Nitrate Reductase Drives Nutrition Control and Disease Resistance in Tomato (Solanum lycopersicum L.) Cultivars

Abstract

Abstract Purpose Nitrogen plays an important role in plant nutrition. Nitrate reductase can increase the activity can rapidly reduce the accumulation of nitrate in plant tissues and indirectly prevent the occurrence of diseases and insect pests. However, the excess of soluble nitrogen compounds in plants will induce plant diseases and insect pests. Methods In this study, the disease-resistant tomato cultivar 'Myko' and its parents were compared with the disease-susceptible tomato cultivar 'Momotaro', and the positive correlation was confirmed between the disease resistance and the enhanced nitrate reductase activity and the up-regulated NR1 (the gene of nitrate reductase). Results The expression level of the NR1 gene and the daily average yield of tomato fruit during the growth period were simulated by the modified Gaussian curve equation (y = YMe−α(x−τ)^2+YB (1 + βt)). Compared with Momotaro, Myoko F1 was less prone to disease and maintained relatively high photosynthetic capacity and fruit producing potential in the later stages, which showed that the above-average daily fruit yield and NR1 gene expression shifted rightward in the Gaussian curve. The high activity of nitrate reductase, and concentration as well as amino acids in Myoko F1 is much lower as compared to Momotaro. Conclusions In summary, the analysis of nitrate reductase genes and the mathematical models adopted indicate that the increase in nitrate reductase activity can promote nitrogen metabolism, reduce the accumulation of nitrate and amino acids in tomato leaves and fruits, and thus reduce the occurrence of tomato early leaf blight.