Evaluation Of Allelopathic Wheat Germplasm And Its Genetic Diversity Study

The application of allelopathy is an alternative weed control method that could be incorporated into integrated weed management package,thereby reducing over-reliance on herbicides and decreasing environmental pollution.Research in this area has been receiving increasing attention in the world,but it is also possible to identify a range of researchable areas that still need attention,such as laboratory screening,the mechanism of allelopathy expression under environment strssses,indentifying allelochemicals really responsible for weed reduction in the firld,searching for the gene involving in wheat allelopathy,etc.In this paper,a laboratory screening was conducted to study the allelopathic potential of 90 wheat varieties from home and abroad by Soil Agar Sandwich Method.Then the ability of weed-suppression and agronomic characters were evaluated in the field,then three wheat varieties which were selected for allelopathy breeding were used to extract its allelochemicals,and they were identified by GC-MS.Genetic diversity of 67 representive wheat varieties was detected by using ISSR markers.The results were summarized as follows:1,Of 90 wheat accessions,5 varieties showed strong allelopathic potential by significantly inhibiting root growth of Lettuce(Lactuca sativa L.)in the laboratory screening.The same result was found in the field screening.Correlation between the laboratory screening and the field experiment showed that field performance could be predicted to some extent by Lactuca sativa L. root length reduction in the laboratory.The result demonstrated that there was a considerable genetic variation of alllelopathic activity in wheat germplasms and the alllelopathic activity was easily affected by environment.2,At the level of D=39.2,67 wheat varieties were clustered into six groups.The first group consisted of 24 accessions,showing strongly allelopathic effect on the target,of which 8 varieties performed less than 29.2%inhibition in the suppression of the receivor plant,such as "Fufan 4056-1","19101-110" and "A246" and so on,their hierarchical characters were comparatively better,which could be used as CK sources for the investigation of wheat allelopathy.The fouth group included 14 accessions,,and the averaged IR value was 60.8%,their yield traits were relatively better,.whch could be recommended as useful sources for the investigation of wheat allelopathy and the breeding program for allelopathic cultivars.3,The allelochemicals were extracted from wheat roots and rhizosphere soil using with liquid nitrogen grinding and ultrasonic broking.According to GC-MS analysis,It showed that root extracts in different allelopathic potential wheat by water mainly contained phenolic acids,alcoholic,carboxylic acid,ester,purine,hydrocarbon,phenolic,steroid,ketone,and hydroxamic acids.Rhizosphere soil extracts mainly were consisted of acid,ester,alkaloid, phenolic acids,alcoholic,ketone,and hydroxamic acids.The chemical composition in different tissue extracts is different.The result suggested that phenolic acids(Benzoic acid,Succinamic acid, 3,4-Dimethoxymandelic acid,Cinnamic acid,p-(hydroxy)-3-methoxy-4-hydroxylcinnamate)and hydroxamic acids(Propanoic acid.2-(methoxyimino)-)might be ones of allelochemicals. However whether there are the other kind of allelochemicals is needed to further study.4,Genetic diversity in 67 accessions was evaluated using inter-simple sequence repeat(ISSR) markers.A total of 80 ISSR primers were screened,of which 10 polymorphic and informative patterns were selected to determine the genetic diversity and genetic relationships.Total of 87 bands were amplified,of which 66 were polymorphic(about 71.3%).The size of the bands ranged from 240bp to 2000bp.Six to fifteen polymorphic bands could be amplified from each primer with an average of 8.7 bands.The genetic similarity(GS)value based on ISSR markers among 67 accessions of wheat was ranged from 0.71 to 0.97.All 67.accessions could be distinguished completely by ISSR markers.In summary,ISSR is a suitable and effective tool to evaluate genetic diversity among allelopathic barley germplasms.5,According to the clustering results,all of the collected accessions could be classified into 7 groups based on the genetic distance(D=0.16).Of which 35 accessions were in the first group corresponding to an average of 44.7%inhibition rate,however the second group included 17 accessions,showing higher allelopathic potential.The third group included five accessions showing high allelopathic potential with an average of 61.0%inhibition rate.The four group included seven accessions showing low allelopathic potential with inhibition rate between 10.1% to 38.8%,and the averaged inhibition rate was 25.2%.The other four landraces were independent clustered in the fifth,sixth and seventh groups respectively,and IRs of the fourth accessions were 26.6%,12.2%and 55.7%respectively.It was suggested that the cluster was significantly associated with the genetic races and different geographical regions.It was found that some wheat accessions with higher allelopathic potential were clustered together,implying that the gene conferring allelopathy might be isolocus.However,some cultivars with different allelopathic potential could be clustered into the same group,performing lower level of genegtic polymorphism,which was attributed to oriented selection for the other traits in breeding program.In conclusion,we selected that "115/Qing Hai Mai" and "92 L89" with strong allelopathy as a useful source for the research on wheat allelopathy and the breeding program for allelopathic cultivars,"Kang-10103(80)" with low allelopathic potential could be used as a control source for the investigation of wheat allelopathy and its hybrid breeding to improve the utilization of germplasm resources and breeding efficiency,and promot the development of the production and crop breeding.