Evidence for simply inherited dominant resistance to Meloidogyne javanica in carrot

Root-knot nematodes (Meloidogyne spp.) are serious pests of carrot (Daucus carota L.) worldwide. While soil treatment with nematicides is the primary means for managing nematodes in carrot, there is a need to identify and introduce host plant resistance for crop improvement. This study was conducted to determine the inheritance of resistance to root-galling and reproduction by M. javanica (Treub) Chitwood in a selection (BR-1252) of carrot variety Brasilia. F₂, F₃, F₄, and BC₁ progenies from the cross BR-1252×B6274 (a susceptible inbred line) were screened in pot tests for reaction to M. javanica. The observed reactions based on galling and egg production on fibrous roots gave segregation patterns in all tests that were consistent with relatively simply inherited dominant resistance. Field testing in progress indicates that this resistance is very effective against both M. javanica and M. incognita. A single gene model fits the observed data acceptably well in F₃ generations. However, the range of 3% to 51% susceptible plants in segregating F₃ families and 1% to 47% in segregating F₄ families is much wider than the 25% expected with a single-gene model, and linked duplicate factors in the coupling phase could also explain the observed segregation patterns. The variation in percentage susceptibility among these families did not clearly cluster into three expected categories (25% S, 20.25% S, and 0.25% S for a 10-cM linkage distance, or 25% S, 16% S and 1% S for 20 cM), but it did tend to occur over the same range. Thus a 10-cM to 20-cM-linked duplicate factor model cannot be dismissed at this time. Egg production data in the F₂, F₃, and F₄ families provided evidence for slightly lower resistance expression in the heterozygous condition. Thus, while overall expressed in a dominant fashion, the resistance does exhibit some allelic dosage response. Received: 14 June 1999 / Accepted: 7 July 1999     

RAPD and SCAR markers linked to the Ma1 root-knot nematode resistance gene in Myrobalan plum (Prunus cerasifera Ehr.)

 The Myrobalan plum (Prunus cerasifera) is a self-incompatible species in which the clones P.2175, P.1079 and P.2980 are highly resistant to all root-knot nematodes (RKN), Meloidogyne spp. Each clone bears a single major dominant gene, designated Ma1, Ma2 and Ma3 respectively, that controls a high and wide-spectrum resistance. Bulked segregant analysis (BSA) and random amplified polymorphic DNA (RAPD) analysis were both performed to detect markers linked to the Ma1 gene using three segregating progenies from P.2175 (Ma1 ma1) crossed by three host parents (ma1 ma1). Four dominant coupling-phase markers were identified from a total of 660 10-base primers tested. The resulting linkage map spans 14.7 cM and comprises three markers located on the same side of Ma1 and one marker located on the other side. The nearest markers (OPAL19₇₂₀ and OPA16₁₄₀₀) are located at 3.7 and 6.7 cM, respectively, on each side of the gene. Among the three markers that could be successfully converted into sequence characterized amplified region (SCAR) markers, two of them (SCAL19₆₉₀ and SCAN12₆₂₀) were scored as dominant markers whereas the third (SCAO19₇₇₀) failed to produce any polymorphism. SCAL19, and to a lesser extent SCAN12, can be used reliably in the marker-assisted selection of Prunus rootstocks. These markers are adequate to identify the Ma1 RKN resistance gene in intraspecific segregating progenies and will be suitable for the creation of interspecific rootstocks involving Myrobalan plum. Some of the RAPD and SCAR markers for Ma1 were also recovered in clones P.1079 and P.2980, but not in additional host clones, suggesting that Ma1, Ma2 and Ma3 are either allelic or at least closely linked. Received: 22 September 1998 / Accepted: 19 December 1998     

High-resolution genetic mapping of the pepper (Capsicum annuum L.) resistance loci Me3 and Me4 conferring heat-stable resistance to root-knot nematodes (Meloidogyne spp.)

The PM687 line of Capsicum annuum L. has a single dominant gene, Me ₃ , that confers heat-stable resistance to root-knot nematodes (RKN). Me ₃ was mapped using doubled-haploid (DH) lines and F₂ progeny from a cross between the susceptible cultivar ’Yolo Wonder’ (’YW’) and the highly resistant line ’PM687’. Bulked-segregant analysis with DNA pools, from susceptible or resistant DH lines, was performed to identify RAPD and AFLP markers linked to Me ₃ . There was no polymorphism between bulks of ten DH lines using over 800 RADP primers (4,000 amplified fragments analysed). Using 512 AFLP primers (74,000 amplified fragments analysed), and bulked DNA templates from 20 resistant and 20 susceptible plants, we identified eight repulsion-phase and four coupling-phase markers linked to Me _3. Analysed in 103 DH progeny, they defined a 56.1-cM interval containing the target gene. The nearest were located 0.5, 1.0, 1.5 and 3.0 centimorgans (cM) on both sides of the gene. Analysis of the F₂ progeny (162 plants) with the nearest coupling-phase marker confirmed its close position. Another resistance gene to RKN, present in ’PM687’ (Me ₄ ), was shown to be linked to Me ₃ , 10 cM from it. In order to localize Me ₃ and Me ₄ on our reference intraspecific pepper linkage map, two AFLP markers were mapped. The Me ₃ nearest marker was 10.1cM from a RAPD marker named Q04_0.3 and 2.7cM from a RFLP marker named CT135. We investigated map-position orthologies between Me ₃ and two other nematode resistance genes, the tomato Mi-3 and the potato Gpa ₂ genes, which mapped in the telomeric region of the short arm of the tomato and potato chromosome 12 (or XII for potato). Received: 23 March 2000 / Accepted: 2 January 2001     

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 citrus nematode resistance and its linkage with molecular markers

Eleven RAPD markers linked to a gene region conferring resistance to citrus nematodes in an intergen-eric backcross family were identified. Two sequence- characterized amplified region markers linked to a citrus tristeza virus resistance gene and one selected resistance gene candidate marker were evaluated for their association with citrus nematode resistance. A nematode-susceptible citrus hybrid, LB6-2 [Clementine mandarin (Citrus reticulata)×Hamlin orange (C. sinensis)], was crossed with the citrus nematode-resistant hybrid Swingle citrumelo (C. paradisi×Poncirus trifoliata) to produce 62 hybrids that were reproduced by rooted cuttings. The plants were grown in a greenhouse and inoculated with nematodes isolated from infected field trees. The hybrids segregated widely for this trait in a continuous distribution, suggesting possible polygenic control of the resistance. Bulked segregant analysis was used to identify markers associated with resistance by bulking DNA samples from individuals at the phenotypic distribution extremes. Linkage relationships were established by the inheritance of the markers in the entire population. A single major gene region that contributes to nematode resistance was identified. The resistance was inherited in this backcross family from the grandparent Poncirus trifoliata as a single dominant gene. QTL analysis revealed that 53.6% of the phenotypic variance was explained by this major gene region. The existence of other resistance-associated loci was suggested by the continuous phenotypic distribution and the fact that some moderately susceptible hybrids possessed the resistance-linked markers. The markers may be useful in citrus rootstock breeding programs if it can be demonstrated that they are valid in other genetic backgrounds. Received: 4 May 1999 / Accepted: 21 September 1999     

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.     

Development and characterization of a codominant marker linked to root-knot nematode resistance, and its application to peach rootstock breeding

 The presence of a codominant AFLP marker, EAA/MCAT10, correlates with the primary source of resistance to root-knot nematodes (Meloidogyne incognita and M. javanica) in rootstock cultivars of peach [Prunus persica (L.) Batsch]. Two allelic DNA fragments of this AFLP marker were cloned, sequenced and converted to sequence tagged sites (STS). Four nucleotide differences (i.e. one addition and three substitutions) were observed between the two clones. Furthermore, there was a diagnostic Sau3 AI cleavage site (GATC) in the large fragment that was absent from the small fragment (GTTC at this site). The applicability of this STS marker system to peach germplasm improvement was evaluated: genomic DNAs of cross parents (i.e. ‘Lovell’ and ‘Nemared’), four F₁ hybrids (K62-67, K62-68, P101-40 and P101-41) and two F₂ populations (from K62-68 and P101-41), as well as DNA from a test panel of 18 rootstock cultivars or selections, were PCR-amplified with the Mij3F/Mij1R primer pair and then digested with Sau3 AI. The banding patterns showed that the EAA/MCAT10 STS markers can clearly distinguish the three genotypes – homozygous resistant, heterozygous resistant and homozygous susceptible – in the ‘Lovell’בNemared’ cross. In addition, results from the rootstock survey were consistent with each rootstock’s phenotypic response to nematode infection, except for ‘Okinawa’, ‘Flordaguard’ and ‘Yunnan’ where root-knot resistance may have arisen independently. Therefore, the EAA/MCAT10 STS markers will be a useful tool to initiate marker assisted selection studies in peach rootstock breeding for root-knot nematode resistance. Received: 4 January 1999 / Accepted: 4 January 1999     

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.     

Rice root-knot nematode (Meloidogyne graminicola) infestation in rice

Rice (Oryza sativa) is an important staple food crop for majority of human population in the world in general and in Asia in particular. However, among various pests and diseases which constitute important constraints in the successful crop production, plant parasitic nematodes play an important role and account for yield losses to the extent of 90%. The major nematode pests associated with rice are Ditylenchus angustus, Aphelenchoides besseyi, Hirschmanniella spp., Heterodera oryzicola and Meloidogyne graminicola. However, rice root-knot nematode (M. graminicola) happens to be the most important pest and is prevalent in major rice producing countries of the world. In India, the distribution of M. graminicola in rice growing areas of different states has been documented in nematode distribution atlas prepared by All India Coordinated Research Project (Nematodes) and published by Directorate of Information and Publications of Agriculture, Indian Council of Agricultural Research, New Delhi, India during 2010. M. graminicola affected rice plants show stunting and chlorosis due to the characteristic terminal swellings/galls on the roots which ultimately result in severe reduction in growth and yield. Number of eco-friendly management technologies against M. graminicola have been developed and demonstrated, including the use of bioagents for minimising the losses due to rice root-knot nematode. This review is focused on collating information to understand the current scenario of rice root-knot nematodes with greater emphasis on its ecological requirements, damage symptoms, biology, morphology, host range and management strategies.     

Effects of Pseudomonas fluorescens strain UTPF5 on the mobility,mortality and hatching of root-knot nematode Meloidogyne javanica

The root-knot nematode Meloidogyne spp. includes important plant pathogens worldwide. This study has considered nematode Meloidogyne javanica second stage larvae activity in the extracts of Pseudomonas fluorescens strains UTPF5 and cytotoxic effect of the strain on the nematode. The movement of second stage larvae of nematodes in water agar medium at four concentrations of bacterial extracts and second stage larvae mortality rate of hatching nematode and bacterial strains in vitro were affected. Different concentrates of the strain UTPF5 effect nematode larvae movement and disposal of the same. Bacterial extraction kills almost 100% of the larvae hatching after 24?h and a complete ban on egg hatch of biocontrol nematodes and nematode indicated that root-knot nematode larvae movement on the right attract the bacteria P. fluorescens to extract in the first place.     

Spectrum of the Ma genes for resistance to Meloidogyne spp. in Myrobalan plum

The Myrobalan plum, Prunus cerasifera, bears a complete-spectrum resistance to the root-knot nematodes (RKN) Meloidogyne spp. in comparison to the main resistance sources in Amygdalus rootstocks that have more restricted spectra, as evidenced by a differential resistance test based on the predominant species M. arenaria, M. incognita and M. javanica and the population M. sp. Floride. Resistance to M. arenaria (A) in Myrobalan plum is controlled by the Ma major resistance genes that are completely dominant and confer a non-host behaviour that totally prevents the multiplication of the nematode. The inheritance of resistance of this self-incompatible species to M. incognita (I), M. javanica (J) and the population M. sp. Floride (F), considered as belonging to a new RKN species, was studied using G₁ hybrids from a diallel cross based on five parents, the two resistant P.2175 (Ma1 gene; heterozygous) and P.1079 (Ma2 gene; homozygous) and three host parents, P.2032, P.2646 and P.16.5 (recessive for both genes), completed with the G₂ backcrosses P.16.5×(P.2646×P.1079), P.2646 ×(P.16.5×P.1079) and P.2175×(P.2646×P.1079). G₁ and G₂ clones obtained from softwood cuttings sampled from trees in the field experimental design, rooted in the nursery, and inoculated in containers (six replicates per clone) under greenhouse conditions, were simultaneously evaluated for their host suitability to two to four of the RKN species, based on a 0–5 gall index (GI) rating under a high and durable inoculum pressure of the nematode, and then classified into resistant (R; GI?0.2) or host (H; GI?1.3) classes. The resistance classification of each individual clone, evaluated to two (A/J: 319 clones), three (A/J/I: 249 clones) and four (A/J/I/F: 161 clones) RKN species, from segregating and non-segregating crosses involving either Ma1 or Ma2 or both or none, was identical whatever the species. The independence of the R/H classification from the tested RKN indicates that the Ma1 and Ma2 genes control resistance to all of them, and it is assumed that these genes also control resistance to other minor RKN species. The relationship of the Ma genes with the putative genes involved in Amygdalus sources is discussed with the objective of introducing them into new interspecific rootstocks expressing a complete-spectrum and high-level resistance.     

A Seinhorst Model Determined the Host-Parasite Relationships of Meloidogyne javanica Infecting Fenugreek cv. UM202

Root-knot nematodes (RKNs) have been shown to be challenging and persistent pests of economic crops worldwide. Among RKNs, Meloidogyne javanica is particularly important, as it rapidly spreads and has a diverse host range. Measuring its damaging threshold level will help us to develop management strategies for adequate plant protection against nematodes. In our study, we observed the relationship between a linear series of 12 initial population densities (P_i) of M. javanica, i.e., 0, 0.125, 0.25, 0.5, 1, 2, 4, 8, 16, 32, 64, and 128 second-staged juveniles (J2s) g^-1 soil, and fenugreek cv. UM202 growth parameters were investigated using a Seinhorst model. A Seinhorst model was fitted to shoot length and dry weight data for fenugreek plants. A positive correlation was found between J2s inoculum levels and percent reductions in growth parameters. The 1.3 J2s of M. javanica g^-1 soil were found to damage threshold levels with respect to shoot length and shoot dry weight of fenugreek plants. The minimum relative values (m) for shoot length and shoot dry weight were 0.15 and 0.17, respectively, at P_i =128 J2s g^-1 soil. The maximum nematode reproduction rate (P_f /P_i) was 31.6 at an initial population density (P_i) of 2 J2s g^-1 soil.     

Adventitious shoot formation induced by the root-knot nematode Meloidogyne hapla

 Observations were made on the infection process of the temperate sedentary root-knot nematode, Meloidogyne hapla, into roots of Arabidopsis thaliana (L.) Heynh cv. Landsberg erecta in monoxenic culture . After invasion, the infective second-stage juveniles follow a similar migratory path as has been observed in other Meloidogyne species, moving toward and turning within the root tip, to invade the vascular system and initiate the permanent feeding sites. About a week after invasion, there was extensive production of roots at the feeding site and, about 1 week later, the formation of adventitious shoots was observed at about 4.5% of all galls formed. In comparison, very little root production and no shoot formation was found on feeding sites of M. incognita. Received: 22 May 1998 / Revision received: 18 April 1999 / Accepted: 3 June 1999     

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.     

Identification of peanut (Arachis hypogaea L.) RAPD markers diagnostic of root-knot nematode (Meloidogyne arenaria (Neal) Chitwood) resistance

DNA markers linked to a root-knot nematode resistance gene derived from wild peanut species have been identified. The wild diploid peanut accessions K9484 (Arachis batizocoi Krapov. & W. C. Gregory), GKP10017, (A. cardenasii Krapov & W. C. Gregory), and GKP10602 (A. diogoi Hoehne) possess genes for ressitance to Meloidogyne arenaria. These three accessions and A. hypogaea cv. Florunner were crossed to generate the hybrid resistant breeding line TxAg-7. This line was used as donor parent to develop a BC₄F₂ population segregating for resistance. Three RAPD markers associated with nematode resistance were identified in this population by bulked segregant analysis. Linkage was confirmed by screening 21 segregatingh BC₄F₂ and 63 BC₅F₂ single plants. Recombination between marker RKN410 and resistance, and between marker RKN440 and resistance, was estimated to be 5.4±1.9% and 5.8±2.1%, respectively, on a per-generation basis. These two markers identified a resistance gene derived from either A. cardenasii or A. diogoi, and were closely linked to each other. Recombination between a third marker, RKN229, inherited from A. cardenasii or A. diogoi, and resistance was 9.0±3.2% per generation. Markers RKN410 and RKN229 appeared to be linked genetically and flank the same resistance gene. All markers were confirmed by hybridization of cloned or gel-purified marker DNA to blots of PCR-amplified DNA. Pooled data on the segregation of BC₅F₂ plants was consistent with the presence of one resistance gene in the advanced breeding lines. Different distributions of resistance in the BC₅F₂ progeny and TxAG-7 suggest the presence of additional resistance genes in TxAG-7.     

Suppression of fecundity of the root-knot nematode, Meloidogyne javanica, in monoxenic cultures of Arabidopsis thaliana treated with an alkaline extract of Ascophyllum nodosum

Treatment of Arabidopsis thaliana plants with a commercially-available, alkaline extract of the marine brown alga, Ascophyllum nodosum, resulted in a significant decrease in the number of females of the root-knot nematode, Meloidogyne javanica, which developed in the roots compared to those of plants grown in a water control medium. Significant reductions in egg recovery were also achieved from plants treated with the seaweed extract. Similar effects were produced when betaine components of the seaweed extract (γ-aminobutyric acid betaine, δ-aminovaleric acid betaine and glycinebetaine) were used in quantities equivalent to those applied in the seaweed extract treatment. As the experiments were conducted under monoxenic conditions, it can be concluded that the results obtained with the application of either the seaweed extract or betaines are indicative of their effects on the plants and are not dependent on microorganisms associated with the rhizosphere. This revised version was published online in June 2006 with corrections to the Cover Date.     

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.     

RAPD markers linked to a gene for resistance to pine needle gall midge in Japanese black pine (Pinus thunbergii)

Linkage of RAPD markers to a single dominant gene for resistance to pine needle gall midge was investigated in Japanese black pine (Pinus thunbergii). Three primers that generated linked markers were found after 1160 primers were screened by bulked segregant analysis. The distances between the resistance gene, R, and the marker genes OPC06580, OPD01700, and OPAX192100 were 5.1 cM, 6.7 cM and 13.6 cM, respectively. OPC06580 was in coupling phase to R, whereas OPD01700 and OPAX192100 were in repulsion phase to R. A linkage map for a resistant tree was constructed using 96 macrogametophytes. In linkage analysis, 98 out of 127 polymorphic markers were assigned to 17 linkage groups and six linked pairs. The total length of this map was 1469.8 cM, with an average marker density of 15.6 cM. The genome length was estimated to be 2138.3 cM, and the derived linkage map covered 67.5% of the genome. Although the linked markers OPC06580, OPAX192100, and OPD01700, belonged to the same linkage group, no precise positions were found for OPC06580 or OPD01700. Received: 15 May 1999 / Accepted: 29 July 1999