Resistance to toxin-mediated fungal infection: Role of lignins, isoflavones, other seed phenolics, sugars, and boron in the mechanism of resistance to charcoal rot disease in soybean

Charcoal rot disease in soybean is caused by the fungus Macrophomina phaseolina, which is believed to infect plants from soil through the roots by a toxin-mediated mechanism. Soybean genotypes exist which are susceptible (S) or moderately resistant (MR) to charcoal rot, but the mechanism of resistance is not known. Significantly (p ≤ 0.05) higher levels of phenolics, seed coat lignin, isoflavones, sugars, and total boron were observed in MR genotype than in S genotype seeds under irrigated and nonirrigated and under experimental M. phaseolina infested and noninfested conditions, indicating a possible association of these substances with resistance to toxin-mediated infection.