In the study of the biological control of plant-parasitic nematodes, knowledge of the saprophytic ability of a nematophagous fungus is necessary to understand its establishment and survival in the soil. The objectives of this study were (i) to determine if the nematophagous fungus ARF (Arkansas Fungus) shows differential use of plant residues; and (ii) to determine if ARF still existed in the soil of a field in which ARF was found originally and in which the population level of Heterodera glycines had remained very low, despite 15 years of continuous, susceptible soybean. Laboratory studies of the decomposition of wheat straw or soybean root by ARF were conducted in two separate experiments, using a CO₂ collection apparatus, where CO₂-free air was passed through sterilized cotton to remove the microorganisms in the air and then was passed over the samples, and evolved CO₂ was trapped by KOH. Milligrams of C as CO₂ was used to calculate the percentage decomposition of the plant debris by ARF. Data indicated ARF decomposed 11.7% of total organic carbon of the wheat straw and 20.1% of the soybean roots in 6 weeks. In the field soil study, 21 soil samples were taken randomly from the field. Only 3 months after the infestation of the soil with H. glycines, the percentage of parasitized eggs of H. glycines reached 64 ± 19%, and ARF was isolated from most parasitized eggs of H. glycines. Research results indicated ARF could use plant residues to survive.
ARF; decompose; Heterodera glycines; nematophagous fungus; plant debris; soybean cyst nematode
The reniform nematode, Rotylenchulus reniformis Linford &Oliveira, has become a serious threat to cotton (Gossypium hirsutum L.) production in the United States during the past decade. The objective of this study is to isolate fungi from eggs of R. reniformis and select potential biological control agents for R. reniformis on cotton. Soil samples were collected from cotton fields located in Jefferson County, Arkansas. Eight genera of fungi were included in the 128 fungal isolates obtained, and among them were five strains of the nematophagous fungus ARF. The mtDNA RFLP pattern, colony growth characteristics, and pathogenicity indicate the five ARF isolates represent one described strain and one new strain. Light and electron microscopic observations suggest ARF is an active parasite of R. reniformis, with parasitism ranging from 48% to 79% in in vitro tests. Three greenhouse experiments demonstrated ARF successfully suppressed the number of reniform nematodes during the first and second generation of the nematode. Reductions in numbers of R. reniformis on the roots for the seven application rates of 0.01%, 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, and 0.5% ARF were 87%, 92%, 94%, 96%, 97%, 98%, and and 98%, respectively.
ARF; biological control; cotton; Gossypium hirsutum; reniform nematode; Rotylenchulus reniformis
The purpose of this research was to compare the overwinter survival of populations of Heterodera glycines at different latitudes in the United States and the effect of changing latitudes before and after the initiation of dormancy. Soil samples infested with H. glycines were collected in August or October in 1992 to 1994 from soybean fields in two to four states (combinations of Arkansas, Florida, Minnesota, Missouri, and Wisconsin). The samples were mixed thoroughly, divided into subsamples, shipped to an overwinter location, and buried until time for processing. To determine survival, cysts, eggs, and second-stage juveniles were extracted from replicated subsamples and counted each month from December to May. Survival generally was between 50% and 100%, and often was best in the state of origin. In Florida, survival was at the 50 to 100% level in soil from most locations, and in Wisconsin was near 100%. Survival of H. glycines in Arkansas and Missouri varied more than at the other locations. In a separate test, survival in microplots in Arkansas, in a more natural environment than that of buried samples, was 70 to 94% for field isolates from Arkansas, Minnesota, and Missouri and 100% for isolates of races 1, 3, and 14 that had been maintained in a greenhouse for several years. Survival appears to be better than previous tests had indicated. High survival rates require cultivars with high levels of resistance and long-term rotations for management.
Heterodera glycines; nematode; overwintering; soybean cyst nematode; survival
Five soybean cultivars, one each from Maturity Groups (MG) III, IV, V, VI, and VII, all susceptible to Heterodera glycines, were planted in H. glycines-infested soil in April, May, June, and July at multiple locations in Arkansas and Missouri. The purpose of the study was to determine whether planting early reduces yield losses due to H. glycines. The population levels of cysts, eggs, and secondstage juveniles of H. glycines were determined from soil samples collected at planting and harvest. Yields were measured from the two middle rows of 4.9 or 6.1-m four-row plots. The population dynamics of the nematode varied with planting date, cultivar, MG, and initial nematode population. Generally, the lowest reproductive factor (Rf = final population/initial population) for any year was on the MG III cultivar, regardless of planting date or field location. Also, the Rf was generally lower on each cultivar planted in April than in June or July. The highest Rf values were on cultivars in MG VI or VII planted in June or July. Yields were not consistently correlated with initial nematode population level. Early planting of late-maturing soybean cultivars may be profitable, but early planting of MG III cultivars, though supporting little if any increase in nematode numbers, did not result in high yields.
Glycine max; Heterodera glycines; planting dates; population dynamics; soybean; soybean cyst nematode; soybean maturity groups
Eight wild perennial Glycine species (G. argyrea, G. canescens, G. curvata, G. cyrtoloba, G. latifolia, G. microphylla, G. tabacina, and G. tomentella) were evaluated for resistance to isolates of races 1, 3, and 14 of Heterodera glycines. In a second experiment, reproduction of isolates of races 3, 5, and 14 of H. glycines on five of the wild perennial species was determined. Seventy-one derived fertile lines (2n = 40) that were hybrids between G. max cv Clark 63 and G. tomentella also were evaluated for resistance to isolates of races 3, 5, and 14. All of the wild perennial Glycine species were resistant (Female Indices [FI] less than 10) to all of the isolates that were tested on them. In most cases no females matured. The soybean cvs. Clark 63 and Altona, which were tested at the same time as the hybrids, were susceptible to all isolates of H. glycines tested. When the tests were combined and a single FI calculated with the average number of females on Lee 74, one derived fertile line was resistant to race 3, three derived fertile lines were resistant to race 5, and five derived fertile lines were resistant to race 14. Thus, transfer of resistance to H. glycines from G. tomentella to G. max apparently occurred.
Glycine species; Heterodera glycines; interspecific hybrids; nematode; resistance; soybean; soybean cyst nematode
An unnamed fungus, designated ARF, that parasitizes eggs and sedentary stages of cyst nematodes is a potential biological control agent of Heterodera glycines. The objectives of this study were to determine whether ARF isolates differ in their ability to suppress nematode numbers in soil and to compare the efficacy of ARF in heat-treated and native soil. The effectiveness of 11 ARF isolates was compared by introducing homogenized mycelium into heat-treated soil. Soybean seedlings were transplanted into pots containing fungus-infested soil and inoculated with H. glycines. After 30 or 60 days, the number of nematodes and the percentage of parasitized eggs were determined. Three isolates (907, 908, and TN14), which were previously reported to be weak egg parasites in vitro, consistently suppressed nematode numbers by 50% to 100%. Of the isolates previously reported to be aggressive egg parasites, four (903, BG2, MS3, and TN12) reduced nematode numbers by 56% to 69% in at least one experimental trial, but the other four had no effect on nematode numbers. When the efficacy of isolate TN14 was tested in heat-treated and native soil, nematode suppression was greater in the heat-treated soil in only one of two trials. In both soil treatments, nematode numbers were reduced by more than 60%. We conclude that virulence toward nematode eggs in vitro is a poor indicator of effectiveness of an ARF isolate in soil, and that the presence of soil microbes may reduce, but does not completely inhibit, activity of isolate TN14.
ARF; Arkansas Fungus 18; biological control; efficacy; Heterodera glycines; nematode; nematophagous fungus; soybean; soybean cyst nematode; suppression
The objective of this study was to determine the interrelationships of Heterodera glycines races based on their resistance to soybean (Glycine max) cultivars and lines against which they were tested. Greenhouse tests determined the numbers of females of each of eight races of H. glycines that developed on 277 to 522 soybean cultivars and lines. A Female Index (number of females on a test cultivar as a percentage of the number on 'Lee 74') was calculated and used in frequency distributions, correlations, and duster analyses of the resistance reactions to the different races in an attempt to determine relationships among cultivars. Frequency distribution patterns of all cultivars and lines tested against each race were skewed in favor of resistance, and in some cases bimodality was observed. The majority of correlations between pairs of races were highly significant. Cluster analyses based on the correlations divided eight races into four clusters that explained 73% of the variation in resistance. Cluster 1 was comprised of races 2, 4, and 14; Cluster 2 was comprised of races 6 and 9; Cluster 3 was comprised of races 1 and 3; and Cluster 4 was comprised of race 5. The information obtained in this study could increase the efficiency of testing resistant soybean breeding lines for resistance to H. glycines.
Cluster analysis; Glycine max; Heterodera glycines; nematode; resistance; soybean; soybean cyst nematode; virulence group
The effects of 22 pesticides on the mycelial growth and pathogenicity of the biocontrol fungus ARFI8 to Heterodera glycines were tested in vitro. The chemicals were added to agar at 10, 100, and 1,000 ppm a.i.; a block of agar containing the fungus was added to each test concentration; and fungal growth was measured. Subsequently, a block of the fungus on the pesticide-containing agar was used to determine the ability of the fungus to parasitize eggs of H. glycines. Aldicarb, bentazone, and chlorothalonil had little or no effect on fungal growth, whereas benomyl and thiophanate methyl completely inhibited growth of the fungus at 10 ppm. The relative insensitivity of ARF18 to certain pesticides would permit selected use of those pesticides with ARF18 in an integrated control program if the effects on the fungus in the field are similar to results from petri dish studies.
aldicarb; ARF18; benomyl; bentazone; biocontrol fungus; biological control; chemical pesticides; chlorothalonil; Heterodera glycines; nematophagous fungus; pesticide; soybean cyst nematode; thiophanate methyl
A total of 62 populations of Heterodera glycines were collected in 10 states along the Mississippi and Missouri rivers, and 206 populations were collected in Arkansas. Among the 62 populations, races 2, 3, 4, 5, 6, 9, and 14 were found south of 37°N latitude, and races 1 and 3 were found north of 37°N latitude. In Arkansas samples, races 2, 4, 5, 6, 9, and 14 comprised 87% of the populations. In both groups of samples, H. glycines populations with genes that enabled the population to parasitize cv. Pickett occurred the most frequently, followed by those with genes for parasitism of cv. Peking, then PI88.788, and the fewest with genes for parasitism of PI90.763. The diversity of races in this study raises questions about the effectiveness of race-specific cultivars for the management of soybean cyst nematodes. The greater diversity of races of H. glycines in the southern United States may be because of a longer history of planting resistant cultivars.
breeding; geographic distribution; Glycine max; Heterodera glycines; race; resistance; soybean; soybean cyst nematode
Experiments to determine the effects of extraction techniques and the influence of shipping on extraction of Heterodera glycines life stages gave variable results. Shipping did not significantly affect numbers of nematodes extracted. More second-stage juveniles (J2) were extracted with Baermann funnels than with an elutriator, probably because incubation of encysted eggs on the Baermann funnel for 1 week allowed hatching to occur. Sieving was more efficient than elutriation for extracting cysts. Adding air agitation to the water pressure during elutriation increased extraction efficiency of cysts but not J2. Sample sizes of 250 cm³ and 500 cm³ did not influence extraction efficiency of cysts; however, sample size did influence extraction of J2.
Baennann funnel; centrifugal flotation; cyst; egg; elutriation; extraction; Heterodera glycines; methods; nematode; second-stage juvenile; shipping; soybean cyst nematode
Dry alginate-clay pellets containing mycelium of ARF18 were added to sandy soil in greenhouse tests to determine the formulation's efficacy in the suppression of Heterodera glycines. Pellet formulation variables included quantity of mycelium per pellet (0.0-3.9%), pellet size (2.3 or 8.3 mg), pellet application rate per unit soil (0.4 or 1.0% based on dry soil weight), and pellet storage (0 or 90 days). All of these variables affected efficacy. Nematode suppression was greatest (95%) with 8.3 mg pellets containing 3.9% mycelium that were not stored and applied at the rate of 1.0% of dry soil weight. Storage for 90 days reduced the efficacy of the pellets. The soybean cultivars tested were not equally good hosts of H. glycines, but reproduction of the nematode was reduced equally on all. The average suppression was 96% (range 86-99%). Similar suppression of reproduction occurred in tests with six races of H. glycines. ARF18 appeared to be nonspecific with regard to soybean cultivar and H. glycines race.
biological control; carriers; egg parasite; formulation; fungus; Glycine max; Heterodera glycines; kaolin; nematode; nematophagus; race; soybean cyst nematode
Many new cultivars of soybean (Glycine max) are released each year. Knowledge of their relative susceptibility to soybean cyst nematode (Heterodera glycines) is of interest to soybean breeders and those making nematode management recommendations. Two-hundred-eighty-one cultivars and breeding lines of soybean were screened for resistance to isolates of H. glycines races 1, 2, 3, 4, 5, 6, 9, and 14. No cultivar or line (except possibly PI 437654 or cultivars developed from this PI line) had resistance to all of the races tested. Twenty-one cultivars and lines were resistant to race 1, 5 to race 2, 146 to race 3, 2 to race 4, 4 to race 5, 24 to race 6, and 24 to race 14; some had resistance to more than one race. In addition, several cultivars and lines had moderate resistance to each of the race isolates tested.
breeding; cultivar; Glycine max; Heterodera glycines; soybean; soybean cyst nematode; race; resistance
For on-site detection of cysts, a portable cyst extraction kit was constructed from nine readily available items. The portable cyst extractor detected cysts in a range of 1-117 cysts/100 g soil from 42 fields. Samples processed by this kit in fields were clean and easy to examine, possibly because the kit is a compact version of the standard wet-sieving technique used in the laboratory. The portable cyst extractor has several advantages over traditional survey methods: i) diagnosis of cyst infestations in the field accurately and rapidly most of the year and ii) reduction in the labor of samplings and transportation of soil samples.
apparatus; diagnosis; Heterodera; soybean cyst nematode technique
A facultative fungal parasite, Arkansas Fungus 18 (ARF18), was isolated from at least 10 different sources of Heterodera glycines in different areas in the United States. Techniques used for isolation and in vitro evaluation of fungal parasites of H. glycines were described. Successful isolation of probable egg parasites depends on isolation from individual eggs. Selective isolation and a simple, yet definitive, screening system can increase the possibility of identifying effective biocontrol agents.
ARF18; biocontrol; egg parasite; Heterodera glycines; isolation; soybean cyst nematode; nematode suppressive soil; technique
Large pot (2 years) and field experiments (1 year) were conducted to determine the response of susceptible soybean Glycine max (L.) Merr. cultivars (Essex and Hutcheson) grown in soybean-cyst-nematode (SCN), Heterodera glycines-infested soils at three soil water regimes. The soil water regimes were irrigation whenever soil water potential ([psi]s) 0.30-m deep was i) -30 kPa (I-30) or ii) - 50 kPa (I-50), and iii) no irrigation. Cyst nematode levels in the pot experiment were either 0 or 20,000 second-stage juveniles (J2) per pot. The field experiment was conducted on soil naturally infested with a population of 145 to 475 cysts L⁻¹ of soil. All growth parameters studied were drastically affected in the presence of SCN under nonirrigated conditions for the large pot tests; however, SCN did not influence growth parameters in the field experiment. Seed yield was lowest in the no irrigation treatment when all treatments were compared in both the pot and field experiments. The infested no irrigation treatment in the pot experiment had the lowest yield among soil water treatments.
Glycine max; Heterodera glycines; nematode; soil water regime; soybean; soybean cyst nematode
Locations of syncytia induced by the soybean cyst nematode (SCN), Heterodera glycines race 3, were compared in roots of 'Essex', a susceptible soybean (Glycine max (L.) Merr.) cultivar, at three soil water regimes. The plants were grown in wet (-5 to -20 kPa), moderately wet (-30 to -50 kPa), and moderately dry (-60 to -80kPa) autoclaved Captina silt loam soil (Typic Fragiudult). In the moderately dry soil, syncytia were found only in the stele, but in moderately wet and wet soils, syncytia occurred primarily in the cortex and occasionally in the stele. The location of syncytia in the cortical tissue of roots growing in wet and moderately wet soils may account for the tolerance of susceptible soybean cultivars grown under well-irrigated conditions where there is less interference with water transport through roots. Cell-wall perforations and dense cytoplasm were characteristic of syncytial cells observed in root tissues of all treatments.
Glycine max; Heterodera glycines; histology; nematode; soil water; soybean; soybean cyst nematode; syncytia
Thirteen soybean plant introduction (PI) lines, selected for their apparent susceptibility to Heterodera glycines, were compared with cultivar Lee 74 as hosts of H. glycines races 1, 2, 3, and 4. Race 3 produced the highest average number of females of the four races. Compared to Lee 74, more (P = 0.05) females of H. glycines race 1 were extracted from eI 274420, PI 274423, and PI 317333; PI 86457 had more females of H. glycines race 2; and PI 86443, PI 86457, PI 261467, PI 274420, PI 274421, and PI 274423 had more females of H. glycines race 3. Similar numbers of females of H. glycines race 4 developed on all of the soybean lines and Lee 74. PI 274421, PI 274420, or PI 196159 could provide a more or equally susceptible host for H. glycines races 1, 2, 3, and 4 than Lee 74. One of these three lines could be substituted for Lee as the standard susceptible cultivar in the race determination test.
Glycine max; Heterodera glycines; nematode; race; soybean; soybean cyst nematode; susceptibility
Additional tests of 178 cultivars and lines of soybean against soybean cyst nematode are reported. Cultivars are available with some level of resistance to races 1, 2, 3, 4, 5, 6, 9, and 14, but in some cases the resistance level is moderate. No cultivar or line (except possibly PI 437654) has resistance to all of the races tested. Thirteen cultivars and lines, however, were resistant or moderately resistant to race 1, 14 to race 2, 87 to race 3, 2 to race 4, 3 to race 5, 42 to race 6, 18 to race 9, and 36 to race 14. Some have resistance to more than one race.
Glycine max; Heterodera glycines; nematode; resistance; soybean; soybean cyst nematode
A filamentous, nonsporulating fungus, designated Arkansas Fungus 18 (ARF18), was isolated from 9 of 95 populations of Heterodera glycines, the soybean cyst nematode, in Arkansas. In petri dishes, ARF18 parasitized 89% of H. glycines eggs in cysts. The fungus also infected eggs of Meloidogyne incognita and eggs in cysts of Cactodera betulae, H. graminophila, H. lespedezae, H. leuceilyma, H. schachtii, and H. trifolii. In pot tests, reproduction of SCN was 70% less in untreated field soil that was naturally infested by ARF18 than in autoclaved field soil. Although ARF18 grew well at 25 C on cornmeal agar over a wide pH range, it did not sporulate on 28 media and thus could not be identified to genus or species.
Arkansas Fungus 18; biological control; distribution; fungus; Heterodera glycines; host range; hyphomycete; Meloidogyne incognita; soybean cyst nematode; temperature
Effects of pot size, length of seedling radicle at the time of inoculation with Heterodera glycines, transplanting after inoculation, type and amount of inoculum, and temperature were tested to determine the optimum procedure for the H. glycines race test. Numbers of H. glycines females extracted from plants in 7.5-cm-d pots tended to be higher than numbers from 10-cm-d pots, but not significantly so. Radicle lengths from 2.5 cm to 7.5 cm had no effect. Transplanting after inoculation reduced the variation in the number of females extracted, but the numbers of females produced were very low. Plump females (40 per pot) or eggs (4,000 per pot) were the best inocula. A constant temperature of 28 C appeared to be optimum. More H. glycines females were extracted from plants 28 days after inoculation than at 35 days. Race tests in which all of these factors were included were still highly variable in the number of H. glycines females extracted from different replications of the same test host. Tests of several susceptible cultivars revealed differences in their capabilities as hosts of H. glycines races.
Heterodera glycines; race test; soybean cyst nematode
The influence of selected plant species on egg hatch and subsequent development of Heterodera glycines race 3 was investigated. Plants tested included four soybean cultivars, red clover, alfalfa, hairy vetch, field corn, sweet corn, cabbage, tobacco, cotton, and wheat. Soybean stimulated egg hatching more than any of the other plant species, with H. glycines-resistant cultivars being more stimulating than susceptible ones. Hairy vetch also increased hatch. Roots of cabbage, red clover, alfalfa, and hairy vetch were readily penetrated by juveniles of H. glycines. Maturation to adult occurred only on soybean and hairy vetch.
Glycine max; hatch stimulation; Heterodera glycines; soybean; soybean cyst nematode
A nematicide, dibromochloropropane; the fungicides benomyl and maneb; an insecticide, oxydisulfoton; the herbicides trifluralin, linuron, and dinoseb; and fertilizers were applied to Heterodera glycines-infested soil. A resistant soybean cultivar alone produced the highest yield in one test, and its yield was not affected by application of pesticides or fertilizer. In two tests the cultivar that was supposed to be resistant was not. Application of nematicide alone resulted in higher yields of the susceptible cultivar, compared with the untreated check, in only one of three tests. Various combinations of pesticides also resulted in higher yields, and in all cases the nematicide was included. Pesticides and fertilizer must be used with discretion on soybean.
fertilizer; fungicide; Glycine max; herbicide; Heterodera glycines; insecticide; nematicide; soybean; soybean cyst nematode
Surveys from 1986 to 1988 identified 22 phytoparasitic nematode species in Arkansas cotton fields. Meloidogyne spp. was found in ca. 15% of the fields sampled. Of these samples ca. 33% were found to have a population density of 106/100 cm³ of soil or more. Rotylenchulus reniformis was found in high numbers (5,000 +/100 cm³ of soil) in 1% of the fields sampled in 1988. Heterodera glycines was found in ca. 22% of the samples, presumably because of past cropping to soybean. Other common species found were Pratylenchus alleni, P. brachyurus, P. scribneri, Tylenchorhynchus ewingi, T. goffarti, Quinisulcius acutus, Helicotylenchus dihystera, H. pseudorobustus, Hoplolaimus magnistylus, Paratrichodorus minor, and Xiphinema americanum. Paratylenchus spp. juveniles were found in ca. 10% of the samples; adults of P. projectus and P. tenuicaudatus were found in ca. 1% of the samples. Other species found only rarely were Pratylenchus zeae, Merlinius brevidens, T. martini, Helicotylenchus multicinctus, Scutellonema brachyurum, and X. chambersi.
Arkansas; cotton; crop loss estimate; Gossypium hirsutum; Helicotylenchus dihystera; Helicotylenchus pseudorobustus; Heterodera glycines; Hoplolaimus magnistylus; infestation estimate; Meloidogyne spp.; Merlinius brevidens; Paratrichodorus minor; Paratylenchus projectus; Paratylenchus tenuicaudatus; Pratylenchus alleni; Pratylenchus brachyurus; Pratylenchus scribneri; Pratylenchus zeae; Quinisulcius acutus; Scutellonema brachyurus; survey; Tylenchorhynchus ewingi; Tylenchorhynchus goffarti; Tylenchorhynchus martini; Xiphinema americanum; Xiphinema chambersi
In Arkansas wheat is commonly grown either in rotation or double cropped with soybean. Surveys from 1986 to 1988 identified 18 phytoparasitic nematode species in Arkansas wheat fields. The frequency of occurrence, as a percentage of the total number of samples (199), for the following nematodes was Heterodera glycines 43%, Quinisulcius acutus 40%, Pratylenchus scribneri 37%, Helicotylenchus pseudorobustus 15 %, Xiphinema americanum 14%, Paratylenchus tenuicaudatus 13 %, Pratylenchus alleni 10%, Merlinius brevidens 8%, Tylenchorhynchus ewingi 7%, Paratrichodorus minor 5%, T. martini 4%, and Hoplolaimus magnistyIus, Paratylenchus projectus, and juveniles of Meloidogyne spp. 2%. Helicotylenchus dihystera, Paratylenchus elachistus, and Tylenchorhynchus claytoni were each found in one wheat field.
Arkansas; crop loss estimate; Helicotylenchus pseudorobustus; Heterodera glycines; Hoplolaimus magnistylus; Meloidogyne spp.; Merlinius brevidens; infestation estimate; Paratrichodorus minor; Paratylenchus projectus; P. tenuicaudatus; Pratylenchus alleni; P. scribneri; P. zeae; Quinisulcius acutus; survey; Triticum aestivum; Tylenchorhynchus ewingi; T. martini; wheat; Xiphinema americanum
Soybean cultivars grown in pots in the greenhouse were tested for resistance by inoculation with Meloidogyne incognita or one of six races of Heterodera glycines. Selected cultivars were tested against each nematode isolate. The numbers of cultivars tested against each H. glycines race and the numbers resistant and (or) moderately resistant were as follows: Race 2 - 114 tested, 1 resistant and 9 moderately resistant; race 3 - 170 tested, 56 resistant and 17 moderately resistant; race 4 - 89 tested, 1 resistant and 13 moderately resistant; race 5 - 106 tested, 4 moderately resistant; race 6 - 95 tested, 10 resistant and 25 moderately resistant; race 14 - 81 tested, 2 resistant and 10 moderately resistant. No cultivar was resistant to all races. Meloidogyne incognita was tested on 139 cultivars; 50 were resistant.
Glycine max; Heterodera glycines; Meloidogyne incognita; race; root-knot nematode; soybean; soybean cyst nematode