Pedigree Analysis Of Cabbage Varieties Released In China And Genetic Effects Of Founder Parent01-20

Cabbage (Brassica oleracea var. capitata) is a major vegetable crop widely cultivated in the world.More than200cabbage varieties of different types have been developed and released since the1950s and1960s in china. But the pedigree analysis of cabbage varieties was far behind many major crops, andmany cabbage varieties’ pedigree were unclear. The analysis of pedigree could not only find the rule ofcultivar succession, predict breeding objectives, but also reveal the rule of parental selection andcombination, provide guidance for the breeding of new cabbage varieties. The analysis of pedigree wouldbe conducted to clarify the founder parent phenomenon in cabbage. Several specific chromosomal lociand regions associated with important agronomic traits could be detected based on the revealing ofgenetic composition and breeding effects of founder parents. This study will improve the accuracy andefficiency of parental selection in cabbage breeding, and provide theoretical guide for the the creation ofnew founder parents.Based on the pedigree analysis of cabbage released,01-20(founder parent), other four sister lines(non-founder parents) and their derived lines, DH population from founder parent01-20and96-100wereused as materials for discovering specific chromosome loci and regions of founder parent01-20. Theconstructed high density linkage map and QTL analysis could clarify the relations between specifical lociof founder parent and important agronomic traits and elucidate the breeding effect of specific loci orregions.1. There were219cabbage varieties released during1982－2012in china, which included183hybrids, accounting for83.56%. The hybrid proportion reached96.74%in recent10years. The analysisof176varieties with known parental origination indicated that all the varieties were combined with261parental lines, which could be traced to171original resources, i.e.67domestic landraces and104alienaccessions. In all the original resources, the number of Heiyexiaopingtou derived varieties was the most(38), followed by Beijingzaoshu (27). The pedigree analysis showed that the combinations with twoparents from different geographical area or having great botanical characteristic difference always hadstrong heterosis. The rule of parental selection and combination was revealed based on the parentalcharacteristic of several major varieties in China. Pedigree of foundation parents Beijingzaoshu01-20and Heiyexiaopingtou21-3were drawn in this study.2. Polymorphism between parent01-20and96-100was screened with978EST-SSR,2173Scaffold-SSR,707Indel primer pairs. The polymorphic markers of273SSRs and261Indels weredetected. The linkage map has placed406SSR and Indel loci into nine groups. The map covered934.06cM, and average marker interval was2.3cM. All nine linkage group was assigned to nine chromosomeswith anchored markers.3. QTL analysis was performed to determine the markers associated with important agronomicaltraits of plant, leaf, head and seed, quality and disease resistance, according to the results of three seasonsin2011-2012. A total of171QTLs were detected for33agronomical traits. There were58QTLs for plant and leaf traits, and the number of QTLs (R2>10%) was38;57QTLs for head traits,38QTLs(R2>10%) and11QTLs were repeatedly detected in different seasons;38QTLs for leaf color and headcolor traits,26QTLs (R2>10%);11QTLs for quality and disease resistance traits,10QTLs (R2>10%);seven QTLs for silique and seed traits, five QTLs (R2>10%). These QTLs could be used for clarifing therelations between specific loci of founder parent01-20and important agronomic traits, and elucidatingthe breeding effect of specific loci.4. Several QTL clusters had been found on regions of chromosome1,3,7and9. The region in55.9～60.9cM on Chr.1contained nine plant and leaf trait QTLs and seven head trait QTLs. The regionof88～92cM on Chr.3contained five plant and leaf trait QTLs, seven head trait QTLs and one headcolor trait QTL. The region of27.8～30.9cM on Chr.7contained four head trait QTLs and two headcolor trait QTLs. The region of58.6～61.5cM on Chr.9contained three head traits QTLs, three leafcolor trait QTL and three quality and disease resistance traits. These regions provided importantreferences for the QTL fine mapping and cloning.5. According the phenotype comparison of founder parent01-20with other5sister lines, thefounder parent01-20had good comprehensive traits and no obvious defects. It not only inherited theearly maturity, but also improved in leaf color, head color and quality traits. The polymorphic patternsamong six sister lines showed that01-20had one unique allele,01-07-258had one unique allele,01-20and01-07-258had five same alleles which were however different from the other four sister lines.Based on the QTL analysis, there are five specific loci of founder parent associated with importantagronomic traits, which could elucidate the breeding effect of specific loci. Founder parent01-20possessed the greener outer leaves, smaller plant expansion, rounder head shape, less core length andbetter quality. The loci of Indel64on Chr.3and Indel353on Chr.9have significant cluster and geneticeffect.