Selection of excellent rootstocks for Shatang mandarin based on combined analysis of plant height, yield, and quality

Abstract: 【Objective】The study aims to establish a comprehensive evaluation for the selection of superior rootstocks for Shatang mandarin by analyzing the plant height, fruit yield and fruit quality of Shatang mandarin on different rootstocks under netted house cultivation.【Methods】Ten different rootstocks were grafted with Shatang mandarin. The difference significance analysis and correlation analysis were carried out on 22 indexes related to plant height, fruit weight per plant and fruit internal and external quality. Finally, the 22 indexes were subject to principal component analysis to obtain the core indexes for the selection of Shatang mandarin rootstocks, and a comprehensive evaluation for rootstocks was thus constructed.【Results】The results showed that there were significant differences in plant height, fruit weight per plant and fruit internal and external quality of Shatang mandarin among the ten citrus rootstocks. The plant height on Sour pummelo was not significantly different from the self-rooted Shatang mandarin. Plant height on Flying dragon trifoliate orange was significantly reduced (50.79% )that on self- rooted plant, showing dwarfing effect of Flying dragon trifoliate orange rootstocks. In the results of soil and plant analyzer development (SPAD) value, it could be seen that Flying dragon trifoliate orange rootstocks with strongest dwarfing effect had the highest SPAD value, reaching 71.92. Selfrooted on Shatang mandarin had the highest plant height, on the contrary, the SPAD value was the lowest, which was 59.44, and the SPAD values of the other rootstocks were also higher than that of Shatang mandarin, which indicated that there was a certain correlation between plant height and SPAD value. Under the unified production management, yield per plant of Shatang mandarin on Goutou sour orange rootstocks was the highest. Different rootstocks had differential effects on 19 indexes related to fruit quality. The single fruit weight and pulp weight in plants on Xiangcheng and Red limonia were higher than those on the other 8 rootstocks, while the single fruit weight and pulp weight in plants on 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 and Red limonia rootstocks were bigger, and the shape was round or nearly round, while the fruit of Goutou sour orange rootstock was the smallest, and the shape was oval or conical. Different rootstocks had different effects on the pericarp characteristics of Shatang mandarin. For the color of the pericarp, the fruit from plants on rootstocks all showed shiny orange, but the fruit surface color of Xiangcheng rootstock was lighter. Of the 10 rootstocks, Shatang mandarin rootstock had the highest soluble solids content, and Xiangcheng rootstock resulted the lowest soluble solid content. The results showed that the soluble solid in Shatang mandarin grafted on the other 9 rootstocks was lower than that of self-rooted Shatang mandarin. Similarly, the titratable acid content of Shatang mandarin rootstock 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 self- rooted Shatang mandarin, the titratable acid content of the fruit in the other 9 rootstocks decreased in different degrees, while the reducing sugar content of the fruit was lower. The reducing sugar content was significantly increased by the 9 rootstocks. 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 fruit weight per plant and plant height, indicating that the dwarfing effect caused by rootstocks might lead to productivity reduction. Single fruit weight was significantly positively correlated with pulp weight, fruit transverse and longitudinal diameters, and fruit volume. The correlation of 22 indicators shows that there were different degrees of correlation between indicators, which shows that there was 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 for Shatang mandarin. According to the comprehensive score, Red limonia rootstock had the highest score, followed by Xiangcheng and Rough lemon rootstocks.【Conclusion】Through the determination of related indexes of Shatang mandarin grafted on ten rootstocks under netted house cultivation, it was found that there were significant differences among plant height, fruit 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. A comprehensive evaluationmodel of rootstocks was established based on principal component analysis of the 22 related indicators, 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 ranked. The results indicate that Red limonia, Xiangcheng, and Rough lemon can be recommended as preferred dwarfing rootstocks for Shatang mandarin in Guangdong Province.