Effect of Shading Intensity on Growth and Leaf Quality of Hainan Cigar Tobacco

In order to explore the optimal light transmittance of cigar wrapper shading cultivation in the Hainan area, 80% (H2), 65% (H3), 50% (H4) and 35% (H5) light transmittance treatments were set to investigate the effects of shading intensity on agronomic traits, tissue structure, physiological indexes, physicochemical properties, appearance quality, sensory quality and wrapper yield of cigar tobacco leaves after the fermentation. The results showed that the stem circumference and dry and fresh weight of each part of cigar tobacco plants gradually decreased as the decreased light transmittance, and the plant height and leaf area showed a trend of first increasing and then decreasing, and the plant height and leaf area of H3 treatment were significantly higher than those in the other treatments (p≤0.05). With the decrease of light transmittance, the thickness of leaf and fence tissue decreased significantly, the thickness of sponge tissue decreased first and then increased, and the tissue structure compactness and grid-to-sea ratio of H3 treatment were the highest. The tensile strength of H3 treatment was 1.83N, which was significantly higher than that in the other treatments. The light transmittance had no significant effect on the total nitrogen content, and the contents of potassium, total sugar, and reducing sugar were H1>H2>H3>H4>H5. The highest nicotine content in H3 treatment was 5.50%. With the decrease of light transmittance, the scores of maturity, oil and gloss of tobacco leaves decreased, and the scores of identity, pulse phase and integrity increased, and the total score of H3 treatment was the highest. With the decrease of light transmittance, aroma quality, aroma volume, miscellaneous gas, aftertaste, sweetness, flammability and gray score all decreased gradually, and the irritation score increased. The aroma, miscellaneous gas, irritation and aftertaste of H2 and H3 treatment were well evaluated. The total yield of cigar leaves in the H4 and H5 treatments was significantly reduced, but there was no significant difference was found between H2/H3 treatments and the control treatment. The yield of wrapper increased at first and then decreased as the decreased light transmittance, and the 65% light transmittance was the highest, and the yield of wrapper were 401.4 kg/hm² and 19.47%, respectively. In summary, this study concluded that in the production of cigar wrapper tobacco leaves in the Hainan producing area, the use of 65% light transmission treatment is conducive to coordinating the growth and development between leaves and other organs and leaf tissues, so that tobacco leaves showed the relatively better physical properties and chemical composition coordination, and achieved the highest wrapper biomass and yield.