The Effect of Different Nitrogen Forms on Tomato Spotted Wilt Virus Infection in Pepper Plants Grown in Full and Deficient-Water Conditions

Abiotic stress factors have an impact on both plants and their pathogens. Water and nutrient deficiencies are among the major abiotic stress factors in agricultural systems. Viruses are obligate parasite pathogens causing detrimental yield reductions on crop plants worldwide. However, there have been limited studies on the impact of abiotic factors on plant-virus interactions. In this study, the effects of different forms of nitrogen (N) fertilizers on Tomato spotted wilt virus (TSWV) infection in pepper plants grown under two different irrigation regimes [water deficient (30%) and full irrigation] were investigated in a growth room condition. Fertilizer applications consisted of five individual treatments with three replications. The pepper plants were supplied with 12 kg of N/da using different sources of nitrogen [urea (CH4N2O), NH4NO3, Mg(NO3)2 and (NH4)2SO4]. MgSO4 was also added to the experiment for comparison of the effects of Mg2+ and SO42- in the fertilizers. Each treatment consisted of TSWV-inoculated plants, as well as non-inoculated (healthy) and non-fertilized plants as controls. Every plant in all treatments was tested by enzyme-linked immunosorbent assay (ELISA) to confirm virus infection four and eight weeks after mechanical inoculation. The results showed that the virus-inoculated plants treated with urea and NH4NO3 had lower ELISA absorbance values in both deficient and full-irrigated conditions (p<0.01), suggesting greater tolerance to TSWV infection with these fertilizers. Additionally, the plants treated with Mg(NO3)2-containing fertilizer were relatively more affected by the virus under full irrigation than in water-deficient conditions. Conversely, the plants treated with (NH4)2SO4 had high virus content in deficient irrigation conditions. Despite better canopy development in full-irrigated conditions, TSWV symptoms in pepper plants were less prominent in water-deficient conditions than in full irrigation across all nutrient treatments. This study suggests that urea, NH4NO3, and Mg(NO3)2 may provide a positive contribution to plant fitness and virus suppression under water-deficient conditions. It is necessary to conduct further research to determine the impact of different nutrients and water levels on plant-virus interactions in field conditions.