Soybean seed composition in cultivars differing in resistance to charcoal rot ( Macrophomina phaseolina)

Seed composition in soybean [Glycine max (L) Merr.] has not been well investigated under charcoal rot infestation under irrigated and non-irrigated conditions. The objective of the present experiment was to assess seed composition and nitrogen fixation under these conditions. No significant differences in protein levels in the moderately resistant germplasm line DT97-4290 were observed under these conditions. Under irrigation, protein concentration was significantly (Pf0.05) higher for the susceptible cultivars Egyptian and Pharaoh under non-infested than infested conditions. The opposite response for protein was observed under non-irrigated conditions for Pharaoh. Oleic acid concentration was significantly (Pf0.001) higher in susceptible cultivars under infested conditions. The concentration of linolenic acid in susceptible cultivars was significantly lower under infested conditions. The enrichment of Delta N in susceptible cultivars under infested conditions indicated that nitrogen fixation was substantially inhibited, but soil nitrogen was used for compensating for atmospheric nitrogen inhibition. These results indicate that charcoal rot infection may alter seed composition and nitrogen fixation in soybean. The alteration in seed composition depended on cultivar susceptibility to charcoal rot and irrigation management.