Comprehensive Evaluation Of Tea Chrysanthemum ’Qiyuebai’ × ’Suju 7’ F₁ Segregating Progeny And Selection Of Elite Hybrids For Breeding Use

Chrysanthemum（Chrysanthemum morifolium Ramat.）is a perennial flower with rich germplasm resources.Besides high ornamental value,it also can be used for drinkable,medicinal and edible purpose.In recent years,with the improvement of people’s living standards,the demand for tea chrysanthemum with multiple health care functions is also increasing.However,shortage of diversified tea chrysanthemum varieties,and most existing varieties having low yield and poor resistance can not meet the needs of diversified market.At present,few studies has been carried out on the target traits of tea chrysanthemum,and lacking of a systematic evaluation method for tea chrysanthemum made the genetic variation of related traits remain unclear,which limits the breeding efficiency.This current study was set out to explore the genetic variation and heterosis of yield traits,active components,drought and waterlogging resistance in an F₁segregating progeny derived from a cross between tea chrysanthemum cultivars‘Qiyuebai’and‘Suju 7’differing in flowering time and productivity,and a comprehensive evaluation system was established by analytic hierarchy process（AHP）,and some elite hybrid lines with desirable yield and water stress resistance traits were identified as intermediate breeding materials.Findings of this research provide useful reference for developing tea chrysanthemum varieties with high resistance,high yield and quality.The main results are as follows:1.Sixteen yield-related traits of tea chrysanthemum‘Qiuyubai’בSuju 7’F₁hybrid population were investigated.The results showed that each character showed phenotypic variation of different degrees within a range of 7.82%～96.80%.Except for flower diameter,ray flower length,ray flower width,branch number and leaf width,the heterosis of the other 11 traits reached an extreme significance,and the heterosis ratio ranged from-54.42%to 42.45%.The correlation analysis showed that 63 of the 120 pair-wise traits were significantly correlated.Path analysis showed that both single flower fresh weight and plant height had a direct positive effect on yield,and plant height having the largest and positive decision coefficient was the main decision index affecting the yield of tea chrysanthemum.Principal component analysis extracted four principal components,with the cumulative contribution rate up to 72.49%.Combined with membership function analysis,13 elite hybrid lines with high yield,i.e.,QS7-37,QS7-75,QS7-111,QS7-14,QS7-47,QS7-10,QS7-13,P18-26-27,QS7-64,QS7-90,QS7-63,QS7-7 and P18-26-18 were selected.2.The contents of total flavonoids,chlorogenic acid,luteolin and isochlorogenic acid A in F₁hybrid lines were determined.The results showed that the four active components segregate widely,with the coefficient of variation ranging from 20.56%to 64.08%.The contents of total flavonoids,chlorogenic acid,luteolin and isochlorogenic acid A in F₁generation were significantly higher than those in their parents,and the phenomena of transgressive segregation existed.The heterosis of chlorogenic acid,luteoloside and isochlorogenic acid all reached an extreme significance at P<0.01 level,and luteoloside and isochlorogenic acid A showed a maternal inheritance.According to the D value of comprehensive evaluation obtained by the membership function method,10 hybrid lines with desirable active components were screened out,including P18-26-25,QS7-68,QS7-51,QS7-50,QS7-104,QS7-23,QS7-84,QS7-91,QS7-63 and QS7-60.The contents of chlorogenic acid,luteolin and isochlorogenic acid A all met the requirements of medicinal index value of chrysanthemum for tea in Chinese Pharmacopoeia.3.Drought and waterlogging resistance of tea chrysanthemum‘Qiuyubai’בSuju 7’F₁hybrid were tested under two different environments by the methods of potted simulated drought and flooding treatments,and the genetic variation and heterosis of drought and waterlogging resistance were analyzed.The results showed that no significant difference was observed for drought resistance between the two environments.The stress index of drought resistance related traits varied widely among F₁population,with fresh root weight showing largest variation coefficient,and most drought resistance related traits were significantly correlated though with different correlation coefficients.The heterosis of 9drought resistance traits reached an extreme significance at P<0.01 level.According to the value of the membership function,the hybrid population was divided into five grades:high drought resistance,drought resistance,no drought resistance and drought sensitivity,including 2,23,38,17 and 6 lines,respectively.Finally,two high drought resistance lines QS7-24 and QS7-66 were screened out.Waterlogging resistance test showed that there was no significant difference in waterlogging resistance across the two environments.The variation range of the five waterlogging tolerance index was 14.18%～27.64%,and the heterosis of the other four traits all reached an extreme significance at P<0.01 level except for the fresh shoot weight.The comprehensive evaluation by the membership function analysis method divided the F₁population into five grades,i.e.,waterlogging resistance,moderate waterlogging resistance,less waterlogging resistance,no waterlogging resistance and waterlogging sensitivity,including 18,28,24,13 and 3 lines,respectively.16 hybrid lines with higher waterlogging resistance than that of high-parent‘Qiyue Bai’were identified,among which P18-26-6 had the highest MFVW.4.The comprehensive evaluation was made on 36 F₁hybrid lines for yield,resistance,active components,and growth traits.A total of 19 traits were selected as evaluation factors,i.e.,the total flavonoids,chlorogenic acid,mignonette glycosides,chlorogenic acid,Full-bloom stage,single flower fresh weight,dry weight,fresh weight and dry weight per100 flowers,flower diameter,ray floret length,tubular floret number,plant height,crown breadth,branch number,leaf length,leaf width,drought and waterlogging resistance.A comprehensive evaluation system of tea chrysanthemum was established by using AHP,combined with K-means clustering analysis and optimal strain screening.The results showed that among the 19 traits,the dry weight per 100 flowers had the greatest influence on the comprehensive evaluation of F₁hybrids with the weight value of 0.184,followed by the four active ingredients with a weight value of 0.090.Through K-means cluster analysis,36 progenies were divided into 3 grades,i.e.,excellent,good and poor.As a result,6 elite lines,17 good lines,and 13 poor lines were identified,accounting for 16.67%,47.22%,36.11%of the investigated lines,respectively.The 6 elite lines with desirable traits were QS7-14,QS7-23,QS7-43,QS7-75,QS7-111 and QS7-27.