Effects of tree shape on canopy structure, photosynthetic characteristics and fruit quality of early cultivated nectarine

Abstract:【Objective】Choosing a good tree shape and improve the light distribution in the inner canopy is a common concern of researchers. It is necessary to explore the tree shape with high light efficiency and labor saving. This study examined the effects of different tree shapes on canopy structure and fruit quality of peach cultivated for early production, so as to select suitable tree shapes with high photosynthetic efficiency and labor saving.【Methods】Zhongnong Zaozhenzhu is a new early nectarine variety bred from the offspring of Autumn Red Pearl, which is suitable for cultivation in open fields and greenhouses in Huludao and the south area of Liaoning province. The Zhongnong Zaozhenzhu nectarine was taken as the test material, and it was a 4-year container cultivated seeding. The relative light intensity, canopy structure, diurnal variation of photosynthesis and fruit quality were studied in trees with different tree shape including central leader shape (CL), guyot trellis (GT), opposite V shape (OV), and tatura V trellis (TV).【Results】The tree shapes with the average relative light intensity from high to low were OV, TV, GT and CL. The ratio of effective light region in OV was the largest, which was 77.73%. The canopy area with relative light intensity lower than 40% was regarded as low light efficien-cy area. The proportion of low light efficiency area in OV and GT was significantly lower than that in TV and CL and was 10.75% and 6.10%, respectively, compared with CL. There was a positive correlation between total gap fraction and openness. The total gap fraction and openness of CL and GT were significantly higher than those of OV and TV. Among them, the total gap fraction and openness of the canopy in GT were the largest, 36.21% and 38.09%, respectively. Those in TV were the smallest, being 11.10% and 11.43%, respectively. The trend of leaf area index was opposite to that of total gap fraction and openness. The leaf area index of OV and TV was significantly higher than that of CL and GT. Among the four tree types, OV had the highest light interception rate and daily net photosynthetic accumulation of the leaves, which were 92.70% and 1 768.97 mmol· m- 2 respectively. In the upper, middle and lower layers of the canopy, the single fruit weight in OV was significantly higher than that of the other tree shapes. The content of soluble solids in fruit of the upper and middle canopy in OV was significantly higher than that in the other tree shapes. The content of soluble solids content in the lower layer of TV was significantly higher than that in other tree shapes. The titrable acid content in upper and middle canopy fruit in OV was significantly higher than that in the other tree shapes. No lactones were detected in CL and GT. The highest content of lactones was detected in OV (52.42 ng·g^-1 ). The content of esters detected in OV was 8.6 times and 10.1 times of that in CL and GT, respectively. The content of esters detected in TV was 4.7 times and 5.5 times of that in CL and GT, respectively. The contents of esters and lactones were higher in OV and TV. The content of linalool with flower-like aroma was higher in OV and TV.【Conclusion】Principal component analysis was carried out on the 11 indicators of 4 tree shapes, and 3 principal components were extracted. The cumulative variance contribution rate reached 87.759%, and the corresponding variance contribution rate was 61.899%, 16.269% and 9.591% respectively, which basically represented the majority of information of all indicators. The 11 indexes were thus selected for principal component analysis. The results showed that the score in the order from high to low was OV＞TV＞CL＞GT. The opposite V shape had the highest comprehensive score and the fruit quality was the best. It is an excellent tree shape for promoting early cultivation of early nectarine varieties.