Comparison of Two Inoculum Preparation Methods for Rotylenchulus reniformis

Abstract

Three greenhouse experiments were conducted to determine whether NaOCl-extracted eggs would provide an acceptable inoculum source for Rotylenchulus reniformis. Two tests (one each on loamy sand and sandy clay) were designed to compare eggs extracted from roots with sodium hypochlorite (NaOCl) with mechanically extracted vermiform males, females, and juveniles from soil as inoculum sources. Infection rates for both inoculum types were low ( 1-3%) on roots of 'Ransom' soybean 14 days (loamy sand soil) or 30 days (sandy clay soil) after inoculation. A larger number of infective females from the mechanically extracted than from NaOCl-extracted inoculum penetrated the roots in the loamy sand; however, in the heavier soil (sandy clay), NaOCl-extracted eggs were the better inoculum source. Significant reproduction occurred on infected plants, regardless of inoculum preparation method or soil type. Extraction of eggs by the NaOCl method is much easier and quicker than mechanical extraction of vermiform nematodes from soil. A third test was conducted to determine the infectivity of R. reniformis from eggs extracted at different NaOC1 concentrations. Five initial inocnlum levels (0, 500, 2,500, 5,000, and 10,000) and four NaOC1 concentrations (0.25, 0.50, 0.75, and 1.0%) were compared on 'Rutgers' tomato harvested on two dates, 17 and 23 days after inoculation. Again, infection rates of roots were low ( =10-3%). By 23 days after inoculation, the largest number of females penetrating the roots were from the highest inoculum level extracted with 0.25% NaOCl. The lowest infection rates in both harvests occurred when inoculum was prepared with 1.0% NaOC1. Key words: Glycine max, inoculum, Lycopersicon esculentum, nematode, reniform nematode, Rotylenchulus reniformis, soybean, tomato.