Biochemical evaluation of the reaction of Soybean cultivars to Macrophomina phaseolin, causal of charcoal rot

Reaction to the fungal infection is different in various crops. Biochemical Their complex reactions are of the most important defensive mechanisms of the host plants against pathogens. Macrophomina phaseolina is the causal agent of charcoal rot in soybean with high economical damage of plant. In this research, the resistance reaction of five soybean cultivars (Sari, Sahar, Katol, Gorgan3 and Williams) against Macrophomina phaseolina was studied. Additionally, understanding the changes of total phenol and total protein of three cultivars Sari, Gorgan3 and Williams were measured. The measurements were done in 3 different times before, and 48 and 96 hours after inoculation. The experiment was conducted as factorial based on the completely randomized design with four replication in a greenhouse conditions. Results showed a significant difference (P≤0.05) in reactions of cultivars to studied fungus. Based on the Mean value comparison of data, Cultivars were divided into three different groups of susceptibility: Williams's cultivar with %74/99 infections as very susceptible, Sari and Katool with %20/82 and %24/99 of infections, respectively, as moderate resistant group, finally Sahar and Gorgan3 with 41/66 and%45/83 infections, respectively, were grouped as less susceptible. In addition, a significant difference (P≤0.01) was found between total protein and total phenol content of the three varieties in the 48 hours after inoculation. No significant difference was observed in total phenol and total protein of experimental cultivars in different inoculation times. As no significant differences were observed in total phenolic contents (as indicator in plant stress), the moderate resistance reaction especially in Sari cultivar, could be explained due to presence of phytoallexins as important compounds to prevent pathogen damages in host plants.