Abstract: 【Objective】 To establish a comprehensive evaluation model for the selection of superior rootstocks of ‘Shatang mandarin’ by jointly analyzing the plant height, fruit yield and fruit quality of ‘Shatang mandarin’ on different rootstocks under screen house cultivation, so as to provide a basis for the selection of grafting rootstocks of ‘Shatang mandarin’. 【Methods】 Ten different rootstocks were used to graft ‘Shatang mandarin’, and the difference significance analysis and correlation analysis were carried out on 22 indexes of plant height, fruits weight per plant and fruit internal and external quality after fruit bearing, and the differences and correlations among plant height, fruits weight per plant and fruit quality after grafting on different rootstocks were discussed. Finally, the 22 indexes were analyzed by principal component analysis to obtain the core indexes for the screening of ‘Shatang mandarin’ rootstocks, and a comprehensive evaluation model was constructed to screen the excellent rootstocks based on the joint analysis of plant height, fruits weight per plant and fruit quality of ‘Shatang mandarin’. 【Results】 The results showed that there were significant differences in plant height, fruits weight per plant and fruit internal and external quality among the ten citrus rootstocks grafted with ‘Shatang mandarin’, among which the plant height of ‘Sour pummelo’ was not significantly different from the plant height of ‘Shatang mandarin’, while the plant height of ‘Flying dragon trifoliate orange’ was significantly different from the plant height of ‘Shatang mandarin’. It was the shortest rootstock among the 10 rootstocks, and the average plant height was reduced by 50.79% compared with ‘Shatang mandarin’, which also showed that the dwarfing effect of ‘Flying dragon trifoliate orange’ rootstocks was the best among the rootstocks tested. In the results of soil and plant analyzer development (SPAD) value, it could be seen that ‘Flying dragon trifoliate orange’ rootstocks with the best dwarfing effect had the highest SPAD value, reaching 71.92, while ‘Shatang mandarin’ had the highest plant height. On the contrary, the SPAD value was the lowest, is 59.44, and the SPAD values of other rootstocks were higher than that of ‘Shatang mandarin’, which indicated that there was a certain correlation between plant height and SPAD value. Grafting ‘Shatang mandarin’ on different rootstocks will affect the fruits weight per plant. Excluding the interference of other factors, under the unified production management, the fruits weight per plant of ‘Shatang mandarin’ with ‘Goutou sour orange’ rootstocks is the highest. Different rootstocks had different effects on 19 indexes of fruit quality of ‘Shatang mandarin’. The single fruit weight and pulp weight of ‘Xiangcheng’ and ‘Red limonia’ were higher than the other 8 rootstocks, while the single fruit weight and pulp weight of ‘Goutou sour orange’ were the lowest among the 10 rootstocks. Based on the single fruit weight, pulp weight, fruit diameter, fruit volume and fruit shape index, the fruit of ‘Xiangcheng’ rootstocks and ‘Red limonia’ rootstocks were bigger, and the shape was round or nearly round, while the fruit of ‘Goutou sour orange’ rootstocks was the smallest, and the shape was oval or conical. Different rootstocks had different effects on the pericarp characteristics of ‘Shatang mandarin’. From the color of the pericarp, the fruits with rootstocks all showed shiny orange, but the fruit surface color of ‘Xiangcheng’ rootstocks was lighter. Of the 10 rootstocks, ‘Shatang mandarin’ rootstocks had the highest soluble solids content, and ‘Xiangcheng’ rootstocks had the lowest soluble solids content. The results showed that the soluble solids content of ‘Shatang mandarin’ fruit grafted on the other 9 rootstocks was lower than that of ‘Shatang mandarin’ rootstocks. Similarly, among the 10 rootstocks, the titratable acid content of ‘Shatang mandarin’ rootstocks was the highest, and the titratable acid content of ‘Goutou sour orange’ rootstocks, ‘Flying dragon trifoliate orange’ rootstocks and ‘Rough lemon’ rootstocks was the lowest. Compared with ‘Shatang mandarin’ rootstocks, the titratable acid content of the fruits of the other 9 rootstocks grafted ‘Shatang mandarin’ decreased in different degrees, while the reducing sugar content of the fruits was lower than that of ‘Shatang mandarin’ rootstocks. The reducing sugar content of fruit was significantly increased after grafting with 9 rootstocks such as ‘Wangcangdayezhi trifolicate orange’. In the correlation analysis, there was a significant negative correlation between plant height and SPAD value, indicating that dwarfing rootstocks could effectively improve photosynthesis by increasing the absorption of light energy by leaves, and there was a significant positive correlation between fruits weight per plant and plant height, indicating that the dwarfing caused by rootstocks would affect the fruits weight per plant; Single fruit weight was significantly positively correlated with pulp weight, fruit transverse and longitudinal diameter, and fruit volume, indicating that several indicators in measuring fruit weight and size would interact with each other. The correlation of 22 indicators shows that there are different degrees of correlation between indicators, which shows that there is information overlap between multiple indicators, and the evaluation indicators need to be simplified. In the principal component analysis, 6 principal components were extracted, and the cumulative contribution rate reached 93. 407%, indicating that the 6 principal components could represent most of the information of the 22 indicators. The cumulative contribution rate of the first four principal components reached 80. 258%, and the key factors in the all 6 principal components could be used as the core indicators to evaluate the 10 rootstocks. Finally, Construction of comprehensive evaluation model for selecting superior rootstocks of grafted ‘Shatang mandarin’. According to the comprehensive score, the results showed that ‘Red limonia’ rootstocks had the highest score, followed by ‘Xiangcheng’ rootstocks and ‘Rough lemon’ rootstocks. 【Conclusion】 Through the determination of related indexes of ‘Shatang mandarin’ grafted with ten rootstocks under screen house cultivation, it was found that there were significant differences among plant height, fruits weight per plant and fruit quality, and there were also multiple correlations among the indexes. The joint analysis of these indexes was conducive to understanding the relationship among plant height, yield and fruit quality. The comprehensive evaluation model of rootstocks screening was established based on the 22 related indicators obtained by principal component analysis, and the 6 key factors in all 6 principal components could be used as the core indicators to evaluate the 10 rootstocks, and the comprehensive evaluation scores of the 10 rootstocks were calculated and sorted from high to low. The results indicate that ‘Red limonia’, ‘Xiangcheng’, and ‘Rough lemon’ can be recommended as the three preferred dwarfing rootstocks for ‘Shatang mandarin’ in Guangdong Province.
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