Effects of alfalfa mosaic disease on photosynthetic performance, growth, and forage quality of Medicago sativa

This study aimed to determine the effect of alfalfa mosaic disease on the photosynthetic performance, growth, and forage quality of alfalfa and to evaluate the losses caused by the disease. In comparison to healthy plants, the chlorophyll content, net photosynthetic rate (P_n), transpiration rate (T_r), and stomatal conductance (G_s) of leaves from infected plants were reduced by 35.16%, 93.3%, 65.4%, and 40%, respectively, whereas intercellular CO₂ concentration (C_i) was increased by 42.52%. Plant biomass, height, leaf width, and leaf length were also reduced by infection (P < 0.01), by 29.50%, 28.74%, 39.84%, 26.27%, respectively, and the correlation coefficients of disease severity with them were –0.85, 0.953, –0.98, –0.87, respectively. Alfalfa mosaic disease also reduced crude protein and crude fat contents (by 42.70% and 70.82%, respectively) and increased acid detergent fiber and neutral detergent fiber contents (by 49.29% and 23.99%, respectively). Growth, forage quality, and photosynthesis indicators exhibited significant or significant correlations with disease severity. Growth, quality indicators exhibited significant or significant correlations with photosynthesis indicators (chlorophyll content, P_n, T_r, C_i). This indicates that alfalfa mosaic disease affects photosynthesis, which in turn affects alfalfa growth and forage quality.