Induced Variability of Resistance to Root-Knot Nematodes (Meloidogyne incognita) in Soybeans (Glycine max)

The purpose of this study was to determine the variability of resistance to root-knot nematodes (Meloidogyne incognita) in soybeans (Glycine max) induced by seed treatment with ethylmethane sulfonate (EMS).

Two soybean varieties, 'Essex' and 'Forrest,' were chosen as the experimental materials mainly on the basis of their distinct level of resistance; 'Essex' is susceptible and 'Forrest' is resistant. The M₂ and control populations were grown and tested for nematode resistance in the greenhouse. The number of gall developed on the roots was used to indicate the level of resistance.

The frequency distribution of the M₂ population of 'Essex' was found to be significantly different from that of the control (P < 0.01). The variability of resistance was broadened by the EMS treatment. The M₂ population of 'Forrest' showed no significant difference in the frequency distribution as compared with the control (0.50< P < 0.60). The EMS treatment did not significantly alter the variability of resistance.

It is suggested that the probability of altering the variability of resistance to root-knot nematodes through induced mutations is greater in susceptible varieties and in resistant varieties.