| Chrysanthemum(Chrysanthemum morifolium Ramat.)is one of the four major cut flowers in the world.Because of its rich varieties,rich flower patterns and colors,and long vase life,it is deeply loved by consumers.Among the standard large-flowered cut chrysanthemums,rosettes and peony types rank the largest part.Recently,the pompon type become popular owing to its round and full flower shape like "pompon",but they are mainly imported from Europe and America with low diversity and few choices of producers and consumers.Therefore,it is very urgent to select new pompon cut chrysanthemum varieties with independent property rights,which are rich in color,full and compact in shape and vigorous in growth.In pompon cut chrysanthemum,crossbreeding between some genotypes often yielded few seeds.This study was set up to overcome the hybridization obstacles and improve the breeding efficiency,to investigated the genetic performance of pompon-related flower traits by using the main gene plus polygene hybrid genetic model,and to construct a comprehensive evaluation method for the selection of superior hybrids with improved pompon traits.Results from this study can provide a reference for the efficient breeding of new pompon cut chrysanthemum varieties.The main results are as follows:1.The pollen viability,pollen germination and embryonic development were investigated in the two crosses,’Huangpingpang’×’Nannong Hongpingpang’ and’Baipingpang’ ×’Nannong Hongpingpang’,and the effects of five different pollination treatments,including three times of pollination,mixed pollination,100 mg/L 6-BA,100 mg/L NAA and 50 mg/L GA on the seed setting of ’Momoko’×’Nannong Zizhu’ were compared.The results showed that the average pollen activity of the male parent ’Nannong Hongpingpang’ was 5.5%.The number of pollen attachment on the stigma of’Huangpingpang’ and ’Baipingpang’ was 5.4 and 1.7,respectively,at 24 h after pollination.No obvious pollen tube germination was found.Only mature embryo sac of’Huangpingpang’ was observed on the 8th and 10th day after pollination,but no embryo development was found,and no hybrid seeds were obtained from the two crosses.Therefore,the main reasons for the failure of crossbreeding were the poor development of female parent pistil,few pollen germination on the stigma and the abnormal growth.The results of different pollination treatments showed that:100 mg/L 6-BA>50 mg/L GA>three pollination>CK>100 mg/L NAA>mixed pollination,of which 100 mg/L 6-BA treatment showed the highest seed setting rate,64%higher than the control.The results of fluorescence microscope observation and seed setting rate statistics showed that the number of pollen germination on stigma was directly proportional to the seed setting rate of hybridization.2.’Baipingpang’,’Huangpingpang’ and ’Nannong Huangfengwo’ were used as female parents to produce hybrids via embryo rescue.The results showed that embryo rescue in some crosses could overcome hybrid obstacles and produce hybrid progenies.The suitable medium for embryo rescue was MS+2 mg/L 6-BA+0.75 mg/L NAA for the crosses with’Baipingpang’,’Huangpingpang’ as female parents.As for the embryo rescue time,20～23 d,8～11d and 8 d after pollination were the relatively suitable for the crosses with’Baipingpang’,’Huangpingpang’,and ’Nannong Huangfengwo’ as female parent,respectively.The seedlings obtained by SRAP molecular marker and morphological identification found that all the hybrids yielded by embryo rescue were true hybrids.3.A total of 358 F1 hybrids of pompon type ’Nannong Huangfengwo’×rosette type’Huangju’ were used to investigate the variation of the five flower traits,i.e.,flower diameter,flower height,glossy flower number,tubular flower number and glossy flower length by using the main gene plus polygene mixed genetic model.The results showed that the coefficient of variation of the 5 floral characters ranged from 15.77%to 131.51%,and the geterosis of reached a significant level(P<0.01),and there was the phenomenon of transagressive segregation,among which the flower diameter,the number of lingual flowers,the number of tubular flowers and the length of lingual flowers showed a super-parent heterosis.The results of mixed genetic model analysis showed that the flower diameter,flower height and glossy flower length were in accordance with A-1 model,showing an additive dominant effect controlled by one major gene,while the number of glossy flowers and the number of tubular flowers were in accordance with B-1 model,showing an additive dominant epistatic effect controlled by two major genes,and the heritability of the major gene was 38.96%～49.23%.4.A total of 14 traits,i.e.,plant height,internode length,stem diameter,stem filling degree,leaf length,leaf width,angle of petiole,flower diameter,flower height/flower diameter,ray flowers number,tubular flower number,leaf vase life,flower vase life and disease resistance were selected as evaluation factors.A comprehensive evaluation system of large-flowerd pompon cut chrysanthemum was established by using AHP,and 51 F1 generation plants were preliminarily screened out.The weight value of each character was determined,among which the flower height/diameter showed the greatest influence on the cut flower of pompon type,with the weight value of 0.239,followed by the number of lingual flowers and tubular flowers,with the weight values of 0.154 and 0.114,respectively.Through K-means cluster analysis,51 progenies were divided into 3 grades:8 superior lines,accounting for 15.69%,from which a new variety were named;22 good lines,accounting for 43.14%;21 poor lines,accounting for 41.18%. |
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