Effect of the liquid fertilizer containing fulvic acid on metabolism of cembratrien-diols in flue-cured tobacco

Objectives This experiment was conducted to investigate the effect of the new liquid fertilizer containing fulvic acid for tobacco on metabolism of cembratrien-diols in flue-cured tobacco.

Methods Flue-cured tobacco cultivar ‘Yuyan 6’ was used as material. The treatments included conventional practice (FP), ordinary liquid fertilizer for tobacco (DF1) and liquid fertilizer containing fulvic acid for tobacco (DF2), which were all applied with drip irrigation. The morphology and density of glandular hairs were observed, the glandular trichome exudates were measured, the relative expressions of CYC-1, CYP71D16, DXR and DXS were determined using RT-qPCR, and the content of solanone and sensory quality were evaluated.

Results 1) The trichome density in DF2 treatment was higher and the number of long handle trichomes was more than the other two treatments. The content of cembratrien-diols in glandular trichome exudates was in order of DF2 (65.43 μg/cm²) > FP (46.84 μg/cm²) > DF1(39.8 μg/cm²); 2) The relative expression of CYC-1, CYP71D16, DXR and DXS in DF2 treatment were significantly higher than in DF1 treatment, which were 12.45 times, 3.54 times, 3.22 times and 3.44 times than FP treatment and 4.11 times, 5.71 times, 2.44 times and 2.28 times of those in DF1, respectively; 3) The content of solanone in modulated flue-cured tobacco leaves in DF2 treatment was higher than in the other treatments and reached 112.27 µg/g, which is 2.93 times and 1.99 times of that in FP and DF1, respectively. The sensory quality of tobacco in DF2 treatment was better than in the other treatments in 2015 to 2016.

Conclusions The fulvic acid contained in the liquid fertilizer stimulates the expression levels of genes related cembratrien-diols synthesis, meliorated foliar secretion of flue cured tobacco and improved the content of solanone and the sensory quality evaluation.