| Oilseed rape(Brassica napus L.)is extremely important oil crop and economic crop in the world,China is one of the major countries of planting Oilseed rape.However,Sclerotinia sclerotiorum has been persecuting the popularization and plant of Oilseed rape,and it has a strong impact on the yield and quality.The genetic background of existing materials is stenosis.For Sclerotinia sclerotiorum,most species are only tolerance to diseases and lack the resources for high resistance or immunity.Ogu CMS Brassica napus is an ideal breeding material because of its stable sterility and is not affected by environmental factors.This study intends to use the self-crossed progeny of Ogu sterility line hybrid materials S(Rfrf)obtained in the previous period as the female materials,and use the excellently resistant rapeseed derived from artificial synthetic?semi-artificial synthetic and nature group as male materials.Making use of molecular marker-assisted selection and recurrent selection pathways,we intend to select a recurrent line of Ogu CMS-Brassica napus containing with high resistance to Sclerotinia sclerotiorum and evaluate it.The main results of this study are as follows:1.Maintaining sterility and improving resistance to Sclerotinia sclerotiorum in female parents of recurrent selection populationZhongshuang 11 is an excellent conventional rape variety with relatively prominent sclerotinia resistance and is currently widely promoted.In the previous study,we used the heterozygous of Ogu CMS as the female parent and crossed with Zhongshuang 11 and selected the fertile female as the female parent and Zhongshuang 11 to backcross 3 generations in succession to obtain the fertility separation material which has Zhongshuang 11 genetic background.In 2017,the female material was used for the recurrent selection group through the identification of leaf population resistance and stem single plant resistance identification.In the 2018,planting of 11 female materials,the results of leaf resistance identification were comparable to those of Zhongshuang 11.By analyzing the two-year identification results,the correlation coefficient between the two groups was r2017leaf-2018leaf=0.81.The correlation of two years of stem data r2017stem-2018 stem = 0.83,indicating the validity of the data.From the stem resistance results,they all showed extremely significant levels and the resistance value increased by nearly 2 to 4 times,compared with Zhongshuang 11.The stem resistance values for 8D002,8D003,8D006,8D009,8D010 with pollen fertility segregation met our breeding objectives,from which single plants could be used for the next round of recurrent selection.The natural field disease rate(the disease index I)of the female material ranges from 15.45% to 35.42%.According to the result of the quality analysis,a total of 10 singles strains of 8D002-1,8D002-11,8D003-2,8D003-4,8D003-6,8D003-11,8D003-13,8D006-7,8D006-18 and 8D010-18 were selected.2.Screening the male resistant material of recurrent selectionIn 2018,a total of 88 materials were planted for selection of male materials of recurrent selection populations.The sources of the screening materials were classified as artificial synthetic and semi-artificial synthetic rapeseed(hybridized artificial synthetic with Zhongshuang 9)?natural group.In the early stage,molecular marker experiments were performed using the reported resistance marker primers?B.napus A,C-chromosome random primers?and B.rapa-specific primers.We used the results of molecular markers for relative genetic distance and principal component analysis.We selected materials with a genetic distance greater than or equal to 0.25 for screening,of which 53 were genetically consistent with our criteria.The 53 materials contained 36 natural group materials,14 synthetic materials,and 3 semi-synthetic materials.At the same time,we will conduct a cluster analysis of all materials and divide them into three groups named group1,group2,and group3.Group1 has 46 materials,group2 has 25 materials,and group3 has 18 materials.According to the results of PCA,the total genetic variation was mainly explained by the two principal components.The first and second principal components explained the variation of 37.72% and 22.70%,respectively.Combined with the identification of leaf resistance and stem resistance in 2017 and 2018,the results showed that the correlation of leaf resistance in two years r2017leaf-2018 leaf = 0.15(P= 0.4615 > 0.05)did not reach a significant level.The correlation coefficient of stem identification results for two years was r2017stem-2018stem= 0.45(P= 0.0017 < 0.05),which reached a significant level.The stem resistance results were included in the breeding standard of this experiment for evaluation.The relative degree of susceptibility was set to 0.80,and less than or equal to 0.80 met the requirements of this experiment.In 2018,88 male materials were screened,and 59 of them met the relative degree of susceptibility R ? 0.80,including 45 natural groups,12 synthetic materials,and 2 semi-synthetic materials.The natural field incidence(the disease index)of the male of the recurrent selection group was between 11.11% and 37.78%.3.The recurrent selection group parent material will be evaluatedThe male parent material to be screened,because of its wide range of sources,was subjected to a principal component analysis through a molecular marker experiment,and was classified according to the results of resistance identification and quality analysis.The grading standards are based on stem resistance results and genetic distance,and the quality analysis results(oil content,erucic acid content,glucosinolate content)are supplemented.The grade is divided into four,namely I,II,III,IV.We used the results of molecular markers in 2018,stem resistance data,and quality analysis to evaluate 121 seeds of 88 male materials.18 of these seeds reached the level I standard,accounting for 14.88% of the total.There are 68 materials that meet Grade II standard,accounting for 56.19%;Grade III materials are composed of 32 natural group and 2 semi-synthetic materials,accounting for 28.09%;Only 1 part reached grade IV material,accounting for 0.84%,which is 8D090-4.Its stem resistance value,genetic relative distance and quality analysis did not reach the set standards.4.The construction of recurrent selection groupsBased on the evaluation results of S.sclerotiorum resistance,we ferreted the fertile single plant in the female parent material artificially,conferred male pollen with strong resistance to S.sclerotiorum,harvested hybrids,and planted under isolation in the next year.The progeny of the hybrids showed fertility separation,the fertile plants were self-crossed and the sterile plants were free pollinated.At the end of April 2018,indoor identification of Sclerotinia was performed on progeny of hybrids that were deployed in 2017.In combination with the results of fertility investigation and stem resistance,we selected 8D110-11,8D112-5,8D114-2,8D117-3,8D121-3,and 8D121-4 as materials for the recurrent selection group in the next year. |
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