcas is easy to establish,grows relatively quickly and is hardy,being drought tolerant. It is a species with many attributes and multiple uses.Its seeds have high oil content,and the highest oil content of wild J.curcas seed kemel is about 60%,which is beyond Brassica campestris L. and Glycine max(L.) Merr.Study on the seed oil's fatty acid composition,physicochemical properties and cetane number,the results suggested J.curcas seed oil was an ideal raw material of biodiesel.And this "biodiesel" showed more stable flash point,higher freezing point,lower sulfur content,Carbon monoxide emissions,and fixed granular value than diesel fuels "zero" in China. Except for cleaner and more efficient,J.curcas is a renewable resource and has the advantage of lower processing costs.So as an energe plant,J.curcas has a broad prospect for development and utilization. While J.curcas is seen as a very promising energe plant,the main problems of its development are the low seed yield and the limited growing regions caused by poor cold-resistance.One of the efficient ways to change the situation is to combine the classical method of mutagenic breeding with marker-assisted selection(MAS),i.e.,to induce and screen variations artificially so as to obtain the new J.curcas germplasm resources with high yield,good quality and strong resistance.Before J. curcas seeds had been induced by chemical reagents,⁶⁰Coγradiation and low energy ion implantation respetively.This study was carried out after the J.curcas M₁ generation mutagenic plants grown about one and a half years.Through morphologic observation and comparison in the fields,18 phenotypic variant plants had been screened out from 3200 M₁ generation mutagenic plants.The latter study was molecular identification experiment about the selected 18 phenotypic variant plants and 2 control plants mainly using the method of SRAP(Sequence-Related Amplified Polymorphism) markers.The main results were as follows:1.The screening of phenotypic variant plants.From the 3200 M₁ generation mutagenic plants, there were a total of 18 phenotypic variant plants to be screened out.The 18 variant plants were mainly varied in the morphological characteristics of plant type amd whole leaves.The rate of phenotypic variation was very low,only 0.5%.And the rate of phenotypic variation caused by chemical reagents was 0.56%,while the variant rate of ⁶⁰Coγradiation and low energy ion implantation were 0.33%and 0.76%respectively.The highest rate of phenotypic variation about chemical mutation was 0.62%caused by EMS,followed by Nitrosoguanidine 0.55%,and the Colchicine mutation was the lowest,only 0.46%.2.The determination of SRAP-PCR reaction system and the method of silver staining.Due to the established reaction system by the laboratory,some minor adjustments about the reaction factors were made in this study.The results showed the good reproducibility and strong stability of J. curcas DNA amplified electrophoresis maps to be available.By comparison of the two silver staining methods,the Sanguinetti method which showed easier steps and clearer amplified bands had been determined to select finally.3.The detection of SRAP molecular markers.22 pairs of SRAP primers which showed clear amplified bands,stable results and different band patterns were screened out in this study.A total of 266 bands were amplified using the 22 pairs of primers,of which 54 bands were polymorpic,and the polymorpic percentage of bands was 20.3%.The results indicated that mutagenic treatments could cause genetic variation of J.curcas M₁ plants on the molecular level.4.Comparison of the 18 phenotypic variant plants.The molecular detection results implied that 16 variant plants were not only caused morphological variationns,but also caused genetic variations on the DNA level,except for V-6 and V-13 plants.The most 23 polymorpic sites were detected from V-5 plant,and the polymorpic percentage of bands was 9.79%.Followed by V-1,V-8 and V-11 plants,16,10 and 10 polymorpic sites were amplified respectively. 5.Comparison of the three mutagenic methods.J.curcas seeds were induced by chemical reagents,⁶⁰Coγradiation and low energy ion implantation in this study respectively.The molecular detection results indicated the most 54 polymorphic sites was caused by EMS mutation;followed by Nitrosoguanidine,the numbers of polymorphic site were 33;3 polymorphic sites were caused by the Colchicine mutation and the low energy ion implantation respectively;⁶⁰Coγradiation mutation was the least one,only caused 1 polymorphic site.