Abstract: In order to study the effects of regulated deficit irrigation (RDI) on the yield and quality of tomato under high temperature and high humidity environment in the Meiyu season, a field experiment was conducted in the solar greenhouse of Nanjing University of Information Technology during the Meiyu season from June to July in 2021. Using adequate irrigation (100% ET₀) as the control (CK), three levels of RDI treatments were set up from flowering to fruiting stage of tomato, which were T1 (90% ET₀), T2 (75% ET₀) and T3 (50% ET₀) respectively. The growth indices, nutritional quality, sensory quality and yield of tomato under different irrigation treatments were measured. The results showed that the plant height, leaf area, dry matter accumulation of root, stem and leaf of tomato increased first and then decreased with the decrease of irrigation amount. The plant height, leaf area, dry matter accumulation of root, stem and leaf of tomato in T1 treatment were the highest, followed by T2 treatment, and which were significantly higher than CK and T3 treatment. The yield of each treatment was T1>T2>CK>T3. The yield of T1 and T2 treatments were 23.21% and 9.33% higher than that of CK respectively, while that of T3 treatment was 19.36% lower than that of CK. The content of soluble protein, soluble solids, soluble sugar, titratable acid, the ratio of sugar to acid and the sensory quality such as color, luster, smell, peel thickness and sweetness all increased first and then decreased with the decrease of irrigation amount. Nutritional quality indicators such as soluble protein content, soluble solids content, soluble sugar content, titratable acid content, sugar-acid ratio, and sensory quality indicators such as fruit color, luster, aroma, pericarp thickness, sweetness also increased first and then decreased with the decrease of irrigation amount. The soluble solid content, soluble sugar content, sugar-acid ratio, fruit color, fruit smell, fruit sweetness and pericarp thickness of T2 treatment were the highest, followed by T1 treatment. The nutritional quality and sensory quality of fruits were evaluated by membership function method, and the results were T2>T1>T3>CK. According to the growth status of tomato plants, the nutritional quality, sensory quality and yield of tomato fruits, T1 treatment could significantly promote the growth of tomato plants, increase fruit yield and improve fruit quality under the environmental conditions of high temperature and high relative humidity in Meiyu season. Therefore, T1 treatment is the recommended irrigation amount for greenhouse tomato from flowering to fruiting stage under the high temperature and high humidity environment in Meiyu season of Nanjing.

Key words: Meiyu season, High temperature and high humidity, Regulated deficit irrigation, Greenhouse tomato, Yield and quality