Studies On The Different CMS Applied In The Heterosis Of Cauliflower (Brassica Oleracea Var. Botrytis)

The annual cultivated area and total output of cauliflower of China ranks first in the world,but the yield per unit area has been drceasing in recent years.Cauliflower has strong heterosis,and using CMS is an important approach.However,cauliflower has no CMS of its own,and it faces the bottleneck problems such as narrow genetic background of hybrid parents and large blindness of mating combinations.In this study,the genetic diversity and relationships of 165cauliflower inbred lines were analyzed by using phenotypic characters and SSR molecular markers.According to NC II design,the cytoplasmic effects,heterosis and combining ability and so on of main agronomic and quality characters were studied by using six cauliflowers sterile lines with CMS derived from different sources to provide scientific theoretical basis and guide breeding practice for heterosis utilization of cauliflower.The main results were as follows:1.Based on 10 quantitative traits out of 30 phenotypic characters,the mean coefficient of variation?CV?of the 165 inbred lines was 23.0%,with a range of values from 13.7%to 42.6%.The mean Shannon-Weaver diversity index?H'?of 20 qualitative traits was 0.97 and ranged from 0.21to 1.57.On basis of phenotypic data,the 165 lines were grouped into six different clusters by UPMGA method.Different clusters showed various in curd maturity,plant breadth,leaf color,leaf wax and curd weight,etc.Based on 43 SSR markers,the total number of alleles?Na?was 111 and averaged 2.581 per locus with a range from 2 to 6.The effective number of alleles?Ne?per locus ranged from 1.019 to 3.200 with an average value of 1.599.The average value of Shannon's Information index?I?was0.517,with a range of values from 0.054 to 1.215.The average value of polymorphism information content?PIC?was 0.316,with a range of values from 0.019 to 0.687.The average of Nei's genetic distance ranged from 0.00 to 0.67 with an average value of 0.30.On basis of SSR marker data,the 165 lines were both classified into four categories by NJ cluster analysis and STRUCTURE population structure analysis respectively.The classification patterns presented complex and diverse in geographic origins or curd maturity.The correlation coefficient between the Euclidean distance matrix calculated by phenotypic data and the Nei's distance matrix calculated by SSR marker data was very small?r=0.0406?.It indicated that the 165 inbred lines had abundant phenotypic genetic diversity,but their molecular genetic diversity was rather low.So,the selection of elite parents for hybridization should be done from different clusters having higher inter-cluster distance and larger differences in traits,to aim for higer variability.2.Using six cauliflower CMS lines with cytoplasm from different crops such as rape and cabbage and the corresponding maintainer line as female parents,five caulifolwer inbred lines as male parents,30 paired combinations were made to analyze the cytoplasmic effects on main agronomic and quality traits.It showed that sterile cytoplasm had both positive and negative effects on the main agronomic and quality characters of cauliflower,and showed obvious combination specificity.In general,the CMS cytoplasm derived from rape had significant positive effects on growth period and leaf number,but a negative effect on curd weight.The CMS derived from cabbage showed significant positive effects on curd weight and vitamin C content,while showed significant negative effect on chlorophyll content.The CMS derived from cauliflower presented significant positive effects on growth period and vitamin C content,while presented negative effect on curd weight.It indicated that no cytoplasm of the six CMS lines had ideal effects on all characters,but the adverse effects of sterile cytoplasm on the corresponding traits could be reduced or overcome by selecting appropriate hybrid parental nuclei.3.Heterosis and combining ability of 10 agronomic characters and 5quality characters were analyzed by an incomplete diallel cross involving six CMS lines,eight male parents and their combinations.It showed that both positive and negative heterosis exsited in the main agronomic and quality characters.Among them,on the average of the 48 F₁ combinations,the mid-parent heterosis of curd weight was 12.63%and ranged from-43.46%to 83.09%,and 24 combinations were significant.The mid-parent heterosis of vitamin C content was 16.77%and ranged from-48.50%to 153.93%,and 25 combinations were significant.While the average value of over-parent heterosis in curd weight varied from-46.01%to 60.60%and 10 combinations were significant,the vitamin C content varied from-61.56%to 134.24%and 16 combinations were significant.It indicated that there were significant combinatorial differences in heterosis of yield and quality traits during the different CMS applied in cauliflower.In terms of yield character,CMS lines SH120A,XG108A,YDSL60A and male parents SH120,Shanghai80,R4,R132 had good GCA.In terms of quality character,CMS lines TDXG100A,NB65A,XG108A and male parents SM80,SH120 had good GCA.Considering both yield and quality characters comprehensively,SH120A/Shanghai80,XG108A/SH120 and YDSL60A/R132 were excellent combinations.4.Through correlation analysis between combining ability and F₁observed values,it was found that curd weight,soluble sugar content,chlorophyll content,carotenoid content and soluble protein content were significantly positively correlated with CMS GCA,male parent GCA and?CMS+male parent?GCA,and transverse diameter of curd,lengthways diameter of curd and vitamin C content were significantly positively correlated with CMS GCA and?CMS+male parent?GCA.All the characters were significantly positively correlated with combination SCA.In addition,the correlation coefficients of five characters such as curd weight and vitamin C content with CMS GCA were higher than those of male parent GCA.Through correlation analysis between combining ability and F₁ heterosis,it was found that the heterosis of mid-parent or over-parent in curd weight was significantly positively correlated with CMS GCA or?CMS+male parent?GCA,while the mid-parent heterosis in vitamin C content was significantly positively correlated with male parent GCA.In all characters,the heterosis of mid-parent and over-parent were significantly positively correlated with combination SCA.It indicated that the heterosis of yield and quality traits of cauliflower F₁was closely related to parents GCA or combination SCA,especially related to CMS GCA.5.According to correlation analysis between parental genetic distance with mid-parent heterosis and over-parent heterosis,we found that the genetic distance assesed based on phenotypic data and SSR data could be used for the heterosis prediction of transverse diameter of curd,soluble sugar content,chlorophyll content and carotenoid content,but not for the heterosis prediction of curd weight,lengthways diameter of curd,vitamin C content and soluble protein content.6.The cytoplasmic effects of CMS on the characters related to yield and quality of curd were not significantly correlated with CMS GCA,male parent GCA and?CMS+male parent?GCA,while the cytoplasmic effects of CMS on the content of vitamin C,soluble sugar,chlorophyll and soluble protein were significantly positively correlated with combination SCA.It indicated that the cytoplasmic effect of CMS was relatively independent from parent GCA,but was closely related to SCA of combination quality traits,which confirmed the role of male parent nucleus to hybrid,and also provided possibility for heterosis utilization of CMS derived from different crops.In conclusion,the cauliflower CMS bred from cytoplasmic sterile materials such as rape and cabbage by nuclear replacement showed negative cytoplasmic effects on multiple agronomic and quality characters.However the adverse effects of cytoplasm can be improved by hybridizing parent nuclei.And the heterosis of F₁ with different CMS is closely related to parental GCA or combination SCA,and strong heterosis F₁ should include at least one high GCA or SCA,especially GCA of maternal sterile line.