Inheritance tendency of fruit traits in the hybrid progenies of Yuluxiang × Akizuki pear

【Objective】The study aimed to investigate the genetic variation of fruit quality traits in the hybrid progeny derived from a cross between Yuluxiang (Pyrus bretschneideri) and Akizuki pear (Pyrus pyrifolia), in order to provide a theoretical reference for pear crossing breeding and parent selection. 【Methods】When the fruits were ripe, 30 pears were randomly picked from each tree of hybrid strain and parental plant from four directions, and 23 descriptive traits such as fruit shape and 13 numerical quality trait indexes such as fruit weight were observed and determined, with three replications for each index. Twenty-three descriptive traits and 13 numerical quality traits were investigated for heritability and correlation analyses using the maternal parent Yuluxiang, the paternal parent Akizuki, and 175 hybrid progeny as materials. Excel 2019 and SPSS 23.0 were used to organize and analyze the data obtained from the investigation, and calculate its mean, standard deviation, kurtosis, skewness and other parameters, to observe the genetic variation. Excel 2019 was used to draw its corresponding frequency distribution histogram, and SPSS 23.0 was used to test for normal distribution and draw a normal distribution Q-Q plot; and to make correlation analysis between traits.【Results】The descriptive traits of 23 fruits showed 92 traits segregation, in which the inheritance of 10 traits, namely, fruit shape, over color,depth of stalk cavity, width of stalk cavity, arris/fossa on fruit surface, attitude of sepals, relief of area around eye basin, flesh texture, amount of stone cells and juiciness of flesh were inclined to the parent Akizuki, and the inheritance of 6 traits, namely, bulge on the base of stalk, degree of fruit skin smoothness, ground colour, dot obviousness, flavor and aroma, was more in favor of the parent Yuluxiang. And the parents performed consistently in 7 traits, namely, attitude of stalk in relation to axis of fruit, persistency of sepals, depth of eye basin, width of eye basin, flesh color, flesh texture type and astringency. The traits of fruit shape and fruit flavor were separated greatly, both appeared 8 kinds of segregation, fruit shape included oblate, globose, long globose, ovate, obovate, conical, cylindrica and spindleshaped, the hybrid progeny were mainly oblate and globose. The hybrid progeny was mainly sweet and light sweet. The coefficients of variation for the 13 numerical quality traits ranged from 6.28% (fruit shape index) to 46.69% (titratable acid content), the heritability ranged from 49.18% (Single fruit mass) to 241.26% (flesh firmness), and the heterosis rate ranged from -50.82% (Single fruit mass) to 141.26% (flesh firmness), in which flesh firmness had the highest heritability and positive dominance rate, the strongest additive effect, and outstanding hybrid dominance, which could improve fruit storability to a certain extent, while fruit weight had the lowest heritability and dominance rate, which was highly subjected to the influence of environmental conditions. In addition, the fruit weight, fruit length and fruit diameter showed obvious degeneration and tended to be low heritability, while the mean values of flesh firmness and fruit stalk length were higher than the median value of parents and tended to be high heritability, and the long fruit stalk of Yuluxiang was more likely to inherite to the progeny. The mean values of the stalk thickness and fruit shape index were lower than the median value of the parents, which tended to be less heritable, and the fruit shape was greatly influenced by the parent Yuluxiang. The mean values of titratable acid content were slightly larger than the median value of the parents, but the ratio of those below the low values was much greater than that above the high values, showing a general tendency towards low heritability, and were significantly influenced by the parental Yuluxiang. The soluble sugar content, soluble solids content, solid-acid ratio and sugar-acid ratio were greatly influenced by the parent Akizuki, and the soluble sugar content and soluble solids content tended to be inherited in a high degree, while the titratable acid content, solid-acid ratio and sugar-acid ratio tended to be inherited in a low degree.【Conclusion】The 23 fruit descriptive traits showed different degrees of variation. Among the 13 numerical quality traits, 9 traits such as fruit length and fruit diameter conformed to normal distribution, and the fruit weight, titratable acid content, sugar-acid ratio and solid-acid ratio were skewed. The fruit weight, fruit length, fruit diameter, core size, fruit shape index, flesh firmness, stalk length, stalk thickness, titratable acid content, soluble solids content, solid- acid ratio, sugar- acid ratio and soluble sugar content were characterized by the inheritance of quantitative traits, and there was trait segregation with different degrees. This experiment would provide a basis for breeding new varieties.