VARIATION AMONG POPULATIONS OF SOYBEAN CYST NEMATODE, HETERODERA GLYCINES, FROM GEOGRAPHICALLY SEPARATED AREAS OF INDIANA

JAMALEDIN FAGHIHI, Purdue University

Abstract

Five populations of soybean cyst nematode (SCN), Heterodera glycines, were maintained in the greenhouse for comparative studies of their morphology and their responses to root zone temperatures and a wide range of soybean differentials. These populations represented two geographically separated areas in the northern third of Indiana (Whit and Benton Counties) and three areas of the southern quarter of the state (Vigo, Posey and Vanderburg Counties). The populations could be divided into 2-5 groups on the basis of selected morphological characters of second stage juveniles. Characters of males, cysts and eggs were less useful for differentiating populations. In comparisons between a northern population (White) and a southern population (Vigo) no development of either population occurred at 10(DEGREES)C and very little reproduction was observed at 32(DEGREES)C. The White County population reproduced better than the Vigo County population at 17(DEGREES) and 20(DEGREES)C. Both populations reproduced best at 24(DEGREES) and 28(DEGREES)C. All five populations reacted similarly on 11 differentials which included four of the original "standard" differentials (proposed by soybean workers in 1970 for identification of SCN races). The populations reacted differently to a second groups of differentials, which included the variety Pickett. Two nematicides (aldicarb and fonofos) were compared in the field in White County, IN. Aldicarb controlled the nematode population early in the season and resulted in much greater soybean yields than those obtained from untreated plots, but the final SCN population in the treated plots was either equal to or higher than that of untreated check plots. In contrast, fonofos gave less control than aldicarb, but the reduction in SCN population persisted throughout the growing season.

Degree

Ph.D.

Subject Area

Entomology

COinS