Effect of amino acids on root-knot nematode (Meloidogyne javanica) infecting tomato plant

Six amino acids viz. DL-methionine, DL-valine, DL-serine, DL-phenylalanine, L-proline and L-histidine were tested against root knot of tomato caused by Meloidogyne javanica. All amino acids showed significant response in plant growth characters with corresponding reduction in the number of galls, adult females, egg masses and juvenile stages within the treated plants. DL-phenylalanine gave significantly higher response in reducing the hatch of egg masses and survival of juveniles in in vitro test compared to control. The highest plant growth and maximum reduction of galling incidence of tomato were recorded in the DL-phenylalanine- treated plants followed by L-proline and L-histidine. All the amino acids gave positive response in suppressing the development of the nematode in the treated plants.     

Biological control of root-knot nematode (Meloidogyne javanica) disease by Pseudomonas fluorescens (Chao)

Plant growth-promoting Rhizobacteria is currently developed as an biocontrol agent against many plant pathogens. In this research, biological control of root-knot nematode (Meloidogyne javanica) by Pseudomonas fluorescens was investigated in greenhouse and laboratory experiments. Results showed that 10⁹?(CFU/ml) of P. fluorescens decreased nematode infection and other parameters significantly, compared to the control. P. fluorescens was able to cause destruction of nematode egg mass matrix and significantly decreased nematode egg hatching level. Specific activities of resistance-related enzymes, namely peroxidase (POX) and phenylalanine ammonia lyase (PAL), increased significantly in P. fluorescens-inoculated plants. Maximum activities of POX and PAL were observed at the 5?days after inoculation, respectively. Results suggested that the destruction of eggs and plant defence mechanisms leading to systemic resistance are two main suppression mechanisms used by P. fluorescens against nematode.     

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.     

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.     

Biological control of root-knot nematode,Meloidogyne incognita infesting tomato

Talc based formulations of two antagonistic fungi, Acremonium strictum W. Gams and Aspergillus terreus Thom were tested separately and together for their ability to suppress the development of root-knot disease of tomato caused by the root-knot nematode, Meloidogyne incognita Kofoid & White in two consecutive trials (2007–08). Tomato seedlings were each inoculated with M. incognita at 2 infective second stage juveniles /g of soil. M. incognita caused up to 48% reduction in plant growth parameters compared to un-inoculated control. Control efficacy achieved by combined soil application of both fungi, in terms of galls/root system and soil population/50 ml of soil, was 66 and 69% respectively at 60 days of inoculation compared to control. Soil application by individual fungus did not achieve as much effectiveness as the biocontrol agents applied together. The combined treatment was found to have antagonistic effect on M. incognita development and increased plant vigor. Incorporation of fine powder of chickpea pod waste with talc powder was beneficial in providing additional nutrients to both plant and biocontrol agents and increased the activity of the nematophagous fungi in soil. A. strictum and A. terreus were successfully established in the rhizosphere of tomato plants up to the termination of the experiment.     

Evaluation of pomegranate (Punica granatum L. var. Gabsi) peel extract for control of root-knot nematode Meloidogyne javanica on tomato

The present study was carried out to assess the nematicidal potential of Punica granatum L. against the root-knot nematode Meloidogyne javanica responsible for yield losses in tomato. Varied concentrations of methanolic, ethanolic and aqueous extracts from pomegranate peels were investigated for activity against eggs and juveniles of M. javanica in in vitro assays. All extracts used significantly inhibited egg hatch by over than 75%, but viability of second-stage juveniles (J2) was not significantly inhibited by ethanolic extract. Aqueous extract was assessed at the concentration of 10, 25 and 50% against M. javanica on tomato in greenhouse trials; pomegranate peels powder was also tested at the rate of 3, 6 and 9 g as a soil amendment. Both extracts significantly reduced nematode infestations; aqueous extract enhanced plant growth but powder amendment exhibited a phytotoxicity compared to the untreated plants. The reduction in number of galls, egg masses and nematode reproduction rate was recorded.     

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.     

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.     

Effect of opportunistic fungi on the life cycle of the root-knot nematode ( Meloidogyne javanica) on brinjal

The effect of four opportunistic fungi viz., Paecilomyces lilacinus, Cladosporium oxysporum, Gliocladium virens and Talaromyces flavus on the life cycle of the root-knot nematode, Meloidogyne javanica, on brinjal was evaluated under glasshouse conditions. The results revealed that these fungi affected the penetration and development of M. javanica. The life cycle of M. javanica was delayed by 10, 7, 4 and 2 days in the presence of P. lilacinus, C. oxysporum, G. virens and T. flavus respectively. Fecundity, number of eggs per eggmass and number of larvae was also reduced in the presence of these opportunistic fungi. However, the number of males increased in the presence of opportunistic fungi.     

Mycorrhizal fungi and Pseudomonas fluorescens application reduces root-knot nematode (Meloidogyne javanica) infestation in eggplant

Eggplant cultivation is subjected to attacks by numbers of pests and diseases from the nursery stage until harvest. Root-knot nematode (M. javanica) is one of the most significant restrictions in the successful cultivation of eggplant as it damages the crop year-round. One of the most essential classes of plant symbionts is arbuscular mycorrhizal fungi (AMF) and phosphate solubilizing bacteria (PSB), which significantly impact plant development, feeding, disease tolerance, and resistance to M. javanica. Eggplant seedlings were inoculated with two mycorrhizal fungi, Glomus mosseae (Gm) and Gigaspora gigantea (Gg), together with the phosphate-solubilizing bacteria (PSB) Pseudomonas fluorescens (Pf; ATCC-17400) under the presence of nematodes inoculation of Meloidogyne javanica as 1000 eggs of M. javanica in each pot. Observations were recorded for 9 morphological traits, 6 fruit morphometric traits using Tomato Analyzer (version 4) software program, and 4 fruit biochemical traits. Along with the data recorded for mycorrhization (%), number of galls and reaction to RKN. Plants inoculated with the consortium (Pf + Gm + Gg) performed substantially better for most traits. Furthermore, the eggplant plants treated with consortium developed the highest levels of fruit biochemical content along with the highest level of mycorrhization (68.20%). Except for certain fruit morphometric traits, the treatment containing Pf + Gg outperformed the treatment containing Pf + Gm. Overall, this research showed that AM fungi could be a sustainable solution to the eggplant RKN problem.     

Effect of Nodularia harveyana biomass on the incidence of root-knot nematode (Meloidogyne incognita) in tomato

An acetone extract of Nodularia harveyana wasshown to be toxic to the free-living nematode Cephaloboides oxycerca. This antagonistic effect wastested in pot culture trials with lyophilized biomasson gall induction by the root-knot nematode Meloidogyne incognita, using different methods ofapplication of the cyanobacterial biomass to thetomato plants. The trials revealed a possibleutilization of biomass of this cyanobacterium as aprotection agent against this phytoparasite.     

Effects of some plant extracts on larval hatch of the root-knot nematode,Meloidogyne incognita

Abstract

The inhibitory effect of water extract of seed, leaf and bark of five plants, viz., Tamarindus indica, Cassia siamea, Isoberlinia doka, Dolnix regia and Cassia sieberiana was evaluated on larval hatch of Meloidogyne incognita in the laboratory. All the plant parts inhibited larval hatch of M. incoginta Percentage inhibition was higher in the seeds followed by the leaves and bark. Degree of inhibition observed, was directly related to the concentration of the extract. The standard suspensions inhibited hatching by about 97% while dilutions of S/100 inhibited larval hatch by 3%. Nematicidal activity of the plant parts of the five plants showed that C. siamea was the most effective followed by C. sieberiana, I. doka, T. indica and D. regia.     

Biocontrol of root-knot nematode Meloidogyne incognita by the isolates of Bacillus on tomato

Fifteen isolates of Bacillus, isolated from the root-knot nematode suppressive soils, were used for the biocontrol of Meloidogyne incognita on tomato. Bacillus isolates B1, B4, B5 and B11 caused greater inhibitory effect on hatching of M. incognita than caused by other isolates. In addition, these isolates (B1, B4, B5 and B11) caused greater colonisation of tomato roots and also caused greater increase in the growth of tomato seedling than caused by other isolates. All the isolates of Bacillus were able to increase growth of tomato and caused reduction in galling and nematode multiplication in green house tests. Isolates B1, B4, B5 and B11 caused a greater increase in growth of tomato and higher reduction in galling and nematode multiplication than other isolates in a green house test. These isolates were also tested for hydrogen cyanide (HCN) and indole acetic acid productions. Only one isolate (B13) produced HCN out of 15 tested. On the other hand, isolates B5, B11, B4 and B1 showed greater production of IAA than the other 11 isolates tested. This study suggests that Bacillus isolates B5, B11, B4 and B1 may be used for the biocontrol of M. incognita on tomato.     

Biocontrol of root-knot nematode Meloidogyne incognita by the isolates of Pseudomonas on tomato

Biocontrol of root-knot nematode Meloidogyne incognita was studied on tomato using 15 isolates of fluorescent Pseudomonads isolated from pathogen suppressive soils. Pseudomonas aeruginosa (isolates Pa8, Pa9 and Pa3) caused greater inhibitory effect on hatching of M. incognita than other isolates. In addition, isolates Pa8, Pa9 and Pa3 caused greater colonisation of tomato roots and also caused a greater increase in the growth of tomato seedlings. These isolates also caused a greater increase in growth of tomato and higher reduction in galling and nematode multiplication in a green house test than is caused by other isolates. Isolates Pf1, Pf5, Pf6 and Pa13 were unable to increase growth of tomato and caused less reduction in galling and nematode multiplication compared to other isolates. Only 10 isolates produced siderophores on chromo-azurol sulfonate (CAS) agar medium and isolate Pa12 showed greater production of siderophore followed by Pa11, Pa9, Pf10, Pa3 and Pf5. Similarly, isolates Pa14, Pa12, Pf10, Pa9, Pa8, Pa7 and Pa6 produced greater amount of HCN than the other isolates tested. Isolates Pa8 and Pa9 showed greater production of IAA than the other 13 isolates tested. This study suggests that P. aeruginosa isolates Pa8 and Pa9 may be used for the biocontrol of M. incognita on tomato.     

RAPD linkage map of the genomic region encompassing the root-knot nematode (Meloidogyne javanica) resistance locus in carrot

Inheritance studies have indicated that resistance to the root-knot nematode (Meloidogyne javanica) in carrot inbred line ’Brasilia-1252’ is controlled by the action of one or two (duplicated) dominant gene(s) located at a single genomic region (designated the Mj-1 locus). A systematic search for randomly amplified polymorphic DNA (RAPD) markers linked to Mj-1 was carried out using bulked segregant analysis (BSA). Altogether 1000 ten-mer primers were screened with 69.1% displaying scorable amplicons. A total of approximately 2400 RAPD bands were examined. Four reproducible markers (OP-C2₁₇₀₀, OP-Q6₅₀₀, OP-U12₇₀₀, and OP-AL15₅₀₀) were identified, in coupling-phase linkage, flanking the Mj-1 region. The genetic distances between RAPD markers and the Mj-1 locus, estimated using an F₂ progeny of 412 individuals from ’Brasilia 1252’×’B6274’, ranged from 0.8 to 5.7 cM . The two closest flanking markers (OP-Q6₅₀₀ and OP-AL15₅₀₀) encompassed a region of 2.7 cM . The frequency of these RAPD loci was evaluated in 121 accessions of a broad-based carrot germplasm collection. Only five entries (all resistant to M. javanica and genetically related to ’Brasilia 1252’) exhibited the simultaneous presence of all four markers. An advanced line derived from the same cross, susceptible to M. javanica but relatively resistant to another root-knot nematode species (M. incognita), did not share three of the closest markers. These results suggest that at least some genes controlling resistance to M. incognita and M. javanica in ’Brasilia 1252’ reside at distinct loci. The low number of markers suggests a reduced amount of genetic divergence between the parental lines at the region surrounding the target locus. Nevertheless, the low rate of recombination indicated these markers could be useful landmarks for positional cloning of the resistance gene(s). These RAPD markers could also be used to increase the Mj-1 frequency during recurrent selection cycles and in backcrossing programs to minimize ’linkage drag’ in elite lines employed for the development of resistant F₁ hybrids. Received: 22 June 1999 / Accepted: 6 July 1999     

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.     

Effect of root-rot fungus (Macrophomina phaseolina) on the life cycle of root-knot nematode (Meloidogyne javanica) Race-2 on balsam

The penetration of second stage juveniles of Meloidogyne javanica started within 12 hours after inoculation and the rate of penetration gradually increased with the passage of time up to the fifth day in the plants inoculated with root-knot nematode alone and up to the sixth day when plants were infected with root-knot nematode and root-rot fungus. Mostly, the penetration of second stage juveniles of Meloidogyne javanica took place in the meristematic region but in some cases the juveniles also penetrated into the root tips and oriented themselves near the stellar region almost parallel to the longitudinal axis of the roots. The life cycle of Meloidogyne javanica on balsam was completed within 25 days, whereas the duration of the life cycle and fecundity of females was adversely affected in the presence of fungus (Macrophomina phaseolina) and it took about 33 days to complete the life cycle, i.e. the presence of Macrophomina phaseolina delayed the life cycle of the root-knot nematode (Meloidogyne javanica) by eight days.     

Physicochemical and biological properties of the coffee (Coffea arabica) rhizosphere suppress the root-knot nematode Meloidogyne exigua

ABSTRACT

We investigated the properties of rhizospheric soils infested with root-knot nematode (RKN) Meloidogyne exigua in 17 coffee (Coffea arabica) farms from the Southern region of Minas Gerais, Brazil. Physicochemical (pH, clay and organic matter) and biological properties (RKN parasites and microbiota volatile toxicity on M. exigua) were correlated with the number of second-stage juveniles (J₂) and the egg hatching of M. exigua extracted from those rhizospheres. In the five most suppressive farms, the number of J₂ was less than 50/100?g of soil and the egg hatching was significantly low. The bacterium Pasteuria penetrans was found in four of the most suppressive farms with an average of 30% of J₂ infected with endospores. By using in vitro experiments the microbiota volatiles emitted from the most suppressive soils killed more than 83% of the J₂. Additionally, volatiles produced by Fusarium oxysporum, Cladosporium sp. and Syncephalastrum sp. isolated from M. exigua eggs, significantly killed the J₂. Identification of nematicidal compounds from the soils by GC-MS supported the strong involvement of the microbiota volatile toward RKN suppressiveness. Clay percentage and pH were similar in farms with the most suppressive soils (42.5% and 6.6%, respectively). Finally, the most suppressive soils came from farms with the highest coffee bean yields. Collectively, these results suggest the strong involvement of parasitic microorganisms, clay percentage and the pH suppressing RKN in soils from the major coffee production region in Brazil, and that volatiles emitted from total microbiota and exclusively from egg-isolated fungi are toxic to M. exigua.     

丛枝菌根真菌对不同番茄品种抗根结线虫病的影响

【背景】根结线虫病害严重制约我国设施蔬菜的生产。丛枝菌根真菌(Arbuscular Mycorrhizal Fungi,AMF)作为土壤中最重要的有益真菌之一,可以促进植物生长,提高植物抗病性,减轻土传真菌和线虫病害的发生。在蔬菜保护地栽培中,AMF对于植物线虫病防治作用的研究受到了广泛关注。【目的】针对番茄生产中危害最严重的南方根结线虫(Meliodogyne incognita)病害问题,研究AMF和番茄品种不同组合的抗线虫效应,以期为菌根真菌作为生物防治剂和生物菌肥应用于实际生产提供技术基础。【方法】在灭菌土壤中,人工接种根结线虫,比较不同菌种Rhizophagus intraradices(Ri)、Acaulosporamellea(Am)及菌种组合Rhizophagusintraradices+Acaulosporamellea(Ri+Am)在不同番茄品种(感病品种蒙特卡罗和抗线虫品种仙客1号)上对南方根结线虫侵染和繁殖的影响,研究AMF对根结线虫的拮抗效应。另外,采用南方根结线虫连作发病的土壤,在感病品种蒙特卡洛上接种AMF混合菌种Ri+Am,番茄苗移栽入连作土壤中,测定各生长指标和调查根结和卵块数量,评价接种AMF处理对根结线虫病的防治效果。【结果】在灭菌土壤中,普通番茄品种蒙特卡罗的菌根效应显著优于抗线虫番茄品种仙客1号,表现为前者单位根重的根结和卵块的数量均比对照显著降低,而后者仅降低了卵块数量;蒙特卡罗上接种Ri+Am混合菌种的效果优于接种单一菌种Am和Ri;而仙客1号上接种Ri的效果更好。接种线虫也显著影响了AMF的侵染,而且对抗性品种仙客1号的影响更为明显。但除了接种Am的处理,大多数处理收获时菌根侵染率仍维持较高的水平(70%以上)。在连作土壤中,感病品种蒙特卡罗接种混合菌种Ri+Am具有较好的抗/耐线虫效应,主要表现为促进植株生长,显著降低根结和卵块数量,但菌根侵染率较灭菌土壤低,约为40%。【结论】综合以上结果,表明菌根化苗能够在一定程度上减轻根结线虫病的危害。土壤灭菌条件下,在感病和抗线虫番茄品种上接种AMF能够减轻线虫的侵染和繁殖,而且在感病品种上的防治效果更加显著。在连作土壤中,在番茄感病品种上接种AMF也表现较好的抗线虫效果。     

Histological response of resistant tomato cultivars to infection of virulent Tunisian root-knot nematode (Meloidogyne incognita) populations

The response of a susceptible tomato cultivar (Solanum lycopersicum cv. Rio Grande) to infection by three populations of root-knot nematode (Meloidogyne incognita) was compared histologically with that of Lycopersicon esculentum cv. Monita, L. esculentum cv. VFN8 and Solanum lycopersicum cv. Nemador possessing the Mi-1 resistance gene and accession PI126443 of L. peruvianum possessing the Mi-3 gene. The resistant cultivars showed susceptibility to the Tunisian Meloidogyne populations. Feeding sites were characterised by the development of giant cells that contained granular cytoplasm and several hypertrophied nuclei. The cytoplasm of giant cells was aggregated along their thickened cell walls and consequently the vascular tissues within galls appeared disrupted and disorganised. Feeding site formed on resistant L. esculentum lines and susceptible cultivar Rio Grande are similar according to cell and nucleus number, and the nurse superficies. Resistant accession L. peruvianum PI126443, known to possess heat-stable nematode resistance, also showed susceptible reaction to Tunisian Meloidogyne incognita populations; however, nematode development was reduced in comparison with susceptible plants and less developed feeding cells were observed.