Genetic diversity,population structure,and relationships of apricot(Prunus)based on restriction site-associated DNA sequencing

Single-nucleotide polymorphisms(SNPs)are the most abundant form of genomic polymorphisms and are widely used in population genetics research.Here,high-throughput sequencing was used to examine the genome-level diversity,population structure,and relationships of apricot,which are important for germplasm conservation and molecular breeding.Restriction site-associated DNA sequencing(RAD-seq)was adopted to sequence 168 Prunus spp.accessions distributed in five ecological groups,including 74 accessions of cultivated Prunus armeniaca L.and 94 accessions of wild apricots(P.armeniaca L.and Prunus sibirica L.),which generated 417,961 high-quality SNPs.We used cluster,genetic structure,and principal component analyses to examine the genetic diversities and genetic relationships of the 168 accessions.The Dzhungar-Ili ecological group accessions showed the highest genetic diversity in terms of private allele number,observed heterozygosity,and nucleotide diversity.We speculate that the Central Asian ecological group accessions were domesticated from the Dzhungar-Ili ecological group accessions.The population structure and gene flow of the North China and European ecological group accessions suggested a genetic background of P.sibirica.We argue that the two groups should be considered hybrid swarms connected to P.sibirica by continuous and extensive gene flow.P.armeniaca originated in Northwest China(Ili Valley),subsequently spread throughout Central Asia,and eventually spread to Europe.In addition,selective sweep signatures in P.armeniaca during domestication from wild to cultivated apricots,combined with differentially expressed genes,underlie distinct fruit traits,including sugars,aromas,organic acids,and carotenoids.This study provides substantive and valuable genomic resources that will significantly advance apricot improvement and effective utilization.

Self-incompatibility Characteristics of 34 Apricot Cultivars in Xinjiang

[ Objective] This study aimed to explore the relationship between self-incompatibility strength and characteristics related to pollination and fertilization of different apricot varieties in Xinjiang. [ Method] The pollen amount, pollen germination rate, pollen tube growth status and fruiting setting rate by self-pollina- tion of 34 apricot cultivars in Xinjiang were determined, to analyze the self-incompatibility of different apricot cultivars. [ Result] The average pollen amount per anther of 34 apricot eultivars was 1 213.7, and the average pollen germination rate was 46.0%. There were great differences in the self-incompatlbility of different cuhivars ; most pollen tubes of the euhivars with high self-incompatibility stopped elongating at 1/3 or 1/2 part of the styles, and only a few pollen tubes of the euhivars with low self-incompatibility reached the ovary, and the normal fertilization ratio was significantly lower than that in self-compatible cultivars. [ Conclusion] Among the 34 apricot cuhivars, only 6 cuhivars were self-compatible and the others exhibited gametophyte self-incompatibility. In addition, the fruit setting rate by self-pollination was low.

Study on Dynamic Characteristics of the Growth and Development of Armeniaca dasycarpa(Ehrh.) Borkh

[ Objective] This study aimed to analyze the dynamics of growth and development of Armeniaca dasycarpa （ Ehrh. ） Borkh fruit, thus providing the the- oretical basis for cultivation and breeding of good-quality and high-yield A. dasycarpa. [ Method] With A. dasycarpa cultivar Yechengzixing as the experimental material, P. cerasifera Ehrh cultivar Huangguoyingtaoli and A. vulgaris Lam. cultivars Luopuhongdaike, Wanshujianali and Kuchetuoyong as control, the vertical diameter, horizontal diameter and fresh weight of fruit and embryos were measured every 7 d during the growth and development period. [ Result] The result showed that the whole fruit growth period of Yechengzixing, lasted 93 d from the end of flowering to fruit maturity. The dynamics of fruit vertical diameter, horizon- tal diameter and fresh weight of Yechengzixing presented ＂rapid-slow-rapid＂ double S-shaped curves. The whole fruit growth period of Yechengzixing could be di- vided approximately into three stages： first rapid growth stage, slow growth stage and second rapid growth stage, which lasted 29, 42 and 21 d, respectively. Daily increment of fruit vertical diameter and horizontal diameter of Yechengzixing reached the maximum at the first rapid growth stage, while daily increment of fruit fresh weight reached the maximum at the second rapid growth stage. The dynamics of vertical diameter, horizontal diameter and fresh weight of Yechengzixing embryos presented S-shaped curves. Fruit growth and development dynamics of the tested materials presented double S-shaped curves. The whole fruit growth period of Yechengzixing, Huangguoyingtaoli and three apricot cuhivars lasted 93, 119 and 77 -98 d, respectively. Thus, the duration of fruit growth period of Yechengzixing was 26 d shorter than that of Huangguoyingtaoli and exhibited no significant difference compared with three apricot cultivars. The duration of each growth stage and daily increment of Yechengzixing fruit had no significant difference compared with three apricot cultivars. Moreover, Huangguoyingtaoli had a longer slow growth stage and lower daily increment than Yechengzixing. [ Conclusion] The whole fruit growth period, duration of each growth stage and daily increment of Yechengzix- ing exhibited no significant difference compared with three apricot cultivars but varied remarkably compared with Huangguoyingtaoli.