Optimizing Of Fruit Traits Evaluation Method For "Large Population" Hybrid Progenies Of Apple

There are many ways to select new varieties of apple?Malus domestica Borkh.?,among which cross breeding is the most effective method.At present,the breeding strategy of“less combination and larger group”is widely used in breeding research,and the apple breeding group is generally larger.Compared with the small group,the workload of the large group of breeding has increased several times,and the evaluation of fruit traits in the re-selection stage is the most difficult.In order to improve the efficiency of breeding research,this study selected parts of the four cross combinations of‘Fuji'בGala',‘Fuji'בGolden Delicious',‘Fuji'בQinguan'and‘Fuji'בCripps Pink'the progeny of the cross are test materials.From August to November in 2018 and 2019,a combination of sensory evaluation and instrumental measurement was used to evaluate the fruit quality traits during the re-selection process.According to the three-level selection and elimination method to determine the evaluation index,the individual hybrid offsprings are eliminated in batches,and the elimination rate is counted.The aim is to simplify the evaluation indexes of fruit traits and optimize the evaluation methods of fruit traits,so as to provide a basis for simplifying the cross-breeding procedure of apple“large group”and improving the selection efficiency.The main research results obtained are as follows:1. Sensory evaluation and measurement analysis of fruit appearance traits and intrinsic quality traits of the F₁ generation of four hybrid combinations were perform.The results showed that the sensory indicators such as fruit shape,color,fruit rust,flesh texture,flesh roughness,juiciness etc.were widely separated in the hybrid offspring of the four combinations.Physical and chemical indexes,such as weight of single fruit,soluble solid and flesh hardness,all showed a distribution state of less at both ends and more at the middle in the hybrid offspring of the four combinations,which is a quantitative trait of continuous variation of phenotype,but the color does not conform to the genetic characteristics of quantitative traits.During the two consecutive years of investigation,the genetic variation of each trait was stable.2. Optimization of fruit character evaluation methods.The evaluation indicators were sorted and analyzed,and a three-level evaluation system for fruit traits was established:the primary evaluation used fruit rust and off-flavor as evaluation indicators,and the plants with obvious defects are mainly eliminated;the secondary evaluation used smoothness,coloring degree,texture,flavor as an evaluation index,aroma is used as an auxiliary selection index to eliminate plants with poor performance of the main quality traits of the fruit;the tertiary evaluation is mainly focuses on comprehensive sensory evaluation,and combines two physical and chemical indicators of pulp hardness and soluble solids.The best lines are compared with the same maturity period.3. The threshold of the selection rate of cross generation was set at 95%.Using the survey data of fruit traits of hybrid offspring in 2018 and 2019,the rationality of the evaluation index and the feasibility of the grading evaluation method were verified.The results showed that after the selection and evaluation by the“staircase”classification,the hybrid single plants of four combinations of‘Fuji'בGala',‘Fuji'בGolden Delicious',‘Fuji'בQinguan'and‘Fuji'בCripps Pink'can be eliminated by 96.94%,98.39%,99.56%and 95.74%,respectively.