Water Limitation Causes Early-Stage Metabolic Perturbation in the Interaction of Soybean and Asian Soybean Rust

Soybean is a valuable commodity, and its production has
been menaced
by more frequent drought events and Asian soybean rust, caused by Phakopsora pachyrhizi. This study compared the leaf
metabolic profile of soybean plants exposed or not to controlled water
limitation and then infected with rust at the beginning of fungal
colonization. Disease severity was enhanced in plants grown with water
limitation, which also had contrasting metabolic profiles compared
with those with regular irrigation. Water limitation associated with
disease increased defense-related compounds at both 12 and 24 h after
inoculation. Naringenin and daidzein, among other flavonoids, accumulated
more in inoculated plants, even more so when soybeans were grown in
water limitation. Amino acid concentration was negatively correlated
with water limitation, which could compromise plant immunity and explain
why plants with a stress combination had higher disease severity.
The results help us to understand the complex interaction between
drought and disease severity, a condition found in the tropics.