Studies On Cotton Varietal Authenticity And Purity Identification By Using SSR Markers

Cotton（Gossypium hirsutum L.）is one of the most important economic crops in China, and itplays a very important strategic role in orderly growth of national economy. People constantly explorethe methods for making the appraisal technology effectively and accurately in practical production, sothat it can protect the lawful rights or interests for cotton farmers and breeders. In recent years,traditional cotton authenticity and varietals purity identification methods already cannot meet theneeds of supervision and regulation, and SSR molecular marker technology can give accurate identityinformation for DNA level, so it becomes a new trend to cotton seeds identification. This researchused SSR molecular marker to carry out a series of applied research, and draw the main conclusionsas following:1) Through preliminary screening and multiple screening processes with typical materials,52primers were chosen as the core primers for cotton SSR molecular identification. The core primers got3~18polymorphism genotypes in96multiple screening materials,299kinds in total, and an averageof5.75; the PIC was from0.22to0.88, with an average of0.61, it revealed that the core primers hadhigher variety identification ability. And EST marker was mainly chosen; because it was morerelevant with phenotype, for a total of30, accounting for57.7%, the others were Genomic markers.2)52core primer pairs were used in the SSR analysis of7conventional cotton cultivars(standard cultivars).24seeds of each cultivar were analyzed in the experiment. The results showedthat among the7cultivars, the maximum number of farraginous seed was9, at least1, and3.9inaverage, and the number of discrepant locis of all the farraginous seed was more than3. Themaximum DNA loci homozygous rate was up to100%, minimum92.3%, and an average of97.0%.The study revealed that the varietals purity and DNA loci homozygous rates are highly positivecorrelated. By SSR marker molecular detection, we can accurately distinguish the impact to the purityof varieties due to genetic factors or seed production procedures.3）In this research, the loci uniformity of5hybrid seeds were detected with52core primers, andgot14heterotypic genotypes, and for the most proportion, heterotypic genotypes had public alleleswith main genotype. The mean ratio of uniformity for E’zamian10, Suza3, Xiangzamian10, ZMS63and ZMS70were0.99,0.94,0.95,0.96, and0.96on52locis. Compared to the other4cultivars, Suza3had9locis that were under0.85on the ratio of uniformity.4) SSR authenticity criterion was explored for6conventional cottons and4hybrid cottons. Theresults showed that for conventional cotton, only commercial seed”ZMS49” whose DNA fingerprintand field traits had high uniformity compare to the standard cultivars, and for other commercialconventional seeds,2commercial seeds were other cultivars instead of the real ones, the other3commercial seeds were mixed with a large number of farraginous seeds in a small amount of the realones. And all the commercial hybrid seed’s DNA fingerprint and field traits had noteworthydifferences compare to the standard cultivars;2commercial seeds were mixed with a large number offarraginous seeds in a small amount of the real ones,2commercial seeds were other cultivars instead of the real ones, and some farraginous seeds in them5) SSR molecular marker was used to detect20batches’ purity of2cultivars (a “Suza” and a“Xiangza”) which came from a seed company, and2chemical emasculation samples in them.Screening the parents’ complementary type primers form26core primers, eventually5primers wereselected for each cultivar. The results showed that the highest purities respectively were76.1%and66.3%in two different batches of “Suza” and “Xiangza”,39.9%and47.4%in average; among thefarraginous plants, maternal selfing plants accounted for the most, and the purity of its parents alsohad a great influence to the genotype of first filial generation.