Interactions between cyst nematode (Heterodera glycines) and charcoal rot fungus (Macrophomina phaselolina) in susceptible and resistant soybean cultivars to the nematode

Interactions between the cyst nematode Heterodera glycines and charcoal rot fungus (Macrophomina phaselolina) in susceptible cultivars JK and Williams and Katol as a resistant cultivar were studied in greenhouse conditions. Treatments were evaluated by factorial test with two factors treatment and cultivar, six treatments of inoculation including healthy plants, nematode alone, fungus alone, primary inoculation with fungus and two weeks later with nematode, primary inoculation with nematode and two weeks later with fungus and inoculation with fungus and nematodes simultaneously. Experiments were conducted in three levels of cultivars in Random Complete Block Design with five replications. Twenty eggs and second stage juveniles of nematode and two microliters of spore’s suspension per gram of soils were inoculated at two leaves stage of the seedlings. The inoculated seedlings were kept at 25-27 °C in greenhouse conditions. The growth factors, yields of plant, disease severity and nematode reproduction factor were evaluated after five months. In Katol resistance cultivar, the severity of charcoal rot disease did not show significant difference in treatments and there was no interaction. In JK susceptible cultivar, the severity of disease was the same in the treatments and reproduction occurred in all treatments but was not affected by fungal treatment. In Williams cultivar, inoculation with fungus and then nematode, the disease severity was significantly different from other treatments so that it can be stated that there was interaction between fungus and nematode but nematode reproduction was not affected by fungal treatments.