Figure 10.

Endogenous contents of phytomelatonin, SA, and tJA detected in leaves of some citrus varieties with different degrees of tolerance to Ca. L. asiaticus using targeted GC-MS-SIM. A, D, and G, Representative chromatograms of melatonin (A), SA (D), and tJA (G) from different varieties. RT, Retention time. B, E, and H, Endogenous contents of melatonin (pg g⁻¹ fresh weight; n = 6), SA (ng g⁻¹ fresh weight; n = 6), and tJA (ng g⁻¹ fresh weight; n = 6), respectively, from different varieties. Whiskers indicate the minimum and maximum values of the data, horizontal thick lines show the medians, black dots indicate the raw data, and boxes show the interquartile ranges (25th to 75th percentiles of the data). Different letters indicate statistically significant differences among varieties, while the same letter signifies no significant differences between them using Tukey’s HSD (P < 0.05). C, F, and I, Simple linear regression analysis between the HLB tolerance degree and endogenous content of melatonin (C), SA (F), and tJA (I). Dots represent the raw data. The fitted regression line is presented as a solid line. The 95% confidence intervals for the estimated regression are gray shaded and edged by dotted lines. Regression equations, R², R²_adj, and P value based on the F test (P ≤ 0.05) were also obtained and are presented within the graphs. FW, Fresh weight. Citrus varieties are as follows, from left to right: VS, Valencia sweet orange; DG, Duncan grapefruit (Citrus paradisi); CM, alemow (Citrus macrophylla); ML, Mexican lime (Citrus aurantifolia); CL, Khasi papeda (Citrus latipes); DT, Dancy tangerine (Citrus tangerina).