Interactive Effects of AM Fungi and Fungicide Stress on Tomato Growth and Physiology

Abstract Fungal diseases frequently lower the output of tomatoes (Solanum lycopersicum L.), which makes the use of fungicides necessary. Fungicides are good at controlling infections, but they can also interfere with the growth of arbuscular mycorrhizal fungi (AMF), which improve plant health, nutrient uptake, and stress tolerance. The combined effects of fungicide treatment and AMF inoculation on tomato physiology are evaluated in this study by measuring proline accumulation, total chlorophyll, chlorophyll-a, chlorophyll-b, carotenoid content, and AMF root colonization. Three fungicide doses—recommended (R), half-recommended (R/2), and double-recommended (R×2)—were applied to tomato plants with and without AMF infection. Proline buildup in non-mycorrhizal (-AMF) plants was much higher, according to the results, especially when treated with R×2, which may indicate oxidative stress. AMF-inoculated plants, on the other hand, showed less proline accumulation; R/2 (+AMF) showed the greatest stress alleviation. Chlorophyll and carotenoid levels were likewise greater in plants treated with AMF; fungicide-induced phytotoxicity was indicated by the lowest total chlorophyll content (R×2 (-AMF)) and the greatest (R/2 (+AMF)). The detrimental effects of excessive fungicide use on AMF establishment were demonstrated by the fact that AMF root colonization peaked in R/2 (+AMF) (65%) but decreased with increasing fungicide doses. ANOVA results were not statistically significant (p > 0.05), despite the presence of physiological trends, indicating that longer experimental times could be required to draw firm conclusions. These results demonstrate the protective function of AMF in reducing stress caused by fungicides and emphasize how crucial it is to apply fungicides as efficiently as possible in order to balance disease prevention with the health of soil microbes. AMF can lower chemical inputs and encourage sustainable tomato production when it is incorporated into integrated pest control (IPM) programs.