Genetic Analysis Of Major Fruit Traits In The Hybrid Offspring Of Citrus ’Hongmeiren’ And Screening For The Superior Early-maturing Varieties

The fundamental task of citrus breeding is to breed excellent new varieties,Cross breeding can directionally breed superior varieties with complementary parental traits or super-parental.Fruit quality is always regarded as the first breeding goal in citrus hybrid breeding,and good fruit quality should have the characteristics of deliciousness,good-looking and convenient at the same time.The maturity period is also an extremely important breeding goal,especially the selection of early-maturing varieties.In this experiment,middle-maturing‘Hongmeiren’was used as the female parent,and 308 F₁generations crossed with the early-maturing male parent‘Jinqiu Shatangju’,88 F₁generations crossed with the middle-maturing male parent‘Chenggu Bingtangju’,and202 F₁ generations crossed with the late-maturing male parent‘Chunjian’as the test materials.From the year 2018 to 2020,observed the main fruit characteristics of the three hybrid combinations.The normal distribution figure was used to reflect the distribution variation of the main traits of the hybrid offspring,analyzed its genetic law,and use a variety of evaluation methods to comprehensively evaluate and rank the early-maturing offspring of each hybrid combination.The purpose was to explore the genetic law of fruit traits in the offspring of the three combinations of the femal parent of‘Hongmei’,and to screen out excellent early-maturing plants or hybrid parent materials.The main research results are as follows:1 Distribution of main fruit traits of hybrid offspringsAmong the 10 quantitative traits of hybrid progeny,the coefficient of variation of single fruit weight,peel thickness,TA,TSS/TA,and seed number were all above 0.30,and the progeny has a greater segregation of traits.The progeny of the three hybrid combinations were separated as early maturity,medium maturity and late maturity.The overall maturity stage showed the prone to middle maturity.The progenies of‘Hongmeiren’x‘Jinqiu Shatangju’were mainly early maturing single plant（146～190 d）,accounting for 53.25%;The progenies of the cross of‘Hongmeiren’x‘Chenggu Bingtangju’mainly matured at medium maturity（191～250 d）,accounting for 61.36%.The medium maturity of the cross progeny of‘Hongmeiren’x‘Chunjian’was 68.81%The single fruit weight,longitudinal diameter,transverse diameter and fruit shape index of the hybrid offspring showed continuous variation,which belonged to the genetic characteristics of quantitative traits controlled by multiple genes.The coefficient of variation of single fruit weight traits was the largest compared with the longitudinal diameter,transverse diameter and the fruit shape index,ranging from 0.39 to 0.51.Among them,the coefficient of variation of the single fruit weight,the longitudinal diameter,the transverse diameter and the shape index of the‘Hongmeiren’x‘Chunjian’F₁ generation were the largest.The hybrid progeny of‘Hongmeiren’x‘Jinqiu Shatangju’were mainly medium and small fruit types,and the fruit shape is mainly high oblate round;the hybrid progeny of‘Hongmeiren’x‘Chenggu Bingtangju’were mainly medium fruit type,and the fruit shape is mainly high flat round and round or nearly round.The hybrid offspring of‘Hongmeiren’x‘Chunjian’combination were mainly large to extremely large fruit type,and the fruit shapes were mainly round or nearly round and oval.The peel color of hybrid offspring of‘Hongmeiren’x‘Jinqiu Shatangju’yellow:orange-yellow:orange-red:deep red=10:63:29:1,That of‘Hongmeiren’x‘Chenggu Bingtangju’yellow:orange-yellow:orange-red=1:16:12,That of‘Hongmeiren’x‘Chunjian’yellow:orange-yellow:orange-red:deep red=4:62:35:1.Three hybrid combinations were mostly orange-yellow progeny.And were mainly medium peel thickness.The TSS of the three hybrid combinations was mostly below 12%,while the offspring of more than 12%were part but less;TA is mostly distributed in 0.41～0.80%;TSS/TA was mostly in two-peak or three-peak distribution,and 18.01～30.00 were relatively more distributed.The fruit pulp flavor variation of the hybrid offspring was very wide,ranging from sour,slightly sour,sour-sweet,slightly sweet,and sweet.The hybrid offspring of‘Hongmeiren’x‘Jinqiu Shatangju’and‘Hongmeiren’x‘Chenggu Bingtangju’were mainly sour and slightly sour,and followed by the sweet and sour flavor.The‘Hongmeiren’x‘Chunjian’combination was mainly sweet and sour,followed by the sour and slightly sour flavor.In the descendants of each combination,relatively masticatory accounts for the vast majority,followed by non-masticatory.and polarized masticatory was the least.‘Hongmeiren’x‘Jinqiu Shatangju’F₁seedless strains accounted for 17.86%,less nucleus strains accounted for 33.77%,medium number nucleus strains accounted for28.57%:multi-nucleus Strains accounted for 19.81%.The F₁ generation seedless strains of‘Hongmeiren’x‘Chenggu Bingtangju’accounted for 6.82%,less nuclear strains accounted for 18.18%,medium number nucleus strains accounted for 43.18%,and multi-nucleus strains accounted for 31.82%.‘Hongmeiren’x‘Chunjian’F₁ generation seedless strains accounted for 26.73%,less nuclear strains accounted for 37.62%,medium number nucleus strains accounted for 22.77%and multi-nucleus strains accounted for 12.87%.2 Inheritance of main fruit traits of hybrid offspringsThe average F₁ values of maturity days for the three hybrid combinations were close to the mid-parent value,and the maturity period is mid-mature,indicating that the maturity period of most hybrid offspring tended to mid-parent,and the heritability of each combination is above 0.80,which was affected by the addition of genes effect.The progeny of the three combinations had a higher inferior-low parental rate than its super-high parental rate,and the proportion of maturity days less than that of the lower parent was more,and it was more inclined to the inheritance of the parents in the early maturity period.It can be seen that if you want to get more early-maturing offspring,one of the parents must be an early-maturing line or choose crosses in which the maturity period of the two parents differs greatly.The average value of F₁ of single fruit weight,longitudinal diameter,transverse diameter in each combination were lower than the middle parent value,and the inferior-low parental rate were high,and there was a decreasing trend.Similarly,the TSS,TA,and TSS/TA of the hybrid offspring also had a significant tendency to deteriorate.The average content of TSS and TSS/TA in the two combinations with‘Jinqiusha Tangju’and‘Chenggu Bingtangju’as the male parent was less than the middle parent value,The inferior-low parental rate was also much higher than its ultra-high parental rate,the average TA content was higher than the middle parental value,and the ultra-high parental rate was higher.The average TSS content of the combination with‘Chunjian’as the male parent was lower than the middle parent value,and TA and TSS/TA were close to the middle parent value.Correspondingly,the overall flavor and masticatory properties of the hybrid offspring were also weaker than that of their parents,and the average F₁ score of each combination was lower than the middle parent value,and the inferior-low parental rate were high.The F₁ generation peel color score of each combination was close to the middle parent value.The orange-yellow progeny of the three cross combinations account for the majority,which was more inherited from the female parent.If you want to cultivate varieties with red peel,it is best to choose red varieties as the female parent.The heritability of the peel color scores of the three combinations was low,ranging from0.28 to 0.34,indicating that the peel color was less affected by the additive effect of genes,and may be more affected by the dominant and epistatic effects of genes.The average value of F₁ of the seed numbers of the three hybrid offsprings were all greater than the middle parent value,and the ultra-high parent rate was much higher than its inferior-low parental rate,and the number of seeds tended to increase.Seed number traits were more inclined to inheritance from the male parent.If you want to breed a larger number of seedless parents,it is recommended to choose seedless parents for crossbreeding,especially select the seedless male parent is more important.3 Screening of superior early-maturing varietiesUse Principal Components Analysis and Cluster Analysis to simplify the fruit traits into 4 core evaluation indicators,combine the Analytic Hierarchy Process and Technique for Order Preferenceby Similarity to Ideal Solution method to calculate the comprehensive scores of the offspring of the early maturity hybrids of the three combinations,and screen the top two of each strains were selected as excellent strains,finally selected Zhong10-4-5,Nan12-6-12,Nan29-1-4,Nan29-1-2,1Zhong20-7-5 and2Zhong21-4-8,there are 6 excellent plants in total,and the comprehensive quality is consistent with the actual observation results.