| Peach(Prunus persica L. Batsch) originated in China and its shape can be divided into round(the round peach) and flat(the flat peach) type.Flat peaches were favored by consumers because of its flat shape, edible convenience and unique sweet flavor. The flat peaches always contain higher sugar content results from pleiotropism of flat gene which is also considered as an important breeding approach. To date, no reliable molecular markers can be used in flat peach marker-assisted selection(MAS) breeding.The molecular and physiological mechanism of flat peach development remains unknown. Here we focus on investigating the physiological mechanism of the flat peach shape formation preliminarily and exploring the fruit shape gene subsequently. With these results, we can develop the molecular markers for flat peach breeding to enhance the breeding efficiency and clarify the molecular mechanism of the unique fruit shape.Firstly, the physiological factors that result in different fruit shape were analyzed by measuring fruit endogenous hormone levels between round and flat peaches. Meanwhile, to identify the flat gene, we analyzed the sequences and the relative expression levels of a 50 kb candidate region which was determined by genome-wide association study(GWAS). Through these experiments, we are trying to confirm the flat gene and investigate the physiciolgical mechanism of the formation of flat fruit shape. The main results are as follows:1. Endogenous hormone conten between different fruit shape: To investigate the effects of four main endogenous hormones on fruit shape development, we measured the content of hormones in different parts of fruit and different cultivars. The data show that the content of IAA and GA4 in round peaches were significantly higher than that of flat ones, while there was no significant difference in the content of ZR and GA3 between round and flat peaches. Furthermore, the content of GA4 on the top of fruit was significantly higher than the middle part in all three round peach cultivars. Compared to all of the four hormones, IAA keeps a higher level during fruit development. This experiment priminarily show that IAA and GA4 played important roles in the development of fruit shape.2. Determination of SNP associated with fruit shape: The candiate region was determined by GWAS. The most associated SNP was Chr6: 25060196(Prunus_persica_v1.0) in peach genome. We then verified the accuracy of the association using another 106 peach cultivars(including 15 flat peaches and 91 round peaches). It showed that the genotype of all flat shape peach was A/T or T/T and all round peaches was A/A. The aborting flat peach is T/T. Our result provided a SNP marker closely associated with fruit shape.3. Development of molecular marker for fruit shape: We develop an useful AS-PCR marker of fruit shape for MAS breeding using the most associated SNP. We can easily and accurately characterize the two different fruit shape through a simple PCR and aragose gel electrophoresis. To further verify the accuracy of this marker, we identified the fruit shape of a F1 population of ’Dajiubao’ × ’Youpantao1-3’ use this marker without any mistakes. Thus, this molecular marker can used in future peach breeding.4. We detected the relative expression of all 13 genes located at 50 kb candidate region in flesh at different fruit develop period. The relative expression levels of Ppa003772 m in round peaches were higher than those in flat peaches during mature period, while they had adverse patterns during fruit development. During fruit development period, the Ppa003772 m was highly expressed in round peach at the later period of development, while it was highly expressed at the earlier period in flat ones. We found that Ppa020486 m was expressed in flower and its relative expression level of round peach was higher than flat ones, while the others were not coincided with its phenotype. Our results indicate that Ppa003772 m and Ppa020486 m might control the peach fruit shape. |
PDF Full Text Request