To investigate the effect of calcium (Ca) application on post-harvest fruit quality in Nanfeng tangerines, this study sprayed three calcium fertilizers (Calbit, Larry 8 Calcium, and Suspended Calcium) before harvesting. The fruit quality was assessed over a storage period of 0–60 d at a controlled room temperature of 20 ± 5 °C. The evaluation methods included principal component analysis (PCA) and linearly weighted summation. Pre-harvest calcium treatments increased the fruit calcium content and maintained higher firmness and shear. Compared to the control group, fruits treated with Calbit exhibited decreased levels of decay, weight loss, and respiration rates. Additionally, they demonstrated higher values of L*, b*, C*, and H° and lower values of a* and CCI. Moreover, the Larry 8 Calcium and Calbit treatments increased the levels of soluble solids, total soluble sugars, titratable acids, and VC content in the fruit. They accelerated the decomposition of tartaric, oxalic, and citric acids in the pulp, promoting the accumulation of sucrose and glucose. PCA and comprehensive evaluation scores indicated that the comprehensive scores assessing the storage quality of Nanfeng tangerine fruits treated with pre-harvest Larry 8 Calcium and Calbit were higher than those of the control group. The highest composite quality scores for Calbit-treated fruits were observed at 40 and 60 d, and the highest scores for Larry 8 Calcium were recorded at other intervals. These findings suggest that pre-harvest calcium application improved the post-harvest fruit quality of Nanfeng tangerines, with Larry 8 Calcium and Calbit emerging as favorable options.

Dwarfing rootstocks are capable of high-density planting and are therefore urgently needed in the modern citrus cultivation system. However, little is known about the physiological relevance and molecular basis underlying citrus height. This study aimed to comprehensively analyze phytohormone, carbohydrate, and associated transcriptome changes in the stem of two weak growth rootstocks (‘TO’ and ‘FD’) relative to the vigorous ‘CC’ rootstock. The phenotypic observation revealed that the plant height, plant weight, and internode length were reduced in dwarfing rootstocks. Moreover, the contents of indole-3-acetic acid (IAA), trans-zeatin (tZ), and abscisic acid (ABA), were higher in TO and FD rootstocks, whereas the gibberellin 3 (GA3) content was higher in the CC rootstocks. The carbohydrate contents, including sucrose, fructose, glucose, starch, and lignin significantly decreased in both the TO and FD rootstocks. The full-length transcriptome analysis revealed a potential mechanism regulating dwarfing phenotype that was mainly related to the phytohormone signaling transduction, sugar and starch degradation, lignin synthesis, and cellulose and hemicellulose degradation processes. In addition, many transcription factors (TFs), long non-coding RNAs (lncRNAs), and alternative splicing (AS) events were identified, which might act as important contributors to control the stem elongation and development in the weak growth rootstocks. These findings might deepen the understanding of the complex mechanisms of the stem development responsible for citrus dwarfing and provide a series of candidate genes for the application in breeding new rootstocks with intensive dwarfing.