THE EFFECT OF WATER STRESS ON THE SURVIVAL OF COMMON CEREAL ROOT-LESION NEMATODES (Pratylenchus neglectus AND P. thornei), UNDER LABORATORY, GREENHOUSE, MICROPLATS AND FIELD CONDITIONS

Pratylenchus neglectus and P. thornei are the common root-lesion nematodes in irrigated wheat and corn fields in Marvdasht region, Iran. Quiescence of these nematodes in response to water stress (anhydrobiosis) and their return to active stage in wet condition is their important strategy to survive in dried soil. Anhydrobiotic states and infectivity of these two root lesion-nematodes were studied under laboratory, greenhouse, microplats and field conditions. The laboratory results indicated that the highest percentage of quiescent P. thornei became active after the infested dried soil was wetted and kept at 25 °C for 72 hrs. In the greenhouse, 86.3% of P. neglectus were alive in 4 cm air-dried soil layer after 4 months. In microplats, without rainfall the populations of two species remained constant for eight months; however, in plots that received natural rainfalls, the populations of both species were dramatically decreased. Under field conditions, all stages of nematodes survived in anhydrobiotic state. In general, anhydrobiosis is important in relation to population maintenance and survival of root lesion nematodes during winter and summer in Marvdasht region.