Abstract: The burrowing nematode, Radopholus similis (Cobb.) Thorne, causes the most damage to bananas. To minimize nematicide applications, cropping systems that use fallow, crop rotation and clean planting material have been developed in the French West Indies. In order to optimize the benefit of the intercropping period, we studied the survivorship of R. similis in different soil types and conditions. We monitored the survivorship of calibrated populations of R. similis in the laboratory on a Nitisol and on an Andosol, two soils derived from volcanic ashes and pumices. We studied water potentials ranging from 0 to -700 kPa on undisturbed soil and on soil previously frozen to get rid of living nematodes. Mortality of adult R. similis decreased regularly, and was fairly well described by Teissier's model. In the previously frozen soils, R. similis survived longer in wet soils (half-life of 21-46 days at 0 to -5 kPa) than in dry soils (half-life of less than 10 days between -80 and -250 kPa). In contrast, in undisturbed soils, R. similis survived longer in dry soils: half-lives ranged from 57 days at -273 kPa to 17 days at water saturation in the Andosol, and 36 days at -660 kPa to 14 days at water saturation in the Nitisol. These results are consistent with the absence of anhydrobiosis in R. similis, unlike Pratylenchus coffeae. A coffeae survivorship curves over time do not follow a model derived from exponential decrease like Teissier's model. These results also show that the recommended one year host-free period required to sanitize soils cannot be shortened without risk, even if flooding the soil could improve it. (C) 2009 Elsevier B.V. All rights reserved.
Abstract: The stability and positive functions (such as pest regulation) of intensively managed agroecosystems can be enhanced by increasing biodiversity (in particular, by introducing cover plants or associated crops). Therefore, understanding modes of interspecific interactions among the phytophagous species, such as coexistence via host-plant partitioning, may allow manipulation of the balance between pest and non-pest species. In the present study, we tested the hypothesis that a community of six plant-feeding nematode species in banana agroecosystems is structured by host plants. This was done using extensive data on the abundance of the different nematodes species on banana and associated weeds in Martinique. Because the purpose of this study was to focus on host-plant range, we eliminated the effects of temperature, rainfall, and soil type using a partial canonical correspondence analysis. Host plants in banana agroecosystems have a marked influence on the plant-feeding nematode community structure. Host plants allow niche partitioning between some but not all pairs of species. The most evident pattern is the niche partitioning among the three nematodes considered long established in Martinique. For pairs of species showing no host-plant niche partitioning, additional information regarding the colonisation and population dynamics over time both at the root and agroecosystem scale would allow better understanding of the equilibrium among species of the plant-feeding nematode community. For management purposes, the modification of abundance of some host plants, which could be used as cover plants in the field, could change the balance among nematode species. (C) 2009 Elsevier Ltd. All rights reserved.
Abstract: To minimize application of nernaticides in banana fields, crop systems have been developed in the French West Indies that combine fallow or rotation crops and nematode-free in vitro plants. After two to four years, populations of the burrowing nematode Radopholus similis have developed enough to cause economic losses, leading banana growers to use nematicides. To understand how banana fields are recontaminated, we studied the dissemination of R. similis by water flow. At a 1-m scale, we analyzed the dispersion of R. similis under a rainfall simulator: we isolated a 1-m(2) study plot, placed a R. similis suspension on the upstream soil surface, and simulated a 60 mm/h rainfall for 72 min. We collected soil samples every 10 cm downstream after 12 min of rainfall, and subsequently at 20-min intervals, and extracted the nematodes using a Seinhorst elutriator and then a Baermarm funnel. our results showed that the nematode dissemination follows an inverse exponential law, and depends more on soil moisture at the beginning of rainfall than on the length of rainfall: in fresh soil, 69-80% of the R. similis recovered were found less than 10 cm downstream from the nematode inoculation line, whereas in wetted soil, 76-85% of the recovered individuals were collected in the outlet tub located downstream from the apparatus. This passive dissemination model partially explains the distance covered by individual nematodes but not the low percentage of motile nematodes recovered in the outlet tub (10% and 36% in fresh and wet soils) compared to the percentage of motile nematodes found in the soil (80% and 84% in fresh and wet soils). Indeed, water runoff is likely to disseminate R. similis over long distances only when soil moisture is close to field capacity. (C) 2008 Elsevier B.V. All rights reserved.
Abstract: Banana hybrids with resistance to Yellow Sigatoka and Black Leaf Streak disease were evaluated for resistance to the burrowing nematode Radopholus similis and to the lesion nematode Pratylenchus coVeae in a growth chamber at 24-28. Plants produced by tissue culture were acclimatised for 6 weeks prior to inoculation. Forty-five days after inoculation with nematodes, the root systems were processed and nematode numbers assessed. Two cultivars of Grande Naine (Musa AAA, Cavendish subgroup, ITC1256 and cv902) and one cultivar of Yangambi Km5 (Musa AAA, Ibota subgroup, ITC1123) were used respectively as susceptible and resistant controls. Results based on multiplication rates and root infestations showed that three of these hybrids (FB918, FB919 and FB924) were not significantly different from the resistant control Yangambi Km5 with a lower multiplication of R. similis. Similarly four of these hybrids (FB918, FB919, FB920, FB924) showed a lower multiplication of P. coffeae, not significantly different from the same resistant control. This is the first study that shows a partial resistance to both nematode species, R. similis and P. coffeae within synthetic hybrids of M. acuminata, adding an important extra value to these dessert banana hybrids formerly bred to resist to Mycosphaerella leaf spot diseases.
Abstract: Bananas cultivated for export all belong to Cavendish cultivars and are all recognized as very susceptible to nematodes, particularly to the burrowing nematode Radopholus similis and the lesion nematode Pratylenchus coffeae. Even if there have been many changes in the management of banana nematodes in large commercial banana plantations, chemical control still remains most often the last resort method to manage the nematodes, although the number of registered products is definitely declining. Therefore, nematode control though genetic improvement is gaining new interest worldwide. In this study, 55 banana accessions mostly diploids from the Musa acuminata genome group (AA) but including some triploid accessions (AAA), some diploids of the Musa balbisiana genome group (BB) and some interspecific hybrids (AAB, AB) were evaluated for resistance to four nematode species R. similis, P. coffeae, Meloidogyne incognita and M. arenaria. These experiments were conducted in a growth chamber under controlled conditions. All banana accessions were susceptible to nematode species, although many different levels of susceptibility were detected. This study confirmed the good resistance status to R. similis of some cultivars from the Pisang jari buaya and Pisang batuau subgroups and the partial resistance of 17 diploid accessions significantly different from the susceptible reference cv. Grande Naine. This study also showed that 12 diploid accessions exhibited a partial resistance to P. coffeae, including some usual or potential genitors belonging to the wild diploids subspecies burmannica (cvs. Long Tavoy 1 and 2) and burmannicoides (cv. Calcutta 4). No source of resistance to Meloidogyne spp. was found. These screening results, combining for the first time four nematode species, are discussed within the scope of banana breeding in order to produce parental diploid lines with single or combined nematode resistances and further develop triploids that can substitute existing susceptible commercial cultivars.
Abstract: The synthetic banana hybrid FB920 (Musa spp., AAA group) has been designed to be resistant to Sigatoka and Black Leaf Streak Diseases, caused respectively by Mycosphaerella musicola and Mycosphaerella fijiensis. In addition to these features, the hybrids seem less susceptible to plant-parasitic nematodes, especially the burrowing nematodes (Radopholus similis) and the lesion nematode (Pratylenchus coffeae) than classic Cavendish cultivars, such as Williams, Grande Naine, or Poyo. This genetic modification drastically reduces pesticide use. Herein, we used the SIMBA model (a model to simulate phenology, growth, and plant-parasitic nematode/banana interactions) to examine the population dynamics of plant-parasitic nematodes in cropping systems with hybrid FB920 in various initial conditions. Results from field observations and simulations show that in the long-term, the spiral nematodes (Helicotylenchus multicinctus) can overtake the burrowing nematodes and that nematode populations are smaller than in Cavendish banana fields. This reduced capacity of FB920 to support multiplication of R. similis reduces the use of pesticides and thus re-creates favourable conditions for fauna, thereby increasing the global sustainability and resilience of banana agro-ecosystems. (C) 2008 Elsevier Ltd. All rights reserved.
Abstract: During the last decade, new crop systems have been developed in the French West Indies to avoid repeated applications of nematicides in banana fields. These combine fallow or rotation crops and nematode-free in vitro plants. In many fields, however, after 2-4 years, the burrowing nematodes Radopholus similis progressively re-infest banana fields, leading growers to re-apply nematicides. Among different hypotheses for re-infestation, we studied the possibility that nematodes were disseminated by runoff water. The study was conducted in an experimental field on plots that were defined by ditches or marked with flags and weeded or not, prior to replanting with in vitro plants. Results showed that 50-80cm deep ditches efficiently prevent R. similis dissemination and that dispersion by water runoff is the major route of contamination. In contrast, weed management during the fallow period had little influence. (C) 2008 Elsevier Ltd. All rights reserved.
Abstract: New crop systems have been developed in the French West Indies that combine fallow or rotation crops with nematode-free vitro-plants to avoid the massive application of nematicides in banana fields. In these new banana fields, recontamination by the burrowing nematode Radopholus similis can then happen either by run-off or irrigation water. To understand these phenomena, we studied the vertical dissemination of R. similis by water leaching using soil cylinders and rainfall simulations. Steel drums were used to collect cylinders of soil (around 14.3 dm(3)) with a backhoe. The soil cylinders were placed in an aspersion chamber, saturated with water, and a R. similis suspension was placed on the soil surface. Afterwards, rainfalls ranging from 12 to 540 mm were simulated. Nematodes were then extracted from different soil layers (0-5 to 20-25 cm depth) using either (i) a Seinhorst elutriator followed by a Baermann funnel or (ii) centrifugation-flotation combined with Meldola blue staining. Results showed that dissemination of R. similis at the scale of the decimetre in nitisoil is limited: less than 8% of the applied nematodes reached layers deeper than 10 cm after exceptional rainfalls that represent several times the poral volume of the soil. Dissemination below 25 cm depth seemed to be limited to very few individuals, from 0.1 to 0.2%. Among leached nematodes, the percentage of non-active and dead nematodes increased significantly with depth. It seems that R. similis have developed a behaviour to escape leaching. These findings question the generally accepted idea that water dissemination of plant-parasitic nematodes is mainly a passive phenomenon. (C) 2008 Elsevier B.V. All rights reserved.
Abstract: During a survey of the nematodes associated with weeds in banana fields in Martinique, 41 weed species in 37 genera from 20 plant families were collected to extract nematodes from the roots. Results of this survey showed that 24 weed species were hosts of Radopholus similis, 23 were hosts of Helicotylenchus spp., 13 were hosts of Pratylenchus spp., 13 were hosts of Hoplolaimus seinhorsti, 29 were hosts of Meloidogyne spp. and 24 were hosts of Rotylenchulus reniformis. The presence of the burrowing nematode was more consistently found within three families, the Euphorbiaceae, Poaceae and Solanaceae. In some weed species such as Caladium bicolor, Commelina diffusa, Echinochloa colona and Phenax sonneratii, the levels of nematodes recovered were similar to, or greater than the numbers recovered from Musa roots. These results clearly show that certain weeds can be significant reservoirs of plant parasitic nematodes including R. similis in banana fields. This information is crucial in devising appropriate nematode control measures for use with rotation crops or fallow before re-planting banana fields with nematode free planting material. (c) 2005 Elsevier Ltd. All rights reserved.
Abstract: Ninety-six isolates of Meloidogyne species collected front banana fields from Martinique, Guadeloupe, and French Guiana, were examined using esterase (Est) and malate dehydrogenase (Mdh) phenotypes. Adult females identified as M. arenaria, M. incognita, M.javanica, M. cruciani, H hislpanica, and Meloidogyne sp. showed species-specific phenotypes only for the esterase enzymes. Intraspecific variability among isolates of M. arenaria, M. inctgnita, and M. javanica was detected using Est and Mdh. Perineal patterns were used as a complementary tool together with enzyme characterization and were essential for checking the morphological consistency of the identification. The major species of M. arenaria and M. incognita were detected at 61.9% and 34.3% of the total number of isolates, respectively, and the other minor species at 3.8%. The mixed Meloidgyne species were detected in 45.1% of the samples. Genetic analysis was conducted using RAPD markers, which alone or in combination provided reliable polymorphisms both between and within species. RAPD analysis of the data resulted in clustering of species and isolates Congruent with esterase phenotype characterization. The intraspecific variability in M. incognita and in M. arenaria represented 14.9% and 61.6% of the amplified polymorphic fragments, respectively. This high level of variation in M. arenaria isolates may indicate multiple origins for populations classified as M. arenaria or more than one species inside the same group, but more detailed morphological and DNA studies will be necessary to test this hypothesis.
Abstract: The ready to use formulation of oxamyl Vydate (R) 24 L is one of the last three nemadaticides currently used in Martinique. This formulation causes two major safety problems: an unfavorable toxicological profile (very toxic) and a highly flammable formulation, therefore hazardous to store. A new formulation diluted and without flammable solvent, was developed. This paper presents the results of two trials for the assessment of effectiveness of both oxamyl formulations against main nematodes attacking banana plants in Martinique, especially Radopholus similis and the banana black weevil Cosmopolites sordidus. Two tests were carried out to compare the new formulation with the usual formulation, a reference program (rotation of several nematicides: cadusafos, aldicarb, fosthiazate and fenamifos) and an untreated control. Both formulations provided R. similis and Helicotylenchus multicinctus temporary controls similar to the reference nematicide program and limited yield losses. On the other hand, their efficiency against Cosmopotiles sordidus appeared insufficient.
Abstract: Esterase phenotypes were used to characterise 25 populations of Meloidogyne spp. collected on bananas from different banana producing areas in Brazil, using a simplified technique for routine analysis. Meloidogyne javanica, M. incognita, M. arenaria, and Meloidogyne spp. were detected at percentages of 61.7, 32.2, 4.3 and 1.8, respectively. The Meloidogyne populations represented mixed species in 80% of the samples, M. javanica and M. incognita prevailing under field conditions. Genetic analyses were conducted using RAPID markers which provided, alone or in combination, reliable polymorphisms both between and within species. Based on the presence or absence of bands, RAPID analysis of the data resulted in clustering of species and isolates congruent with esterase phenotype characterisation. The intraspecific variability in M. jamnica, M. incognita and M. arenaria represented 29.1, 19.5 and 40.2% of the polymorphic amplified fragments, respectively. A general lack of correlation was observed between banana cultivar group, geographical origin and differentiation of the nematodes.
Abstract: Nematode control in the large commercial banana plantations is currently based on the application of two to four nematicide treatments per year. These repeated pesticide applications lead to many drawbacks in terms of toxicity both for the applicators and for the environment. In Martinique (French West Indies) during the last 10 year, an alternative culture system based on the previous cleanup of lands contaminated by plant-parasitic nematodes (mainly the burrowing nematode Radopholus similis), by way of either a fallow period or an appropriate crop rotation before planting with nematode-free banana vitroplants, has been set up. However, a simple natural fallow period is often not sufficient to eliminate the burrowing nematodes and to clean the land properly. Several factors have to be considered, such as the efficiency of the destruction of the old banana plants and the evolution of the flora susceptible to R. similis. In this study, we compared the chemical destruction of banana plants by an injection of glyphosate in the pseudo-stems to the usual mechanical destruction using a spading-machine. The application of this technique strongly improved the benefits of the successive fallow (only 12.2% of R. similis infested plants compared to 76% after mechanical destruction) with a gain of 14% and 29% (first and second production cycle) of output in ton per hectare with no application of nematicide. (C) 2002 Elsevier Science Ltd. All rights reserved.
Abstract: The orientation of juveniles of Meloidogyne incognita and Rotylenchulus reniformis was studied in salt gradients created in a linear agarose gel. Twelve combinations of calcium, potassium, sodium or ammonium cations and chloride, nitrate or sulphate anions were tested. The orientation of juveniles of M. incognita was induced by the constitutive cation of the salt, e.g., calcium salts had no effect while the other salts and especially ammonium salts and ammonium nitrate were strongly repellent. In contrast, the orientation of juveniles of R. reniformis was induced by the constitutive anion of the salt, e.g., chloride salts were found to be repellent while sulphate and nitrate salts were attractive. These results are discussed as possible novel control strategies for economically important plant parasitic nematodes. In other respects, these differences in chemical preferences may partly explain the observed geographical distribution of these nematode species according to the ionic content of the soils.
Abstract: The effectiveness of fosthiazate (Nemathorin((R)) 10G) was evaluated on bananas against plant-parasitic nematodes and black weevil, Cosmopolites sordidus, in four field trials in Martinique. In the first trial, two rates of fosthiazate (2.0 and 3.0 g a.i./mat) were compared with aldicarb (Temik((R)) 10G), applied at 2.0 g a.i./mat. In the three other studies, fosthiazate, at 1.5 and 2.0 g a.i./mat applied 3 times per year, was compared with alternate applications of 3 reference nematicides: cadusafos (3.0 g a.i./mat), aldicarb (2.0 g a.i./mat) and fenamifos (3.0 g a.i./mat). A non treated check was included in all 4 experiments. Trials 3 and 4 had high levels of weevil so a standard insecticide vs. banana weevil, fipronil (0.2 g a.i./mat), was applied on the check plots. The burrowing nematode, Radopholus similis, was the dominant nematode species, followed by the spiral nematode Helicotylenchus multicinctus in trials 1, 3 and 4 whereas root-knot nematodes, Meloidogyne spp., dominated the nematofauna in trial 2 and were present at all sites. The lance nematode, Hoplolaimus seinhorsti, was only important on trial 2. Fosthiazate was as effective as the standard nematicides in trials 1 and 2 and significantly more effective in trials 3 and 4 against the burrowing nematode, R. similis. Few differences were observed in the control of H. multicinctus whereas both rates of fosthiazate significantly reduced infection by Meloidogyne spp. and H. seinhorsti. Fosthiazate was as effective against C. sordidus as fipronil. Fosthiazate treatments increased banana yields up to 35% compared to check plots by preventing toppling-over.
Abstract: Hirschmanniella caribbeana sp. n. is described and figured from mangrove vegetation from Guadeloupe. Females are characterised by the tail terminus having two lateral peg-like projections with a smaller, irregular intermediate projection, a low, rounded lip region with five to six annuli, a 17-20 mu m long stylet, areolated lateral fields, intestine not overlapping the rectum and phasmids situated at midtail. Males numerous, similar to females except for sexual characters. Juvenile tail ends in a single, thin, pointed mucro. Notes, morphometrics, descriptions and figures are given for Pratylenchus, P. jordanensis, P. teres and P. loosi all new records for this region.
Abstract: The population dynamics of Meloidogyne incognita juveniles (J2) in association with the parasite Pasteuria penetrans was studied in a field in Martinique. Data obtained at three-week intervals for one year were analyzed to study the relationship between J2 density and endospore infestation levels. Six crop sequences were evaluated in five replicates. They were: resistant tomato-okra-fallow-cabbage; susceptible tomato-okra-fallow-cabbage; bean-pepper-fallow-cabbage; eggplant-fallow; cucumber-velvetbean-fallow-cabbage; fallow-pepper-cabbage-fallow-cabbage. The J2 densities showed fluctuating trends, frequently synchronous with fluctuations of endospore infestation. The highest J2 numbers observed ranged between 1 000 and 1 500 nematodes/100 g of soil in the first four crop sequences, and between 150 and 250 J2/100 g of soil in the last two. The highest percentages of nematodes with adhering endospores ranged between 50 and 70%. The resistant tomato crop showed a sharp decrease in the nematode density at the end of the crop sequence, with a similar synchronous decrease of the endospore infestation. This bend was also observed during the fallow periods in the other treatments. Susceptible crops allowed a sharp increase of the J2 densities. During these periods of population growth, the concomitant increase of the endospore infestation levels was interrupted with fast growing J2 densities. In the last two crop sequences, the J2 densities progressively decreased because of the non-host status of velvetbean and of a longer fallow, respectively. When all the pooled data from the six treatments were considered, a significant linear correlation was observed between J2 densities and the corresponding endospore infestation values (P < 0.001). This relationship appeared related to the density of females releasing J2 and/or endospores in the soil. All pooled mean densities also followed the Gutenberg-Richter power law distribution, indicating the occurrence of chaotic effects influencing their dynamics. Although chaos implies non-predictability of 52 numbers and endospore infestation dynamics, it also suggests that large-scale fluctuations may induce local nematode suppression by P. penetrans.
Abstract: Enzyme phenotypes, specifically esterases (EST), malate dehydrogenase (MDH), superoxide dismutase (SOD) and glutamate-oxaloacetate transaminase (GOT) were used to characterise different species of Meloidogyne, mostly from Brazil and from some American countries. Esterase activity was highly polymorphic and was the most useful in the identification of the different species. Using this enzyme it is possible to characterise and identify the four major species: M. javanica, M. incognita, M. arenaria and M. hapla from a large collection of 111 populations of Meloidogyne.,le spp. Another seven less common species (M. coffeicola, M. paranensis, M. konaensis, M. exigua, M, graminicola, M. oryzae, M. mayaguensis), with only one or a few populations of each, were studied and exhibited species-specific EST phenotypes. The two enzymes (EST and MDH) differentiated M. graminicola and M. oryzae. It was possible to detect atypical (unidentified) phenotypes: three fr om Brazil, one from the USA and another from Chile. The minor bands of esterase profits provided information to detect intraspecific variability among some populations of M, incognita and six populations of M. exigua. Profiles of MDH permitted separation of two isolates of M. javanica a from Brazil.
Abstract: Resistance to bacterial wilt, caused by Ralstonia solanacearum, in tomato lines CRA 66 and Caraibo is reported to be decreased by root-knot nematode galling and by introduction of the Mi gene for nematode resistance. The Mi gene is located on tomato chromosome 6, which also carries a major quantitative trait locus (QTL) for resistance to bacterial wilt. Bacterial wilt resistance was evaluated in FS-progenies derived from two crosses between near-isogenic lines, Caraibo x Carmido and CRA 66 x Cranita, differing for small and large introgressions from Lycopersicon peruvianum that carry the Mi gene, respectively. These introgressed regions were mapped using RFLP markers. Plants homozygous Mi(+)/Mi(+) (susceptible to the nematode) and homozygous Mi/Mi (resistant) for the Mi gene were selected in F2 and used to produce F3 progenies. Parents and F3-lines with Mi/Mi had resistance to bacterial wilt reduced by 30% in Caraibo x Carmido and by 15% in CRA 66 x Cranita. Caraibo and Carmido were demonstrated to be isolines and the small introgression from L. peruvianum resulted in loss of the QTL for bacterial wilt resistance, which is probably allelic or linked in repulsion to the Mi gene. In contrast, resistance to bacterial wilt segregated in the F3 lines from the cross CRA 66 x Cranita, giving families varying in resistance between the levels shown by the parents. Consequently, two hypotheses were considered: (i) after only four backcrosses, the parents were not isolines and the genes for resistance to bacterial wilt from CRA 66 were still segregating, and (ii) the parents were isolines and variation in resistance to bacterial wilt in F3 was due to recombination events among the large L. peruvianum introgressed chromosome region from Cranita.
Abstract: The soil-borne bacterial pathogen Ralstonia solanncearum commonly coexists with polyspecific nematode populations in tropical and subtropical areas. The wounding of roots by nematodes is usually invoked to explain the correlation between nematode infection and bacterial wilt, since this wounding increases the number of sites for bacterial entry. Bacterial wilt development on tomato was investigated in a controlled environment on the susceptible tomato cultivar Floradel and the polygenically wilt-resistant cultivar Caraibo. The bacterial isolate GMI 8217 and two different sedentary plant parasitic nematodes, the endoparasitic root-knot nematode, Meloidogyne incognita, and semi-endoparasitic reniform nematode, Rotylenchulus reniformis, were cross-infected. At low temperatures (22-27 degrees C), the bacterium GMI 8217 was slightly pathogenic on all tomato lines, except on Floradel coinfected by root-knot nematode. At high temperatures (27-32 degrees C), the root-knot nematode greatly increased wilt severity in susceptible Floradel and resistant Caraibo, but the reniform nematode had no such effect regardless of temperature x cultivar combination. This showed that infection of tomato roots by root-knot nematodes reduced genetic resistance to bacterial wilt. The effects of combining bacterial wilt resistance with the Mi gene for resistance to root-knot nematode (Mi, resistant; Mi(+), susceptible) was investigated using the near-isogenic lines Caraibo (Mi(+)/Mi(+))/Carmido (Mi/Mi) and CRA66 (Mi(+)/Mi(+))/Cranita (Mi/Mi), which differ by the size of the segment of L. peruvianum DNA carrying the Mi gene. The presence of the Mi gene was associated with a marked decrease in bacterial wilt resistance. It is suggested that at least one gene governing part of the bacterial wilt resistance is closely linked or allelic to the Mi gene in the tomato lines used in this experiment.
Abstract: The relationships between soil nematodes and soil texture, carbon content and depth were assessed in both a cultivated and uncultivated plots. Simple correlation coefficient analyses indicated a negative linear correlation between the plant-parasitic species Helicotyienchus retusus Siddiqui and Brown and soil clay content in the uncultivated site. However, Mantel rests showed this correlation to be spurious and only due to the presence of a common spatial pattern in the variables distribution. Both H. retusus density and soil clay content appeared to be independently driven by a common, unknown cause. The us: of suitable statistical methods to analyse spatially dependent variables proved to be particularly fruitful in that they prevent spurious correlations and allow us to test different causal models involving the set of variables at hand.
Abstract: This article presents the results of surveys conducted in Guyane and Martinique during 1994/1995. Seven species of Xiphinema (X. americanum sensu lato, X. basiri, X. clavicaudatum, X. costaricense, X. filicaudatum labratum, X. longicaudatum, and X. oryzae) are briefly described and illustrated. X. basiri and X. longicaudatum are described for the first time from South America. Three new Xiphinema species are described: Xiphinema labiosum n. sp. is characterised by peri-oral ring, small, crescent-shaped amphid aperture, lip region almost continuous with body outline, and weakly curved to almost straight habitus. Xiphinema pseudokrugi n. sp. is characterised by incomplete anterior reproductive branch, vulva situated almost at mid-body, slight cuticular ornamentations anterior and posterior of vulva, and a convex-conoid tail with a rounded or slightly bulging terminus. Xiphinema seinhorsti n. sp. is characterised by long, offset, caudal, finger-like projection on the ventral side of the tail, presence of a blind canal at the tail terminus, long odontostyle, and uterus with Z-differentiation consisting of a small number of granular bodies. (C) Orstom/Elsevier, Paris.
Abstract: Two experiments were conducted in 1994 in Martinique to compare the efficacy of short-term rotations on the population decline of Meloidogyne incognita and Rotylenchulus reniformis associated with vegetables and various plants. Tomato, weeds, Tagetes erecta, Mucuna pruriens cv. utilis or Brachiaria decumbens were grown, or soil was left in clean fallow, for a three-month period just before planting a crop of lettuce. For M. incognita, the greatest population decline was observed after M. pruriens and T. erecta (87% for both crops), while R, reniformis declined most after M. pruriens (86%). The leguminous forage plant, M. pruriens exhibited the best vegetative growth, soil coverage and weed competivity. The use of M. pruriens cv. utilis as a rotation crop may provide a practical and environmentally safe means for growers to suppress population densities of both M. incognita and R. reniformis prior to the cultivation of susceptible short-term vegetable crops.
Abstract: Redescriptions are given for Mesocriconema surinamense (De Ghisse & Maas, 1970) Loof & De Grisse, 1989, associated with Dicorynia guianensis Amshoff and Rotylenchus caudaphasmidius Sher, 1965 associated with a species of Aspidosperma Martins & Zuccharini in a French Guiana rain forest. These are new records for that country. Males of M. surinamense are described for the first time and are characterized by a squared labial disc and a comparatively small bursa. Discocriconemella heynsi Van den Berg & Marais, 1995 is proposed as a synonym of M. surinamense. Discocriconemella limitanea (Luc, 1959) De Grisse & Loof, 1965 is reported from soil around D. guianensis.
Abstract: During a survey of ornamental plants conducted in Martinique in 1992, 498 soil and root samples were collected from ornamental plant species belonging to 3 families. the Araceae, Zingiberaceae and Strelitziaceae, a further 50 root samples were taken from Anthurium grown in artificial substrates. 27 plant-parasitic nematode species belonging to Is genera were found, including one new species, Criconemoides ornativulvatus and two new records for Martinique viz. Helicotylenchus pseudorobustus and Monotrichodorus sacchari. Nematode populations differed with the different ornamentals but Rotylenchulus reniformis was the dominant species in all the soils. Except for a few single species of Trichodoridae, Criconematidae, Longidoridae and Tylenchulidae certain species were dominant on certain plants, e.g. Meloidogyne spp. on Ginger Lilies, Radopholus similis on Anthurium, Aorolaimus luci on Red Torch Ginger and Pratylenchus coffeae on Alocasia. The possible damages of these plant-parasitic species to flower cultivation and production is discussed.
Abstract: A recent survey of plant-feeding nematodes associated with seedlings of the forest tree Dicorynia guianensis Amshoff in a primary rain forest near Paracou, French Guiana yielded twenty-one species belonging to fourteen genera and one species of an unidentified genus of the Heteroderinae. This plant feeding nematode population which make up only 7.6% of the total nematode fauna is characterized by i) a high species diversity and equitability and ii) adaptations to feeding on lignous plants, such as having long or robust stylets. The predominant ectoparasites were eight Xiphinema and a Monotrichodorus species. The predominant endoparasites, extracted from the soil, root mats and seedling roots, were juveniles of an unidentified species belonging to the Heteroderinae, juveniles of Trophotylenchulus clavicaudatus (Colbran, 1966) Cohn & Kaplan, 1983 and a semi-endoparasite, Aorolaimus holdemani Sher, 1964. All these genera are serious parasites of cultivated plants and trees, especially in the seedling stage. For the first time the possible importance of nematodes in seedling mortality and natural regeneration of a forest tree species was shown in a primary tropical rain forest in South America. Our results of great nematode diversity, are similar to those from other tropical rain forests wordlwide.
Abstract: The spatial pattern of four species of plant-parasitic nematodes in a sugarcane crop in Martinique was analysed using geostatistics. Aggregation of populations was first described with the variance to mean ratio and Morisita's index. The indices showed that nematodes had clumped distributions. Geostatistical analysis demonstrated that the nematode data were autocorrelated and allowed a fine description of the species density patterns. Correspondence analysis was used to ordinate the data and showed the presence of an antagonism between Criconemella onoensis and the other species. A cross semi-variogram indicated a negative cross correlation between the pattern of Criconemella onoensis and the pattern of the sum of the other species present at the study site.
Abstract: This study reports on the distribution of nematodes in different soil habitats under a permanent pasture of digitgrass (Digitaria decumbens Stent. cv. 'Pangola') in Martinique. The objectives were (i) to evaluate a gentle fractionation method compatible with further soil nematode extraction and (ii) to assess the respective soil microhabitats of plant-feeding nematodes and free-living nematodes. This study indicated that gentle soil fractionation can effectively separate soil habitats and allow the recovery of associated nematodes. Plant-feeding nematodes were equally distributed between inter-aggregate pores, habitats constituted of aggregated fine silt + clay particles and roots + rhizosphere, Most of free-living nematodes (53%) resided in inter-aggregate pores. Irrespective of the food resource, densities of nematodes (number per gram of habitat) were similar in habitats coarser than 1000 mu m (A5000, A2000, and A1000), Habitats with the finest soil (A200) were not favourable sites because of the rarity of roots (for plant-feeding nematodes) and physical constraints.
Abstract: Paratrichodorus caribbensis n. sp. from a primary rain forest Martinique is described and illustrated. The new species, known from the female only, is characterized by a medium-sized onchiostyle (37-41 mu m), the far posterior position of the vulva (V = 60-64%), comma-shaped vaginal sclerotizations and the absence of caudal pores. Morphometric data is given for Allotrichodorus westindicus (Rodriguez-Montessoro et al., 1978) Rashid et al., 1986 from French Guiana and Monotrichodorus sacchari Baujard and Germani, 1985 from French Guiana and Martinique.
Abstract: This study compares the microdistribution of plant-parasitic nematodes and sugarcane roots in relation to the row and some soil parameters on a ferrisol characterized by three degrees of hillock levelling. Soil and root samples were collected on a grid located between two rows of sugarcane. In the most levelled location, where carbon, nitrogen and potassium contents were the poorest, Pratylenchus zeae presented a spatial pattern related to the row. This was also observed with Helicotylenchus erythrinae in the three locations. On the contrary, Criconemella onoensis did not show a marked spatial pattern related to the row or root quantity in any of the situations. Hemicriconemoides cocophillus appeared to be distributed parallel to sugarcane rows in the direction of the slope. Spatial patterns were figured by graphical displays and analyzed using semi-variograms to confirm and characterize the observed patterns. The use of cross semi-variograms showed antagonistic distributions between C. onoensis and the other species which were more prominent in the levelled locations. In respect to hillock levelling intensity leading to variations of soil parameters, micro-spatial patterns and interactions among plant parasitic nematodes vary quantitatively and qualitatively.
Abstract: Helicotylenchus macrostylus n. sp. is characterized by body length (853-1150 mu m in females and 811-964 mu m in males), stylet length (42-45 mu m in females), tail length (13-24 mu m in females and 20-27 mu m in males), and posterior position of the excretory pore (179-211 mu m from front in females). Helicotylenchus dihystera (Cobb, 1893) Sher, 1961, H. erythrinae (Zimmermann, 1904) Golden, 1956, and H. pseudorobustus (Steiner, 1914) Golden, 1956 are new records for French Guiana. Morphometric data are given for these 3 species.
Abstract: Ogma toparti sp, n. is described and figured from Martinique, Females are characterized by 47 to 52 retrorse body annuli with twelve longitudinal rows of scales at midbody which are more irregularly spaced on dorsal side of body, reticulate pattern on cuticula, one lip annulus which is smaller than first body annulus, a 56 to 66 mu m long stylet and scalloped vulval lips. A key to those Ogma species with twelve longitudinal rows of scales is given. Criconema longulum Gunhold, 1953 and Paratylenchus coronatus Colbran, 1965 are reported from Guadaloupe for the first time.
Abstract: During a survey of the nematodes associated with weeds in vegetables growing in plastic polytunnels in Martinique, 33 weed species in 26 genera and 15 families were collected to extract nematodes from the roots. Results of this survey showed that-weeds mainly belong to five families: the Asteraceae, Amaranthaceae, Poaceae, Euphorbiaceae, and the Portulacaceae and only four phytoparasitic nematode genera were consistently recovered. Four weed species were found to be nematode free. All the others were considered nematode reservoirs. The most frequently encountered nematodes were Rotylenchulus reniformis, followed by different species of Meloidogyne, Helicotylenchus, and Pratylenchus. When present, root infestation by Meloidogyne:ne always outnumbered the other nematode species. It is noticeable that, during this survey, only three weed species exhibited typical symptoms of galls and deformed roots when infected by Meloidogyne.
Abstract: Of the weeds that were found in banana production areas, only Asystasia gangetica was parasitised by Radopholus similis; Helicotylenchus multicinctus and Hoplolaimus pararobustus were able to parasitise all weed species. Field trials were carried out in Cote d'Ivoire to assess the potential for using nematode-free micro-propagated banana plants following cultural and chemical methods for nematode control. Banana (Musa acuminata) cv. Poyo was examined for nematodes after weed fallow, flooding and chemical treatment. Before replanting bananas, nematode assays showed that: i) all nematode species declined but were not eliminated after a 1,3-dichloropropene soil treatment; ii) H. multicinctus, H. pararobustus and Cephalenchus emarginatus were still present after either a 2-year weed fallow (dominated by Chromolaena odorata or Asystasia gangetica) or a 1O-week flooding; iii) R. similis did not persist after fallowing or flooding. All nematode species were found in plots treated with 1,3-dichloropropene and that had been planted with bullheads, suckers or nematode-free micropropagated plants. After both fallow and flooding, R. similis was reintroduced on infested planting materials (bullheads and suckers) even when they were pre-treated with a nematicide. When fallow and flooded plots were planted with nematode-free materials (vitro-plants), R. similis did not appear in the roots for two vegetative cycles. The other species, still present in the soil, invaded the roots and increased slowly in numbers. These results were confirmed in commercial banana plantations.
Abstract: During the growth of yam in Martinique, Scutellonema bradys develops successively in the seed tuber and the roots which constitute the intermediate focus of infection and finally in the neo-tuber. However, the highest rate of multiplication of the nematode was observed in the tuber after harvest. The adult females transfer the infection from the seed to the newly formed parts. The time of abundant multiplication of the nematode seems to correspond with the appearance of the necrotic areas and coincides with the initiation of the dormancy (and therefore the interruption of the respiration) of the tuber. The weight loss of an infested tuber reached approximately 30% whereas an uninfested one loses only 10%.
Abstract: Criconemoides ornativulvatus sp. n. is described and figured from Martinique. Females are characterized by the presence of three lip annuli, enlarged submedian pseudolips which give rise to indistinctive submedian lobes, a low labial area and a non-raised labial disc resulting in a head form appearing rounded, 82 to 90 retrorse body annuli with smooth to irregular margins, a sharply pointed tail with last three to four annuli drawn out, an open vulva with prominent projections of various forms on anterior lip, a slightly sigmoid vagina and a 71 to 88 mu m long stylet.
Abstract: In Cote d'Ivoire, most of the dessert bananas for export are produced in intensive agrosystems on large plantations. The use of fumigant nematicides. recently succeeded by non-fumigants for the control of Radopholus similis, the burrowing nematode and other species. has led farmers to rely only on nematicides for efficicnt protection against plant-parasitic nematodes. However, because of an increase in both production costs and environmental concerns, future research is now directed towards development of 'integrated pest management' strategies that would reduce inputs of pesticides and rationalize their use. From this standpoint, the measures to be used in the intensive banana agrosystems against plant-parasitic nematodes should for the first time be applicable to other banana agrosystems. Based on the understanding of the environment, of the host plant and of the biology of the plant-parasitic nematodes, many practices can be deployed to control nematode damage, whatever the technical capacity of farmers. These practices should lead to a shift from nematode control to nematode management Strategies on bananas by considering banana plants more as individual entities of a banana orchard than a homogeneous field, especially in established plantations.
Abstract: Spatial arrangement of nematodes in soil and roots around the banana plant and its relation to interspecific interaction phenomena have been studied through the results of field experiments conducted in banana plantations in the Ivory Coast. The attractiveness of Radopholus similis towards the banana roots seems to be governed by the rhizogenic activity of some parts of the rhizome rather than by the strict origin of the roots on the rhizome. In the absence (or reduced densities) of one or more competitors, R. similis is able to colonize, with high population levels, the entire set of banana roots. In the presence of competitors, e.g. Helicotylenchus multicinctus, the arrangement and density of R. similis, in the soil as in the roots, is reduced and restricted to areas close to the rhizome. The higher the density of competitors, the more restricted the dispersion area of R. similis around the rhizome. Notions of ecological "niche" and "sub-niche" are discussed and applied to the nematodes-banana root system interaction, within the hypothesis of the succession of nematode species in a competitive hierarchy theory.
