Figure 1.

Effect of exogenous melatonin pre‐treatment on cotton resistance to Verticillium dahliae.

(a) Disease symptoms of cotton plants pre‐treated with different melatonin concentrations (0, 10, 25, 50, and 100 μm) following inoculation with V. dahliae strain Vd086 at 22 dpi. Bar = 1 cm.

(b) Fungal accumulation in the stems of cotton plants pre‐treated with different concentrations of melatonin at 22 dpi. Bar = 1 cm.

(c) Growth of hyphae recovered from the V. dahliae‐infected cotton. The stem sections were plated on PDA medium, incubated at 25°C, and photographed at 5 days post plating. Bar = 1 cm.

(d) Disease indexes of the melatonin‐pre‐treated cotton were determined from 10 dpi to 32 dpi. The values are the means ± SD; n = 32.

(e) Detection for the relative quantification of fungal biomass. Total DNA from the leaves of melatonin‐pre‐treated cotton plants inoculated with V. dahliae for 22 days was extracted as the template for fungal biomass detection by qPCR. GhUBQ7 was used as the internal control. The values are the means ± SD; n = 3. Statistical analyses were performed using Student's t test. *, P < 0.05; **, P < 0.01.