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© 2007 Plant Management Network.
Accepted for publication 18 July 2007. Published 31 October 2007.


Distribution and Damage Caused by Root-Knot Nematodes on Soybean in Southwest Indiana


Greg R. Kruger, Graduate Research Assistant, and Lijuan Xing, Post-Doctoral Research Associate, Department of Botany and Plant Pathology; Judith B. Santini, Research Statistical Analyst, Department of Agronomy; and Andreas Westphal, Assistant Professor, Department of Botany and Plant Pathology, Purdue University, West Lafayette 47907


Corresponding author: Andreas Westphal. westphal@purdue.edu


Kruger, G. R., Xing, L. J., Santini, J. B., and Westphal, A. 2007. Distribution and damage caused by root-knot nematodes on soybean in southwest Indiana. Online. Plant Health Progress doi:10.1094/PHP-2007-1031-01-RS.


Abstract

The distribution of Meloidogyne spp. in southwestern Indiana was determined in a county-wide survey in two counties and at two farm operations with a history of Meloidogyne infestation. Meloidogyne spp. were found within the Eolian sand deposits in southern Knox Co. and in the northern and central parts of Daviess Co. Meloidogyne spp. were found in approximately 80% of production fields on the two farms south-southeast of Vincennes, Knox Co. In addition, a transect study was conducted in a soybean (cv. 93M90) field to quantify suspected damage from Meloidogyne incognita. In this field, areas of varying sizes contained stunted and chlorotic soybean plants typical of nematode damage. In single transects through each of three damaged areas, plant weights, nematode-induced root galling, nematode densities, and soil chemical and physical properties were taken at 1.5-m intervals. Multiple regression analysis was conducted with the plant, nematode, and soil parameters determined for each location. The amount of nematode-induced galling had the greatest contribution (RČ = 0.40, P < 0.01) to reduced plant top biomass in the damaged soybean areas.


Introduction

In the US and Ontario, Canada, over 93,000 metric tons of soybean yield were lost annually between 1999 and 2002 due to Meloidogyne spp. (4), primarily M. incognita, M. hapla, M. arenaria, and M. javanica. Although M. hapla and M. incognita have been reported in the northern US and southern Canada (1,3,4), M. javanica and M. arenaria have not. In the Eolian sand deposits in southwestern Indiana, crop rotations often include watermelon, soybean, and corn, all of which are hosts for M. incognita. In this study, the distribution and damage potential of Meloidogyne spp. on soybean were documented in southwestern Indiana.


Distribution

A survey was conducted in two counties in southwestern Indiana with anecdotal evidence for the presence of Meloidogyne spp. (Fig. 1). Thirty-five samples were collected from Knox Co. (20 random plus 15 in the Eolian sand deposit) and 35 samples from Daviess Co. (21 random plus 14 in the Eolian sand deposit). Pre-selected collection sites (Cropland Data Layer, National Agricultural Statistical Service, USDA, Washington, DC) were tracked with a handheld GPSMAP 76S unit (Garmin Ltd., Olathe, KS) and mapped in ArcView 3.2 (ESRI, Redlands, CA). In addition, a total of 27 fields on two farms (95 and 130 ha) in southern Knox Co. in the Eolian sand deposit were sampled 16 km south-southeast of Vincennes (Fig. 1). At each site, 20 soil cores were taken 0 to 30-cm deep from arbitrary locations within the first 150 m adjacent to the GPS point or in a whole field sampling pattern. Soils were sieved and placed in 950-ml polyethylene pots. To increase the probability of detecting low population densities of Meloidogyne spp., one tomato seedling (cv. Rutgers) per pot was grown in a greenhouse at 23 ± 2°C for three to four months and then examined for nematode-induced root galling.


 

Fig. 1. Map of Knox and Daviess Co. where soil samples were collected for a county-wide survey with emphasis on the Eolian sand deposits and on two farms in Knox Co. 16 km south-southeast of Vincennes. Light blue areas represent Eolian sand deposits, dots represent sample locations: no root-knot nematodes (blue dots) and root-knot nematode present (red dots). The triangle indicates the location of Vincennes, IN.

 

Meloidogyne spp. were detected on the tomato bioassay tools primarily in the Eolian sand deposits of Knox and Daviess counties, with infestations in two of 15 fields in Knox Co. and six of 14 fields in Daviess Co. (Fig. 1). At the farms, Meloidogyne spp. were detected in 13 of 18 production fields on one farm and all of the nine fields on the other farm (Fig. 1). Fields infested with Meloidogyne had a sand content of at least 78%, consistent with findings of previous surveys in other states (1).


Damage

A soybean field located in the Eolian sand deposits in Daviess Co., IN (Fig. 2), was analyzed for root-knot nematode damage by a transect-sampling method (2). The field had been under a corn-soybean rotation and was currently planted to the soybean cultivar Pioneer 93M90, which is resistant to Heterodera glycines and susceptible to M. incognita. On 11 August 2004, one transect line was placed through each of three areas from healthy-looking soybean into an area with stunted plants and then back to vigorously growing soybean. At 1.5-m intervals along the 30-m transect, the plants in 60 cm of row were counted, tops were harvested and weighed, and roots were rated for severity of nematode-induced galling on a scale of 0 to 10. Soil from each sample location was analyzed for soil chemical and physical properties (macro- and micronutrients, pH, and soil texture) and nematode population densities. Standard nematode extraction procedures were used to determine population densities of mobile life stages of nematodes (H. glycines, Meloidogyne spp., Xiphinema spp.), and cyst and egg population densities of H. glycines. The identity of Meloidogyne incognita in this field was confirmed by morphological examination of females and males (J. D. Eisenback, Virginia Tech, Blacksburg, VA).


 

Fig. 2. Stunted and chlorotic soybean plants in a field infested with Meloidogyne incognita.

 

Soybean top weights were higher at the ends of the transects and decreased near the center, whereas root galling was lower at the ends of the transects and higher in the center (Fig. 3). Pearson’s correlation coefficients of 29 of the 37 variables against plant top weight were significant in at least one transect. In the stepwise regression analysis, which included the effects of nutrients, H. glycines, Meloidogyne spp., and the other factors, the arcsine-transformed gall rating had the greatest impact on soybean top weight (RČ = 0.40, P < 0.01). Plant top biomass was inversely related to gall rating (Fig. 4). Several soil nutrients had much weaker effects on top weight (Zn, RČ = 0.15 and P < 0.01; K, RČ = 0.05 and P < 0.01; S, RČ = 0.05 and P < 0.01) than the gall ratings. In all three transects, the soil texture was sand, sandy loam, or loamy sand. Population densities of H. glycines and Xiphinema spp. were low and not associated with soybean growth.


 

Fig. 3. Average soybean plant top biomass and average nematode gall rating on a scale 0 to 10 with standard error for 21 sample locations across three transects in a Meloidogyne incognita-infested field.

 

 

Fig. 4. Relationship between soybean top fresh weight and the transformed [arcsine ( √ (gall rating/10) ] nematode-induced gall rating (scale 0 to 10) in a Meloidogyne incognita-infested field in Daviess Co., IN.

 

In Indiana, H. glycines has been the focus of nematode management in soybean, but the results from this study show that producers in the southwest portion of the state should be aware of the potential for M. incognita damage and the need to manage this nematode.


Literature Cited

1. Allen, J. B., Bond, J. P., and Schmidt, M. E. 2005. Incidence of Meloidogyne incognita and development of resistant soybean germplasm in Illinois. Plant Health Progress doi:10.1094/PHP-2005-0606-01-RS.

2. Scherm, H., Yang, X. B., and Lundeen, P. 1998. Soil variables associated with sudden death syndrome in soybean fields in Iowa. Plant Dis. 82:1152-1157.

3. Walters, S. A., and Barker, K. R. 1994. Current distribution of five major Meloidogyne species in the United States. Plant Dis. 78:772-774.

4. Wrather, J. A., Koenning, S. R., and Anderson, T. R. 2003. Effects of diseases on soybean yield in the United States and Ontario (1999 to 2002). Plant Health Progress doi:10.1094/PHP-2003-0325-01-RV.