| The genetic background of citrus is ich and colorful,and there is no reproductive isolation in interspecific hybridization or even intergeneric hybridization.The key to the success of hybrid breeding lies in the selection of parents.Therefore,it is necessary to identify and evaluate the F1 generation population of the hybrid combination summarize and analyze the inheritance of hybrid offspring.It is an indispensable work to lay a foundation for the targeted selection of high-quality individual plants that meet the breeding goals in the future and also to accumulate materials for big data breeding based on modern molecular biology.In citrus breeding,seedless or less seed is the focus and hotspot of citrus variety breeding,and it is one of the commercialized breeding goals.Based on years of observation and determination,the following four hybrid combinations were selected for this experiment: ’Ehime 28’ × ’Chunjian’,’Ehime 28’× ’ W·Murcott ’,’Ehime 28’ × ’ No.3Ponkan ’ and ’Ehime 30’ × ’Chunjian’,The main fruit traits of the hybrid progeny of the above four combinations were observed and measured for three consecutive years from2019 to 2021,and their genetic variation laws was analyzed nd then the comprehensive evaluation on seedless lines were carried out.The purpose of this experiment is to explore the inheritance law of the main characters of the F1 generation of the four hybrid combinations,select a batch of parent materials with an excellent performance from the hybrid F1 generation to provide innovative germplasm resources and data support for subsequent hybrid breeding.At the same time,a number of seedless superior plants with excellent fruit quality will be screened as potential new variety resources.The experimental results are as follows:1.Distribution of basic traits and genetic variation of F1 generation fruitsIn terms of fruit weight,the average fruit weight and fruit shape index of the F1 generation were quantitative traits controlled by multiple genes.In terms of individual fruit weight distribution,each F1 generation had small fruit,medium fruit and large fruit,and all four combinations were dominated by medium fruit,with very small or very large fruit accounting for a relatively small percentage.In terms of heredity,the heritability was greater than 0.85 and was little affected by the environment.The average value of the F1 generation of each combination was less than the median parental value,and the inferiorlow parental rate is greater than the ultra-high parental rate.The overall heritability showed a decreasing trend.In terms of fruit shape,the heritability of the four combinations is above 0.9.The F1 generations of ’Ehime 28’ × ’Chunjian’ are mainly round,while the F1 generation of the remaining three combinations had mainly tall flat round fruits.The three combinations with ’Ehime 28’ as the female parent,showed that in the case of the same female parent,the fruit shape index of the male parent is about large,and the average value of the fruit shape index of the F1 generation also increased.The distribution range of TSS in the four combinations was not much different.The TSS of most lines was less than 11.0%,but some high-sugar plants appeared.The heritability of TSS in the four combinations ranged from 0.39 to 0.78.The ultra-high parental rate was much smaller than the inferior-low parental rate.And the median parental value was also greater than the mean of F1.The heritability of TSS showed a decreasing trend.The heritability of TA is above 0.85.the first three combinations of F1 mean value were greater than the median parent value,showing an overall upward trend of inheritance.The solid acid ratio of most lins is concentrated in 12.00～22.00,the heritability is above 0.9,and the median parent value is greater than the average value of F1 and combined with the genetic performance of TSS and TA,the solid acid ratio also showed a genetic trend of deterioration.The pulp flavors of the five parents of the four crosses was sweet or sour,while in the F1 generation,sour,sour,sour-sweet,sweet and sweet all appeared,and the characters were widely separated.Among them,the hybrid progeny of ’Ehime 30’ × ’Chunjian’ has the most sour-flavor strains,while the other three combinations had the most sour-sweet.In terms of heredity,the heritability of the four combinations is between 0.47 and 0.86.Due to the deterioration of citrus in sugar and acid,the evaluation of the pulp flavor of the F1 generations is not as good as that of its parents,with a lower score and a tendency to deteriorate.In the distribution of slagging properties of the four combinations,the slagslagging strains accounted for the majority in their respective combinations.For the evaluation of slagging,the heritability is between 0.49 and 0.71,and the average score of the F1 generation is smaller than that of its parents,which also shows deterioration in inheritance.Pericarp hardness and thickness are also quantitative traits controlled by multiple genes.Most of the pericarp hardness is between 1.500 kgf and 2.500 kgf.The heritability of the four combinations is above 0.8,and the ultra-high parental rate was greater than the ultra-low parental rate,with a tendency to increase.In terms of peel thickness,most of the lines of the four combinations are distributed between 1.00 mm and 3.00 mm,From the genetic point of view,the heritability of the four cross combinations is between 0.60 and 0.96.The average value of F1 generation is smaller than the median parent value of their respective combinations,and the thickness tends to decrease.The variation of peel color is also very wide,ranging from light yellow to dark red,with the largest number of progenies from the four crosses being orange-yellow and very few strains with dark red pericarp color.Genetically,there is a certain correlation between the pericarp color depth of the F1 hybrid offspring and the paternal pericarp color.The redder the paternal pericarp color,the redder the hybrid offspring pericarp color.The distribution range of juicing rate is 13.38%～71.01%,and most of the lines are distributed between 50～60%,showing a continuous variation,a large variation range,The average juicing rate of the F1 generation of the four combinations is less than the middle parent value of their respective combination,and the inferior-low parent rate of all four combinations are greater than the ultra-high parent rate,The juice yield tended to decrease heredity,and the heritability is between 0.86 and 0.92,indicating that heredity is not easily affected by the environment and is relatively stable.The performance of Vc content in the four hybrid offspring is different.From the distribution point of view,the maximum and minimum values are also different.The minimum content is only 13.38%,while the highest content reaches 65.54%.The three combinations with ’Ehime 28’ as the parent were mainly concentrated between 20 and 35mg/100 ml.The hybrid progeny of ’Ehime 30’ × ’Chunjian’ mainly concentrated in the range of 30-50 mg/100 ml.From the perspective of genetic analysis,the heritability of the four combinations is above 0.9,and each combination showed different genetic trends,so the overall trend could not be judged.In terms of seed number,the percentage of seedless or less nuclear strains in the progeny of ’Ehime 28’ × ’Chunjian’ cross was 72.58%,the percentage of seedless or less nuclear strains in the progeny of ’Ehime 28’ × ’ No.3 Ponkan’ cross progeny had 40.00%of nucleus or less nucleus,’Ehime 28’ × ’W-Mercote’ cross progeny had 53.96% of nucleus or less nucleus strains.The percentage of kernelless strains in the progeny of ’Ehime 30’× ’Chunjian’ cross was as high as 66.21%.The heritability of all four combinations is above 0.9.The average number of seeds in the hybrid progeny of the three crosses with’Ehime 28’ as the parent was less than the middle parent value,and the ultra-high parent rate was greater than the inferior-low parent rate,and the number of seeds tended to increase.It was also found that the number of seeds in the F1 generation increases with the increase of the number of seeds of the male parent.Therefore,the seedless male parent is the best choice for breeding new seedless varieties.in the breeding process.2.Screening of seedless superior strainsSix core indexes were screened out by principal component analysis and cluster analysis,and the comprehensive score of F1 generation seedless single plant was calculated by analytic hierarchy process(AHP)and the distance between superior and inferior solutions.The top 10 lines with comprehensive scores are selected as the seedless superior plants: 9-7-1 in 2,10-1-2 in 1,20-1-3 in 2,20-5-9 in 2,1-1-8 in 1,3-1-12 in 1,9-2-9 in 1,3-4-6 in 2,9-2-12 in 2,10-1-2 in 2..The main characters of the above lines basically meet the requirements of citrus quality,and will be regarded as the key lines for the next generation of clonal M1 and M2 generation cultivation and further observation,identification,and evaluation. |
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