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Abstract

The most appropriate use of fertilisers to offset damage caused by nematode infestations can benefit greatly from determining fertiliser use efficiency (FUE). FUE is defined as increase in host productivity and/or decrease in nematode population density in response to a given fertiliser treatment. This study describes new and integrated approaches to identify FUE in nematode-infected plants. In two consecutive experiments, Heterodera glycines-resistant 'Bryan', susceptible-tolerant 'G88-20092', and susceptible-intolerant 'Tracy M' soybean cultivars were inoculated with 0 or 15 000 eggs of Meloidogyne incognita or mixed stages of Pratylenchus penetrans per 800 cm3 of sandy loam soil and maintained under glasshouse conditions (28 ± 2°C) for 25 and 26 days. Plants received 83 ± 21 and 89 ± 19 ml either full-strength Hoagland solution (HS), HS without N (HS-N), or tap water daily in Experiments 1 and 2, respectively. Photosynthesis and nematode population dynamics were chosen to test FUE because the relationship between these two parameters, for the most part, determines the outcome of crop yield in the presence of nematodes. Although the FUE varied by fertiliser source, cultivar and nematode, the data were conclusive in identifying the interactions. FUE was high for photosynthesis in all three cultivars, and more so in HS than in HS-N. FUE was high for suppressing population densities of both nematodes and increasing photosynthesis in cv. Tracy M and for M. incognita in cv. G88-20092. Fertiliser application against P. penetrans in cv. Bryan was unproductive because nematode population density increased. FUE for P. penetrans in cv. G88-20092 and for M. incognita in cv. Bryan was less conclusive because there was some increase in nematode population density. Overall, these new approaches to identifying FUE for host productivity in the presence of nematodes provide quantitative data that should be of great interest to plant breeders, soil scientists, agronomists and plant protection specialists.

In: Nematology

Abstract

The effect of Heterodera glycines on H. glycines -resistant 'Bryan', susceptible-tolerant 'G88-20092', and susceptible-intolerant 'Tracy M' soybean cultivars grown in Hoagland solution (HS), HS without nitrogen (HS-N), or water treatments was studied for 25 to 26 days under greenhouse conditions (28 +/- 2 degrees C). Few of the 15 000 eggs per 800 cm3 soil infected 'Bryan' while 'G88-20092' and 'Tracy M' were severely infected, and photosynthesized and grew less in water and HS-N. Although less than the controls, photosynthetic rate in HS treatments was more than in water or HS-N. Nodulation was less in H. glycines than in the controls, and in HS than in water and HS-N treatments. However, more nitrogen was present in soil from HS than from HS-N or water treatments. Generally, cysts developed slower and had fewer eggs in HS followed by HS-N than in the water treatments. The results support the hypothesis that nematode infected plants do better under balanced nutrition than under nutrient deficient conditions. It is postulated that the slowed-down nematode development and/or diminished reproductive potential might be host-mediated. Effets de l'origine des elements nutritifs sur les mecanismes physiologiques des interactions entre Heterodera glycines et des genotypes de soja - L'effet d'Heterodera glycines sur les cultivars resistant "Bryan", susceptible-tolerant "G88-200092" et susceptible-non tolerant "Tracy M" cultives dans la solution d'Hoagland (HS), HS sans azote (HS-N) ou dans l'eau a ete etudie pendant 25 a 26 jours sous serre (28 +/- 2 degrees C). Quelques uns seulement des 15 000 oeufs par 800 cm3 de sol ont infeste le cultivar "Bryan" tandis que "G88-20092" et "Tracy M" ont ete severement infestes avec une photosynthese et une croissance plus faible pour les traitements eau et HS-N. Bien qu'inferieur a celui des temoins, le taux de photosynthese pour le traitement HS a ete plus eleve que pour les traitements eau et HS-N. De plus, la quantite d'azote presente dans le sol a ete plus elevee pour le traitement HS que pour les traitements HS-N ou eau. Generalement, les kystes se sont developpes plus lentement avec un nombre d'oeufs plus faible dans le traitement HS que pour les traitements HS-N et eau. Les resultats confirment l'hypothese selon laquelle les plantes infestees par le nematode se comportent mieux en conditions nutritives equilibrees qu'en conditions nutritives deficientes. Il est postule que le ralentissement du developpement du nematode et/ou la reduction de son potentiel reproducteur pourrait etre sous la dependance de l'hote.

In: Nematology

In addition to a limited number of commercially available cultivars, celery has least known status against plant-parasitic nematodes such as Meloidogyne hapla. The interactions of the cvs Dutchess and Green Bay, most widely used, and P-6848 Pybas and S-1355, new entries, and populations of M. hapla, Mh 1, Mh 2 and Mh 3, isolated from sandy/sandy loam soils, and Mh 4 and Mh 5, isolated from organic (muck) soil typical of celery production, were examined in a one nematode-generation glasshouse experiment. The tomato cv. Rutgers, a susceptible host on which the M. hapla populations were cultured, was used as a nematode viability control. Mh 5 followed by Mh 3 were the most infective of the populations of M. hapla. The celery cultivars ranged between 32% and 67% of the suitability of Rutgers tomato to M. hapla. In 3-month long experiments, inocula of 3500 and 9100 Mh 4 eggs (600 cm3 soil)−1 suppressed celery growth, suggesting the potential of these populations of M. hapla to cause yield loss. However, the varying degree of host suitability suggests that the severity of the problem will likely vary by cultivar and population of M. hapla. The study establishes numerical references for selecting cultivars and/or designing suitable location-specific management practices.

In: Nematology

Without resistant cultivars, conducive cropping systems and heterogeneous soils, managing parasitic variability of Meloidogyne hapla is a major challenge in carrot production. In glasshouse studies we tested a hypothesis that knowledge of carrot cultivars’ degrees of host suitability to populations of M. hapla could lead to developing site-specific management strategies. ‘Site-specific’ encompasses production practices, soil conditions and nematode problems. Interactions between the carrot cvs Abledo, Abundance, Enterprise, Eufora, Prodigy, Recoleta and Sugar Snax, and four M. hapla populations, Mh 1, Mh 2, Mh 3 and Mh 4, were examined. The tomato cv. Rutgers, in which the populations were cultured, was used as a nematode viability control. The first three populations were isolated from mineral soils and the fourth one from organic (muck) soil, all soils typical of carrot and other vegetable production in the US Midwest. While the reactions varied by population and by cultivar, the carrot cultivars proved to be hosts as suitable as, or more suitable than, cv. Rutgers tomato. All of the carrot cultivars were hosts as suitable as cv. Rutgers tomato to Mh 2, all but cv. Sugar Snax to Mh 3 and all but cvs Sugar Snax and Abundance to Mh 1. However, the Mh 3 infection levels in cv. Sugar Snax were as high as the Mh 2 infection levels. The cvs Sugar Snax and Abundance were the least suitable hosts for Mh 4 and Mh 1, and cv. Prodigy for Mh 4. The results suggest that identifying the reproductive potential of a resident M. hapla population is critical to making decisions about what carrot cultivars to plant as well as to minimise inoculum build-up in an infested field. The implications of the results across rotation crops are discussed.

In: Nematology

Abstract

The soybean cyst nematode (SCN), Heterodera glycines Ichinohe, cyst population densities at planting and at harvest have been related to soil texture but the seasonal mechanisms by which these correlations are established are less well known. The purpose of this work was to analyse the relationship of SCN life stages and reproductive potential (number of eggs per cyst) with soil texture. Cyst population density was positively correlated with sand and negatively correlated with clay and silt percentage in the soil within the ranges of 45-80% sand, 8-23% clay, and 8-43% silt in one field, but not in the other at five sampling times. The relationship between soil texture and juvenile stages in roots was weak. The stable relationship between SCN spatial and seasonal population dynamics and soil properties provides further support for potential delineation of management zones in SCN infested fields with a wide range of soil textures.

In: Nematology

Abstract

The objective of this work was to study the spatial distribution of the soybean cyst nematode (SCN), Heterodera glycines Ichinohe, in relation to soil fertility (pH, P+, K+, Ca2+, Mg2+ ), and soybean yield spatial patterns in relation to SCN, soil texture and soil fertility. SCN was positively cross-correlated with soil pH within a range of 60-130 m, and negatively cross-correlated with Ca2+ up to a range of 110 m in Field B; the correlation was weaker in Field A. Yield was negatively correlated with SCN. Yield was strongly cross-correlated with soil texture (r(sand)= –0.89, r(clay) = 0.84), soil pH (r = –0.60), and Ca2+ (r = 0.60) in Field B (range = 130-140 m). We conclude that management zone delineation would be an appropriate strategy to overcome yield losses in fields where soil properties and SCN densities appear spatially structured and where SCN and unfavourable soil conditions pose a strong influence on yield spatial variability.

In: Nematology

Abstract

Developing multi-purpose alternatives to synthetic nematicides for managing the northern root-knot nematode, Meloidogyne hapla, a problem in a variety of temperate vegetable and nursery crop production soils, continues to be challenging. Arugula (Eruca sativa), a high-end green vegetable crop with biofumigant and cover crop attributes, is an effective trap crop (dead-end host) for populations of M. hapla in sandy loam soil. Exploiting arugula's multi-purpose attributes, however, depends on understanding its interaction with M. hapla under a range of conditions. The objectives of this study were to determine if soil types affect: i) the ability of M. hapla to infect arugula; and ii) if M. hapla infection has any effect on arugula's vegetative quality in the respective soils. When 2-week-old arugula cv. Roquette seedlings were inoculated with either 0 (control), 4000 or 8000 M. hapla eggs per 300 cm3 of either sandy, sandy loam or muck soil, and maintained for 23 and 24 days (28±2°C), more nematodes were recovered from sandy loam soil. However, the numbers of nematodes recovered between the inocula were similar in the three soil types and nematode infection had no effect on plant growth or nutritional quality. However, the growth and leaf nutritional quantity of arugula were significantly affected by soil type. The results support the hypothesis that M. hapla will infect arugula in different soil types without affecting its vegetative quantity and quality, providing the basis for testing arugula's trap, vegetable and, possibly, biofumigant attributes from one seeding in fields where M. hapla exists.

In: Nematology

Abstract

The effect of soil pH 4.3, 4.6, and 5.9 on the pathogenicity of Heterodera glycines and Meloidogyne incognita on acid soiladapted soybean genotypes (Davis and PI 416937) was investigated in three glasshouse experiments over 28 days after inoculation with 0 or 1000 (Experiments 1 and 2) and 0 or 5000 (Experiment 3) second-stage juveniles. Although nematodes of both species infected both genotypes at all of the soil pH, the numbers decreased with decreasing soil pH. Both genotypes seem to be better hosts for M. incognita than for H. glycines, Davis more so than PI 416937. Both nematodes decreased shoot weight at high inoculum levels, indicating that H. glycines may be more pathogenic than M. incognita. Nematode development after infection of roots was not affected by soil pH or by genotypes. Overall, the results suggest that adaptation of these nematodes should be considered in breeding programmes to develop low pH tolerant soybean cultivars.

In: Nematology

Abstract

In the absence of resistant cultivars, the impending loss of methyl bromide (MBr) and few sustainable alternatives available, managing the northern root-knot nematode, Meloidogyne hapla, is a challenge in temperate vegetable and nursery production systems. Many brassica plants, including arugula, Eruca sativa, possess biofumigant and trap crop qualities, and thus have been gaining popularity as potential alternatives to MBr. As part of a project to develop alternatives to MBr, this study was conducted to determine the effects of arugula cv. Nemat on three glasshouse populations of M. hapla from Rhode Island (RI), New York, Geneva (NYG) and Michigan (MI). In two glasshouse experiments conducted at 20 ± 2°C and 28 ± 2°C, arugula and Rutgers tomato (standard susceptible) seedlings were inoculated with either 0 (control) or 3000 eggs of 67-85% undifferentiated stages of the three populations. Experiment 1 was terminated at 20 days and Experiment 2 at 28 days after nematode inoculation. At 20°C, 200 and 280 degree-days (DD, base 10°C) were accumulated, while 360 and 504 DD were accumulated at 28°C in the respective experiments. Total numbers of nematodes recovered from roots varied by host and by nematode population over the course of the study, but the numbers of females in roots did not vary significantly. This suggests variability in reaching the adult female stage. Egg and egg mass production was normal in all nematode-infected tomatoes, but no eggs were produced in more than 80% of arugula plants, and less than 17% of the arugula samples had fewer than five loose eggs and no egg masses. The results show that arugula interferes with development and reproduction of populations of M. hapla and thus has potential as a trap crop to control M. hapla.

In: Nematology

How soybean cyst nematode (SCN, Heterodera glycines) adapts when introduced into a new location under tillage, rotation and crop treatments is unknown. SCN race 3 (Hg Type 0) was introduced into a sandy loam field at more than 4000 eggs (100 cm3 soil)−1 and observed over 6 years under till and no-till, and either maize (Zea mays; C), SCN race 3 resistant soybean (Glycine max; R) or susceptible soybean (S) monocrop, or RCRC and SCSC rotations. While SCN population density was lower in no-till than in tilled treatments, and highest in S and lowest in C or RC rotations, it was detected at less than 1 cyst (100 cm3 soil)−1. This suggests a prolonged phase of decline from the introduced levels. The interaction effects of tillage, rotation and/or time on SCN suggest that outcomes vary by agronomic practice and time, providing agro-biologically-based understanding of SCN establishment in a new location.

In: Nematology