Effect of Crop Rotations on Rotylenchulus reniformis Population Structure.

Rotylenchulus reniformis is a highly variable nematode species and an economically important pest in many cotton fields across the south-eastern United States. Rotation with resistant or poor host crops is a method for management of reniform nematode. We studied the effect of six planting schemes covering four 120-day planting cycles on the predominant genotype of R. reniformis. Rotations used were: (i) cotton to corn; (ii) susceptible soybean to corn; (iii) resistant soybean to cotton; (iv) corn to cotton; (v) continuous susceptible soybean; (vi) continuous cotton. After each 120-day cycle, amplified fragment length polymorphisms (AFLPs) produced from four primer pairs were used to determine the effect of crop rotation on the predominant genotype of reniform nematode. A total of 279 polymorphic bands were scored using four primer combinations. Distinct changes in genotype composition were observed following rotations with resistant soybean or corn. Rotations involving soybean (susceptible and resistant) had the greatest effect on population structure. The characterization of field population variability of reniform nematode and of population responses to host plants used in rotations can help extend the durability of resistant varieties and can help identify effective rotation schemes.