Genetic Diversity Evaluation Of Natural Pollinated Progeny And Selection Of Excellent Strains Of Ornamental Crabapple

In order to investigate the genetic diversity of the natural pollinated progeny of North American Begonia,and to screen the superior offspring with good fruit viewing effect in winter and strong cold resistance.In this study,we used the mother tree of 4 North American begonia varieties and their natural pollinated progeny of 4 years as materials.The pollination characteristics of the mother tree,as well as the phenotype,cold resistance,molecular level of the offspring were studied.The results were as follows:The apomictic reproductive ability was represented by the seed setting rate of emasculation without pollination.The results suggested that all 4 North American begonia varieties had the capacity.The sequence from strong to weak was No.7 North American begonia,No.2 North American begonia,No.10 North American begonia and No.9 North American begonia.Under natural pollination conditions,the rate of apomixis was significantly lower than that of emasculation without pollination.Further study was needed to explain the mechanism of this phenomenon.The investigation on natural pollinated progeny’s qualitative traits showed that the progeny groups had richer types than the mother trees in each trait.The variation coefficients of quantitative traits ranged from 8.45% to 89.77%,among which the single fruit weight was maximum in 4 genealogies.Differences among individual plants in four progeny populations of each trait reached a significant level,which indicated abundant genetic diversity.Principal component analysis showed that fruit size,leaf blade size and petiole length were more prone to genetic variation in progeny populations.The genetic diversity of 4 natural pollinated progeny of North American Begonia changed from 0.3515 to 0.3763,the heterozygosity ranged from 0.7025 to 0.7496.The progeny populations of No.2 North American begonia’s average genetic diversity information content was 0.2811,progeny populations of No.7 North American begonia’s average genetic diversity information content was 0.2780,progeny populations of No.9 North American begonia’s was 0.2635,and progeny populations of No.10 North American begonia’s was 0.2848,who showed abundant genetic diversity in phenotype and molecule aspect.Variance analysis of molecular genetic diversity suggested,natural pollinated progeny had a richer genetic diversity than hybrid progeny,whose differences reached extremely significant levels.Comparatively speaking,natural pollinated progeny had higher genetic diversity,and had greater potential for selection and utilization among individual plants within the family.A comprehensive study on the hardness index,shrinkage and discoloration of fruits under different low temperature treatment showed that among the four ornamental begonia progeny plants,the irreversible temperatures of fruit cold damage were all below-20℃,part of them could below-30℃.Special No.3 plant of No.2 North American begonia’s offspring and the antifreeze plant of No.7 North American begonia’s offspring,whose fruit were bright red.No.73 B plant and special No.1 plant of No.7 North American begonia’s offspring,their fruit respectively were yellow and orange.No.28 plant and No.49 plant of No.2 North American begonia’s offspring,their fruit didn’t change significantly under temperature stress of-40℃,which showed strong resistance to cold.All the plants referred above were hybrid plant,had the prospect of promotion and application.