Evaluation of a Native and Introduced Isolate of Pochonia chlamydosporia against Meloidogyne javanica

Growth chamber and plastic tunnel experiments were conducted to compare the ability of a native and introduced isolate of Pochonia chlamydosporia to colonize the rhizosphere of selected plant species and survive in soil. Effects of the isolates on population density of Meloidogyne javanica and yield of tomato after single or multiple fungal applications were also determined. In growth chamber experiments, both isolates showed a similar ability to colonise the rhizosphere of selected vegetables, except for the introduced isolate, which produced more colony forming units cm^-2 of root surface on tomato and cabbage than the native one. In the tunnel house, both isolates parasitized eggs of M. javanica, and the native but not the introduced isolate increased parasitism after multiple applications. The native isolate was recovered more frequently from soil, and was a better colonizer of tomato roots than the introduced one irrespective of the number of fungal applications. Multiple fungal applications of either isolate reduced the nematode gall rating, and the native isolate also reduced the final egg population in roots. Neither isolates reduced final nematode densities in soil or affected tomato yield when compared to untreated plots.     

Interaction between Meloidogyne incognita and Pochonia chlamydosporia and their effects on the growth of Phaseolus vulgaris

An experiment was conducted to test the effect of different doses of 2, 4 and 8?g/2?kg of soil of Pochonia chlamydosporia against the root-knot nematode (Meloidogyne incognita) on Phaseolus vulgaris. It was observed that inoculation of plant with the nematode alone, and 15?days prior to fungal inoculation, reduced the plant growth when compared with the plant with fungal application followed by the nematode. Plant length, fresh and dry weight, chlorophyll, carotenoid, protein contents and nitrate reductase activity decreased in nematode-infested plants. Application of higher dose of 8?g/2?kg of soil of P. chlamydosporia increased all the plant growth parameters as well as biochemical parameters. Highest number of galls per root system was recorded on the plants infested with nematode but not treated with the fungus. However, application of fungus prior to nematode inoculation improved the plant growth and reduced the number of galls and the number of egg masses per root system.     

Evaluation of oil dispersion formulation of nematophagus fungus,Pochonia chlamydosporia against root-knot nematode,Meloidogyne incognita in cucumber

Root-knot nematode, Meloidogyne incognita is considered as one of the major non-insect pests of crops. The management of these root feeders becomes highly challenging due to a strong host-parasitic relationship. Pochonia chlamydosporia is a nematophagus fungus that colonizes eggs of nematodes. This study aimed to test the efficacy of P. chlamydosporia (NAIMCC-SF0039) against M. incognita. An oil dispersion formulation of P. chlamydosporia was prepared using emulsifiers and vegetable oil. This formulation had a shelf-life of 90 days (3.3 × 10⁸ CFU/mL) at room temperature (28 ± 1 °C). The inhibitory effect of oil formulation was tested against M. incognita by inoculating it on the egg mass. We found that colonization of the gelatinous matrix occurred on the third day of inoculation followed by complete egg parasitization on the seventh day. A greenhouse trial was laid out to evaluate the biocontrol potential of P. chlamydosporia in cucumber (Cucumis sativus). The results showed that the application of talc formulation of P. chlamydosporia at the rate of 1 kg per acre during planting, followed by delivery of 1 L of oil dispersion formulation through drip lines at 30-day intervals caused the highest reduction of nematode infestation. This treatment recorded 67.9 and 57.5% reduction in egg masses and soil nematode population respectively than that of control.     

Identification and molecular characterisation of new Mexican isolates of Pochonia chlamydosporia for the management of Meloidogyne spp.

New Mexican isolates of the nematophagous fungus Pochonia chlamydosporia were obtained from nematode infested fields in the vegetable growing area of Tepeaca Valley, Puebla State, Mexico. Based on macro and microscopic morphology, seven ‘putative’ P. chlamydosporia isolates were selected and the DNA extracted for polymerase chain reaction (PCR). Three new isolates of P. chlamydosporia were identified: Pcp2, Pcp21 and Pcp31. The amplification reaction of the internal transcribed spacer (ITS) region revealed a 650 bp amplicon which was used in a maximum likelihood phylogenetic inference analysis. Three groups were recovered in the tree topology, supported by a > 90% bootstrap value. Nucleotide identity values were > 83.6% between the test sequences and the reference sequence. In addition, using specific primers for two existing varieties of P. chlamydosporia, restriction fragment length polymorphism on the ITS products in conjunction with the phylogenetic inferences and the molecular test for detection of P. chlamydosporia vcp1 gene, it was found that all three isolates belong to a new variety which we have named P. chlamydosporia var. mexicana. We compared the chlamydospore production rate, rhizosphere colonisation and egg parasitism percentages of the three native isolates in Meloidogyne spp. with a reference isolate (Pc10). Native isolates produced > 1×10⁶ chlamydospores/50 g of substrate (of which more than 80% were viable), colonised > 80% of the rhizosphere, and parasitised > 60% of Meloidogyne incognita and Meloidogyne arenaria eggs. Meloidogyne hapla egg parasitism was < 60%. Isolates Pcp2 and Pcp21 were identified as potential biological control agents of Meloidogyne spp. to be tested further in greenhouse and field tests.     

Screening of tomato cultivars in the presence of the root-knot nematode,Meloidogyne javanica

In the present study, 12 varieties of tomato, viz., Arka Vikas, Damayanti, F-hybrid, Hybrid Padmarag, Hybrid Tripti, Marudam, Punjab chhoara, Pusa early dwarf, Punjab kesari, P.K.M.I, Roma and Pusa Ruby were screened for the presence of the root-knot nematode, M. javanica to obtain information on the varying degrees of resistances to tomato cultivars. All the cultivars of tomato tested were found to be infected with the root-knot nematode, M. javanica, however, to a varying extent. Consequently, there was a reduction in the growth parameters of cultivars leading to have an impact on the yield and quality of fruits. The cultivar, Marudam was found resistant while the cultivar the Pusa early dwarf was moderately resistant and rest of the 10 cultivars was highly susceptible.     

Measuring abundance,diversity and parasitic ability in two populations of the nematophagous fungus Pochonia chlamydosporia var. chlamydosporia

Abundance, genetic diversity and parasitic ability in the facultative nematode parasite Pochonia chlamydosporia var. chlamydosporia were compared in soils from two sites in Portugal under long-term tomato cultivation where root-knot nematodes (Meloidogyne sp.) were present. Fungal abundance assessed by selective agar or real-time quantitative PCR with specific primers was similar in both soils. PCR fingerprinting of isolates with ERIC primers indicated that the dominant P. c. var. chlamydosporia biotypes (profiles A and B) in both soils were very closely related, although a second biotype (profile C) was detected in one soil. When tomato plants infected with M. incognita were grown in the two soils, only profiles A and B were recovered from eggs. Primers based on polymorphisms in vcp1 demonstrated that isolates with profiles A and B were likely to prefer root-knot nematodes, whereas profile C preferred cyst nematodes. In the soil containing profiles A, B and C, egg parasitism by P. chlamydosporia was estimated at 1% using water agar plates with antibiotics but fewer than 0.2% of M. incognita eggs were shown to be infected with P. c. var. chlamydosporia when using species-specific β-tubulin-PCR primers. In contrast, the soil containing only profile B showed 22% egg parasitism on water agar plates and more than 2.5% of eggs were confirmed as P. c. var. chlamydosporia by species-specific β-tubulin-PCR primers. The results, which reveal limited diversity within the fungus at the two sites, are discussed in relation to biological control of plant-parasitic nematodes.     

Some isolates of the nematophagous fungus Pochonia chlamydosporia promote root growth and reduce flowering time of tomato

The fungal parasite of nematode eggs Pochonia chlamydosporia is also a root endophyte known to promote growth of some plants. In this study, we analysed the effect of nine P. chlamydosporia isolates from worldwide origin on tomato growth. Experiments were performed at different scales (Petri dish, growth chamber and greenhouse conditions) and developmental stages (seedlings, plantlets and plants). Seven P. chlamydosporia isolates significantly (P < 0.05) increased the number of secondary roots and six of those increased total weight of tomato seedlings. Six P. chlamydosporia isolates also increased root weight of tomato plantlets. Root colonisation varied between different isolates of this fungus. Again P. chlamydosporia significantly increased root growth of tomato plants under greenhouse conditions and reduced flowering and fruiting times (up to 5 and 12 days, respectively) versus uninoculated tomato plants. P. chlamydosporia increased mature fruit weight in tomato plants. The basis of the mechanisms for growth, flowering and yield promotion in tomato by the fungus are unknown. However, we found that P. chlamydosporia can produce Indole‐3‐acetic acid and solubilise mineral phosphate. These results suggest that plant hormones or nutrient ability could play an important role. Our results put forward the agronomic importance of P. chlamydosporia as biocontrol agent of plant parasitic nematodes with tomato growth promoting capabilities.     

A metabolomic approach to the study of wine micro-oxygenation

Wine micro-oxygenation is a globally used treatment and its effects were studied here by analysing by untargeted LC-MS the wine metabolomic fingerprint. Eight different procedural variations, marked by the addition of oxygen (four levels) and iron (two levels) were applied to Sangiovese wine, before and after malolactic fermentation. Data analysis using supervised and unsupervised multivariate methods highlighted some known candidate biomarkers, together with a number of metabolites which had never previously been considered as possible biomarkers for wine micro-oxygenation. Various pigments and tannins were identified among the known candidate biomarkers. Additional new information was obtained suggesting a correlation between oxygen doses and metal contents and changes in the concentration of primary metabolites such as arginine, proline, tryptophan and raffinose, and secondary metabolites such as succinic acid and xanthine. Based on these findings, new hypotheses regarding the formation and reactivity of wine pigment during micro-oxygenation have been proposed. This experiment highlights the feasibility of using unbiased, untargeted metabolomic fingerprinting to improve our understanding of wine chemistry.     

Assessment of three strategies for the management of Meloidogyne arenaria on carrot in Mexico using Pochonia chlamydosporia var. mexicana under greenhouse conditions

Three control strategies for management of Meloidogyne arenaria were evaluated on carrot under greenhouse conditions. The control strategies tested were: i) incorporation of fresh broccoli; ii) carbofuran (Furadan®); and iii) Pochonia chlamydosporia var. mexicana, isolate Pcp21. Each strategy was evaluated separately and in combination (16 treatment combinations), each with three replicates. The experiment was done between February and April 2014 and repeated over the same time period in 2015. Each replicate experimental unit consisted of a 1?kg pot filled with tyndallised soil, to which broccoli, fungus and carbofuran were added according to treatment. Carrot seeds were sown into each pot and inoculated with M. arenaria eggs according to treatment. Pots were then maintained in the glasshouse for 12 weeks at 25?±?5°C. After this time the fresh root weight, root length, percent reduction in root galling, P. chlamydosporia var. mexicana colony forming units (CFU)/g of soil, and CFU/g root were all measured. Results showed that isolate Pcp21 of P. chlamydosporia var. mexicana significantly reduced root galling percentage by 50 and 78% in 2014 and 2015, respectively. Application of the fungus in combination with broccoli or carbofuran also reduced root galling. The number of CFU/ g of soil or root remained the same over the 12 weeks of the experiment. This isolate of P. chlamydosporia significantly reduced damage caused by M. arenaria on carrot and is a promising agent for management of this nematode.     

Influence of organic additives on the incidence of root-knot nematode,Meloidogyne javanica in roots of tomato plants

Glasshouse experiment was conducted to assess the impact of green chopped leaves of four test plants (Lantana camara, Ficus virens, Kigelia pinnata and Ficus bengalensis) and two nematicides (Phorate and Carbofuran) on the plant growth parameters of tomato cv. K25 and on the root-knot development. Results revealed that all the tested treatments significantly (p = 0.05) improved plant growth parameters and reduced root-knot development compared to control. Among the tested organic additives, chopped green leaves of Lantana camara added to soil gave the highest enhancement in plant growth parameters, including plant height, fresh and dry weight, number of fruits and fruit weight with the values of 94.2 cm, 106.8 g, 31.6 g, 7.2 and 153.3 g respectively, as well as a greater reduction of Meloidogyne javanica reproduction and development but exhibiting a lower response compared to nematicides. There was also significant reduction in root-knot development in tomato plants growing in other organic additive amended soil.     

Bacillus halotolerans strain LYSX1-induced systemic resistance against the root-knot nematode Meloidogyne javanica in tomato

Purpose

Determination of the nematicidal potential and mode of action of bacteria isolated from tobacco rhizosphere soil against the root-knot nematode Meloidogyne javanica in tomato plants.

Methods

Antagonistic bacteria were isolated from rhizosphere soil of tobacco infested with root-knot nematodes. Culture filtrate was used to examine nematicidal activity and ovicidal action of bacterial strains. Biocontrol of M. javanica and growth of treated tomato plants were assessed in pot experiments. To clarify whether secondary metabolites of bacteria in tomato roots induced systemic resistance to M. javanica, bacterial culture supernatants and second-stage juvenile nematodes were applied to spatially separated tomato roots using a split-root system. Bacterial strains were identified by 16S rDNA and gyrB gene sequencing and phylogenetic analysis.

Results

Of the 15 bacterial strains isolated, four (LYSX1, LYSX2, LYSX3, and LYSX4) demonstrated nematicidal activity against second-stage juveniles of M. javanica, and strain LYSX1 showed the greatest antagonistic activity; there was dose-dependent variability in nematicidal activity and inhibition of egg mass hatching by strain LYSX1. In vivo application of LYSX1 to tomato seedlings decreased the number of egg masses and galls and increased the root and shoot fresh weight. Treatment of half of the split-root system with LYSX1 reduced nematode penetration to the other half by 41.64%. Strain LYSX1 was identified as Bacillus halotolerans.

Conclusion

Bacillus halotolerans LYSX1 is a potential microbe for the sustainable biocontrol of root-knot nematodes through induced systemic resistance in tomato.

     

Field assessment of efficacy of nitrogen salts to control the root-knot nematode (Meloidogyne javanica) on tomato

Influence of different nitrogen salts at electrical conductivity levels (EC2, 4 and 8?mmhos/cm) on tomato and root-knot nematode (Meloidogyne javanica) and their interactions was evaluated under field conditions. It was found that both diammonium phosphate ((NH₄)₂HPO₄) and ammonium sulphate ((NH₄)₂SO₄) were more effective than ammonium chloride (NH₄Cl) in causing an obvious suppression of M. javanica infection on tomato through reducing root galling and nematode reproduction and improving tomato growth and yield and their suppressive effect was similar to that of oxamyl or ethoprophos. At higher ECs, the tested nitrogen salts did not greatly affect pH, EC and salinity of rhizospheric soil except NH₄Cl at EC8 that caused higher EC and salinity over the untreated control which makes NH₄Cl less suitable candidate. Therefore, the use of (NH₄)₂HPO₄ and (NH₄)₂SO₄ alone or in combination with other control measures could control M. javanica and improve the growth and yield of tomato under field conditions.     

Role of cyanide production by Pseudomonas fluorescens CHA0 in the suppression of root-knot nematode, Meloidogyne javanica in tomato

Summary Pseudomonas fluorescens strain CHA0 produces hydrogen cyanide (HCN), a secondary metabolite that accounts largely for the biocontrol ability of this strain. In this study, we examined the role of HCN production by CHA0 as an antagonistic factor that contributes to biocontrol of Meloidogyne javanica, the root-knot nematode, in situ. Culture filtrate of CHA0, resulting from 1/10-strength nutrient broth yeast extract medium amended with glycine, inhibited egg hatch and caused mortality of M. javanica juveniles in vitro. The bacterium cultured under high oxygen-tension conditions exhibited better inhibitory effects towards nematodes, compared to its cultivation under excess oxygen situation. Growth medium amended with 0.50 or 1.0 mM FeEDDHA further improved hatch inhibition and nematicidal activity of the strain CHA0. Strain CHA77, an HCN-negative mutant, failed to exert such toxic effects, and in this strain, antinematode activity was not influenced by culture conditions. Exogenous cyanide also inhibited egg hatch and caused mortality of M. javanica juveniles in vitro. Strains CHA0 or CHA77 applied in unsterilized sandy-loam soil as drench, caused marked suppression of root-knot disease development incited by M. javanica in tomato seedlings. However, efficacy of CHA77 was noticeably lower compared to its wild type counterpart CHA0. An increased bioavailability of iron following EDTA application in soil substantially improved nematode biocontrol potential of CHA0 but not that of CHA77. Soil infestation with M. javanica eggs resulted in significantly lower nematode population densities and root-knot disease compared to the juveniles used as root-knot disease-inducing agents. Strain CHA0 significantly suppressed nematode populations and inhibited galling in tomato roots grown in soil inoculated with eggs or juveniles and treated with or without EDTA. Strain CHA0 exhibited greater biocontrol potential in soil inoculated with eggs and treated with EDTA. To demonstrate that HCN synthesis by the strain CHA0 acts as the inducing agent of systemic resistance in tomato, efficacy of the strain CHA0 was compared with CHA77 in a split root trial. The split-root experiment, guaranteeing a spatial separation of the inducing agent and the challenging pathogen, showed that HCN production by CHA0 is not crucial in the induction of systemic resistance in tomato against M. javanica, because the HCN-negative-mutant CHA77 induced the same level of resistance as the wild type but exogenous cyanide in the form of KCN failed to trigger the resistance reaction. In the root section where both nematode and the bacterium were present, strain CHA0 reduced nematode penetration to a greater extent than CHA77, suggesting that for effective control of M. javanica, a direct contact between HCN-producing CHA0 and the nematode is essential.     

In vitro water stress bioassays with the nematophagous fungus Pochonia chlamydosporia: Effects on growth and parasitism

The biocontrol potential of Pochonia chlamydosporia, a fungus with parasitic activity against economically important plant-parasitic nematodes, can be influenced by abiotic factors such as water availability. The objective of this study was to evaluate the effects of different water stress regimes on in vitro growth, sporulation, germination and parasitism of P. chlamydosporia isolates. The osmotic water potential of 1.7% corn meal agar (CMA) was modified by addition of potassium chloride (KCl) or glycerol, and the matric water potential was modified using polyethylene glycol (PEG 8000). The fungus was able to grow over a range of potentials but radial growth rates decreased with the increase of osmotic and matric stress. No growth was observed at −10 MPa on 1.7% CMA amended with glycerol and at −7.1 MPa on medium with PEG 8000 but all isolates were able to resume growth when transferred onto unmodified 1.7% CMA. The production of chlamydospores was repressed in both osmotic and matric modified media. Although the production of conidia increased in medium modified with KCl, the germination rate was lower. Spores/hyphal fragments remained viable in all isolates that were previously inoculated onto media with growth-limiting water potential (−10 MPa on 1.7% CMA amended with glycerol and −10 MPa on medium with PEG 8000). The percentage of viable conidia produced on 1.7% CMA, after inoculation under osmotic or matric stress conditions for 25 days, was over 74.5% in all isolates (osmotic stress) and ranged from 1% (Pc1) to 65.8% (Pc280) (matric stress). The in vitro infection of potato cyst nematodes, Globodera rostochiensis eggs by P. chlamydosporia isolates, grown under these limiting conditions, was studied using a standard bioassay. The percentage of parasitized eggs was significantly higher under osmotic stress except for isolates Pc2 and Pc3. P. chlamydosporia spores/hyphal fragments can remain viable at water potentials limiting for growth, for prolonged periods of time, suggesting that the osmoregulation mechanisms, used to compensate water stress, affect in vitro sporulation and increased pathogenicity. Knowledge on water requirements of P. chlamydosporia enables a better understanding of its survival and growth strategies in the soil environment and could aid the development of effective strategies to increase the production and quality of inoculum, thus contributing to the implementation of biosafe, sustainable management strategies against plant-parasitic nematodes.     

Identification of resistance to Meloidogyne javanica in the Lycopersicon peruvianum complex

Clones of Lycopersicon peruvianum PI 2704352R2, PI 270435-3MH and PI 126443-1MH expressed novel resistance to three Mi-avirulent M. javanica isolates in greenhouse experiments. Clones from PI 126443-1MH were resistant to the three M. javanica isolates at 25°C. The three isolates were able to reproduce on one embryorescue hybrid of PI 126443-1MH, but not on three L. peruvianum-L. esculentum bridge-line hybrids of PI 1264431MH when screened at 25°C (Mi-expressed temperature). Clones of PI 270435-2R2 and all its hybrids with susceptible genotypes were resistant to the three M. javanica isolates at 25°C. The bridge-line hybrid EPP-2xPI 2704352R2 was susceptible to M. javanica isolate 811 at 32°C, whereas PI 270435-2R2 and all other hybrids of PI 27043 5-2R2 crossed with susceptible genotypes were resistant at 32°C. At 32°C, one F₂ progeny of PI 126443-IMHxEPP-1, and three test-cross progenies of PI 1264409MHx[PI 270435-3MHxPI 126443-1MH], and reciprocal test-cross progenies of [PI 270435-3MHxPI 2704352R2]xPI 126440-9MH, each segregated into resistant: susceptible (RS) ratios close to 31. The results from the F₂ progeny indicated that heat-stable resistance to Mi-avirulent M. javanica in PI 126443 -1MH is conferred by a single dominant gene. The results from the test-crosses indicated that this gene in PI 126443-1MH is different from the resistance gene in PI 270435-3MH. The resistance gene in PI 270435-3MH was also shown to differ from the resistance factor in PI 270435-2R2. The expression of differential susceptibility and resistance to M. javanica and M. incognita in individual plants of the bridge-line hybrid, embryo-rescue hybrid, F₂, and test-crosses indicated that at least some genes governing resistance to M. javanica differ from the genes conferring resistance to M. incognita. A new source of heat-stable resistance to M. javanica was identified in Lycopersicon chilense.     

Inheritance of resistance to the root-knot nematode Meloidogyne javanica in lettuce

Resistance to the root-knot nematodes Meloidogyne spp. would be a valuable attribute of lettuce Lactuca sativa L. cultivars grown in tropical regions. The looseleaf lettuce 'Grand Rapids' is resistant to both M. incognita and M. javanica. Resistance to M. incognita has a high heritability, under the control of a single gene locus, in which the 'Grand Rapids' allele, responsible for resistance (Me), has predominantly additive gene action, and has incomplete penetrance and variable expressivity. We studied the inheritance of the resistance of 'Grand Rapids' (P(2)) to M. javanica in a cross with a standard nematode-susceptible cultivar Regina-71 (P(1)). F(1)(Regina-71 x Grand Rapids) and F(2) seed were obtained, and the F(2) inoculated, along with the parental cultivars, with a known isolate of M. javanica to evaluate nematode resistance. A high broad sense heritability estimate (0.798) was obtained for gall indices. Class distributions of gall indices for generations P(1), P(2), and F(2) were in agreement with theoretical distributions based on a monogenic inheritance model for the range of assumed degrees of dominance between approximately -0.20 and 0.20. M. javanica resistance appears to be under control of a single gene locus, with predominantly additive gene action. Whether or not the Grand Rapids allele imparting resistance to M. javanica is the same Me allele imparting resistance to M. incognita remains to be determined.     

Occurrence of Meloidogyne spp. in Cerrado Vegetations and Reaction of Native Plants to Meloidogyne javanica

The Cerrado biome represents a hotspot of biodiversity. Despite this, the nematofauna in this biome has not been well characterized, especially that related to root‐knot nematodes. This work aimed to identify Meloidogyne species present in different cerrado vegetations and to investigate potential hosts of Meloidogyne javanica in this biome. Soil samples (250) were collected in native areas of cerrado vegetation located at the National Park of Brasília (PNB) (125 samples) and Água Limpa Farm (FAL) (125 samples), and transferred to sterile pots. Single tomato plants cv. Santa Clara (susceptible) were transplanted into individual pots and maintained for 90 days under glasshouse. Females of Meloidogyne spp. were extracted from tomato roots and identified based upon esterase phenotypes and confirmed with PCR using specific sequence characterized amplified regions (SCAR) primers. Native plants were inoculated with 10 000 individuals (eggs + J2) of a pure culture of M. javanica and maintained under glasshouse for 6 months. From the 250 samples collected, 57 (22.8%) presented Meloidogyne spp. A total of 66 Meloidogyne populations were identified as follows: M. javanica (75.76%), M. incognita (10.60%), M. hapla (9.1%), M. morocciensis (3.03%) and M. arenaria (1.51%). The following esterase phenotypes were detected: M. javanica (J3 and J2), M. incognita (I1 and I2), M. hapla (H1), M. morocciensis (A3) and M. arenaria (A2). The SCAR primers incK14F/incK14R, Fjav/Rjav and Fh/Rh amplified specific fragments in M. incognita (399 bp), M. javanica (670 bp) and M. hapla (610 bp) and can be used for identification of indigenous Meloidogyne spp. from cerrado. The primer set Far/Rar is not specific for M. arenaria due to the amplification of DNA in M. morocciensis. Mimosa caesalpiniifolia was the only native plant in which M. javanica developed a high reproductive rate, and it is probably a host for this nematode in cerrado.     

Effects of nitrogen fertilisers on the Javanese root-knot nematode Meloidogyne javanica and its interaction with cucumber

The influence of different nitrogen salts at five electrical conductivity levels (EC 2, 4, 6 and 8 mmhos/cm) on the Javanese root-knot nematode (RKN) (Meloidogyne javanica) and its interaction with cucumber was evaluated under in vitro, growth chamber and greenhouse conditions. Percentages of egg-hatching and second-stage juvenile viability of M. javanica were greatly reduced when NH₄Cl, (NH4)₂SO₄ and NH₄NO₃ were used especially at the higher levels of EC and accompanied with reduction in cucumber root galling. The lower root galling (less than 2.5) was accompanied with NH₄Cl, (NH₄)₂SO₄ and (NH₄)₂HPO₄, while KNO₃ and NH₄NO₃ resulted in moderate root galling. In contrast to the nitrogen salts, NaCl caused a reduction in both nematode infection and root growth especially at higher EC levels and this could be due to salinity effect. Diammonium phosphate was superior over the tested salts in increasing plant and root fresh and dry weights and cucumber phosphorus content, while KNO₃ was superior in increasing in plant content of potassium.