Effect Of Crop Rotations On Population Of Heterodera Avenae

Heterodera avenae is a serious threat on wheat production. It’s causing a serious field loss and widely distributes around the world. Some trials were conducted in 2011 and 2012 to determine the impact of four different crops include wheat, oilseed rape, broad bean and pea on population of cysts and eggs under field. Hatching of cysts, life and chemotaxis of juveniles, and fungi in cysts were also been researched under different crops. Two biocontrol fungi were selected for further study. The results were as follow:The population of cysts was reduced at a ratio of 45% in crop rotation field of broad bean, and 42% of oilseed rape,37% of pea. But the reduction ratio of population of cysts in the field of wheat was only 2%. The reduction ratio of eggs in field of pea was greater than in field of oilseed rape, broad bean and wheat. The pots test result shows that broad bean has the greatest reduction ratio of cysts than other crops while it’s reduction ratio less than in field. Reductions ratio of eggs in pots test of all crops were about 90%.The root exudate of pea promoted the hatching of cysts at a temperature of 15℃ (19.3) while the root exudate of broad bean inhibited the hatching (2). Wheat and oilseed rape root exudate had the same impact compared with water on hatching (about 9). The root exudate of broad bean impacted the activity of juveniles. It killed the juveniles at some extent. But the other crops had not any impact on hatching. Wheat root attracted juveniles, however other crops had no impact on chemotaxis of nematodes.Fungi that been isolated from cysts showed that there are more fungi in cysts from wheat than other crops. Isolate rate of fungi in cysts was 53% from wheat while the isolate rates from other crops were about 30%. Infection test of 40 isolates showed that fungi from wheat have a higher infection rate than others. Eight fungi were selected for eggs parasitic ability test. The results showed that two fungi (A31 and A13) have parasitism to eggs. The parasitic rate after 16 days of A31 was 90%, and A13 was 16%. A31 could inhibit the hatching of eggs at a rate of 19%. A13 had not any impact on hatching of eggs. Identifications of these two fungi through morphology and molecule showed that A31 is Pochonia chlamydosporia. This fungus grows slowly with a milky white colony and villiform mycelium. Chlamydospores of A31 can be seen under microscope. A13 is Microdochium bolleyi. The colony which is black grows fast and has oval or crescent-shaped conidia which born in extreme short conidiophore.