Root-knot Nematode Reproduction Research Articles

Use of Bacteria Isolated from Berry Rhizospheres as Biocontrol Agents for Charcoal Rot and Root-Knot Nematode Strawberry Diseases

Strawberry is a high-value crop in Spain, where fruits for fresh consumption are produced off-season and exported to central and northern European countries. Soil-borne pathogens (SBP), such as Macrophomina phaseolina and Meloidogyne hapla, are widely spread in strawberry crops in Spain. The prevalence of these pathogens is a significant barrier to producing strawberries of premium quality and at profitable yields. The current ban on fumigant pesticides drives the search for alternative SBP control methods that can simultaneously control both SBP. Twenty-nine bacterial strains were isolated and identified from strawberry and blueberry rhizospheres and screened for plant growth promotion activities as well as for biocontrol potential on M. phaseolina and M. hapla. Two of these bacterial strains (Bacillus velezensis FC37 and Pseudomonas aeruginosa AC17), together with Brevibacterium frigoritolerans Hvs8 coming from IFAPA’s bacterial collection, were selected and evaluated in planta for their biocontrol potential on strawberry SBP diseases caused by M. phaseolina and M. hapla. The three tested bacterial strains reduced charcoal rot disease severity, crown incidence and severity, and petiole colonization by M. phaseolina. Root-knot nematode (RKN) symptoms were reduced by P. aeruginosa AC17 and B. velezensis FC37, but RKN reproduction was only reduced in plants inoculated with P. aeruginosa AC17. Pseudomonas aeruginosa AC17 showed the greatest potential as a biocontrol agent candidate to be included in integrated disease management programs to control the two most prevalent soil-borne pathogens of strawberry in Spain.

Effect of Soil Temperature on Reproduction of Root-knot Nematodes in Flue-cured Tobacco with Homozygous Rk1 and/or Rk2 Resistance Genes.

Most commercial flue-cured tobacco cultivars contain the Rk1 resistance gene, which provides resistance to races 1 and 3 of Meloidogyne incognita and race 1 of M. arenaria. A number of cultivars now possess a second root-knot resistance gene, Rk2. High soil temperatures have been associated with a breakdown of root-knot resistance genes in a number of crops. Three greenhouse trials were performed from 2014 to 2015 investigate the effect of high soil temperature on the efficacy of Rk1 and/or Rk2 genes in reducing parasitism by a population of M. incognita race 3. Trials were arranged in randomized complete block design in open-top growth chambers set at 25°, 30°, and 35°C. Plants were inoculated with 3,000 eggs and data were collected 35 days post-inoculation. Galling, numbers of egg masses and eggs, and reproductive index were compared across cultivar entries. Nematode reproduction was reduced at 25°C and 30°C on entries possessing Rk1 and Rk1Rk2 compared to the susceptible entry and the entry possessing only Rk2. However, there were often no significant differences in reproduction at 35°C between entries with Rk1 and/or Rk2 compared to the susceptible control, indicating an increase of root-knot nematode parasitism on resistant entries at higher temperatures. Although seasonal differences in nematode reproduction were observed among experiments, relative differences among tobacco genotypes remained generally consistent.

Manejo de nematoides-de-galha em quiabeiro por meio de enxertia em vinagreira-roxa e vinagreira-flor-de-veludo

Abstract The objective of this work was to evaluate the performance of okra grafted onto Hibiscus spp. in the presence and absence of three root knot nematode species. The experimental design was completely randomized in a 4x4 factorial arrangement with ten replicates. The first factor consisted of the following four rootstocks: kenaf (Hibiscus cannabinus), false roselle (Hibiscus acetosella), self-grafted, and non-grafted. The second factor was the inoculation of 5,000 eggs and second-stage juveniles of Meloidogyne incognita, Meloidogyne javanica, and Meloidogyne enterolobii in okra plants, plus an uninoculated control. Vegetative development, agronomic performance, and nematode reproduction were evaluated. The grafting of okra onto Hibiscus spp. in the presence of root-knot nematodes provided a greater plant height, scion length, fresh shoot mass, number of fruits, and yield, when compared with self-grafted and non-grafted plants. The averages of the root-knot nematode reproduction factor were low in the plants grafted onto Hibiscus spp., indicating that grafting in the presence of root-knot nematodes is capable of maintaining okra vegetative development and yield.

Susceptibility and host potential of six cucurbit crops to Meloidogyne enterolobii, M. floridensis, M. hapla, M. incognita and M. javanica

Summary Cucurbits are economically important crops and very susceptible to root-knot nematodes (Meloidogyne spp.; RKN) in Florida. A series of glasshouse and field trials were conducted to evaluate the susceptibility and host potential of different cucurbit crops to different RKN species. We tested the sensitivity of six cucurbit crops (squash, cucumber, cantaloupe, watermelon, smooth and angled luffa) that are commonly grown in Florida to some of the major RKN species, Meloidogyne enterolobii, M. floridensis, M. hapla, M. incognita and M. javanica under glasshouse conditions. In addition, cucumber, squash and zucchini were also tested in two field trials. Meloidogyne incognita was more damaging to all six tested cucurbit crops than M. javanica and M. floridensis in terms of gall index, eggs (root system)−1, eggs (g root)−1 and reproduction factor. In another experiment, the same cucurbit crops suffered greater damage and allowed higher reproduction of M. enterolobii as compared to M. javanica. Meloidogyne hapla caused little damage to all six cucurbit crops and had low reproduction rates, with highest root gall ratings and reproduction for cucumber and cantaloupe, and lowest for watermelon and squash. Meloidogyne enterolobii, M. floridensis, M. incognita and M. javanica caused higher root gall ratings on cucumber and watermelon than on squash, cantaloupe and luffa. This was also noted in the field trials, where cucumber had consistently higher gall indices than squash and zucchini. Root-knot nematode reproduction rates were the highest on squash and cucumber, especially with M. incognita and M. enterolobii. While all cucurbits were good hosts for all tested RKN species, significant differences were noted among cucurbit crops and RKN species.

Interaction Studies Between Meloidogyne Javanica and Fusarium Oxysporum f. Sp. lycopersici (Fol) Race 3 on Different Isolines of Tomato Cv. Tasti Lee.

The Mi gene in tomato confers resistance to Meloidogyne javanica, M. incognita, and M. arenaria, the most common tropical root-knot nematode (RKN) species found in Florida. Fusarium wilt (Fol) is another major problem in Florida tomatoes which may interact with RKN and cause more plant damage. To study the interactions between RKN, Fusarium, and Mi in tomato, two greenhouse experiments were conducted. Both experiments used different isolines (with and without I-3 and Mi genes) of the tomato cultivar Tasti Lee®. In the first experiment, all four isolines were subjected to two levels of RKN (~10,000 eggs/pot and no eggs) and two levels of Fol (1000 cc soil with 1,000 cfu/g at planting and no Fol), both applied at planting. In the second experiment, the two isolines without I-3 were exposed to the same two levels of RKN as described above and three levels of Fol (50 ml Fol with 1×106 cfu/m at planting, at 10 DAT, and no Fol). Fol reduced root-knot infection and reproduction when both Fol and RKN were inoculated at planting but not when Fol was inoculated 10 days later. Plant damage from Fol was exacerbated in the presence of RKN, especially when both pathogens were present at planting. Isolines with I-3 grew better in Fol-inoculated soil but had no effect when Fol and RKN were both present. Isolines with Mi gene reduced RKN infection and reproduction but did not affect plant damage caused by Fol. In summary, while RKN reproduction was reduced in the presence of Fol, the overall plant damage was more severe when both pathogens were present.

Evaluation of nematicidal potential of neem sawdust against Meloidogyne arenaria on eggplant

The present study was conducted to evaluate the impact of amending soil with decomposed neem (Azadirachta indica) sawdust at different concentrations (0-100%) against different inoculum levels (0-4000) of root-knot nematode (Meloidogyne arenaria) infecting the eggplants. Various physico-chemical properties of the soil increase as the concentration of decomposed neem sawdust (NSD) in the field soil increases. Nevertheless, the nitrogen content of the soil decreased with a progressive fluctuation in NSD. Lower levels (10-30%) of NSD, with and without different inoculum levels, improve the plant growth and photosynthetic pigment content significantly compared to controls (plants with uninoculated soil) as well as inoculated plants. The maximum improvement in the growth and photosynthetic pigments was recorded at 30% NSD soil amendment and this was continuously effective against all the nematode inoculum levels. At higher levels of NSD (40-100%), all the studied growth and photosynthetic parameters were decreased gradually to control and a similar reductional trend was also observed on nematode inoculated eggplants. On root-knot nematode reproduction, NSD at all levels progressively suppressed the number of egg masses but enhanced the number of galls only up to 30%. Galling was, however, totally absent in 70% and onward dust treatments of eggplants. Conclusively, NSD suppressed plant growth and photosynthetic pigments along with nematode buildup beyond 40% amendments. Thus, lower NSD levels (up to 30% amendments) will be recommended as growth and photosynthetic pigments supplement to eggplants, which also have nematicidal potential against egg masses of nematodes.

Reproductive Toxicity of Furfural Acetone in Meloidogyne incognita and Caenorhabditis elegans.

Furfural acetone (FAc) is a promising alternative to currently available nematicides, and it exhibits equivalent control efficiency on root-knot nematodes with avermectin in fields. However, its effect on the reproduction of root-knot nematode is poorly understood. In this study, the natural metabolite FAc was found to exhibit reproductive toxicity on Meloidogyne incognita and Caenorhabditis elegans. The number of germ cells of C. elegans was observed to decrease after exposure to FAc, with a reduction of 59.9% at a dose of 200 mg/L. FAc in various concentrations induced the germ-cell apoptosis of C. elegans, with an increase over six-fold in the number of apoptotic germ cells at 200 mg/L. These findings suggested that FAc decreased the brood size of nematode by inducing germ-cell apoptosis. Moreover, FAc-induced germ-cell apoptosis was suppressed by the mutation of gene hus-1, clk-2, cep-1, egl-1, ced-3, ced-4, or ced-9. The expression of genes spo-11, cep-1, and egl-1 in C. elegans was increased significantly after FAc treatment. Taken together, these results indicate that nematode exposure to FAc might inflict DNA damage through protein SPO-11, activate CEP-1 and EGL-1, and induce the core apoptosis pathway to cause germ-cell apoptosis, resulting in decreased brood size of C. elegans.

Elicitation of resistance through the exploration of acibenzolar-S-methyl (ASM) against Meloidogyne incognita in tomato under salt stress condition

Meloidogyne incognita is one of the prime restricting factors of yield in crops. Approaches to diminish the populations are consistently raised, and the application of elicitors as resistance inducers is an option for managing the disease. Thus, this study was conducted to examine the potential of acibenzolar-S-methyl (ASM), a chemical activator, as a soil drench to induce resistance against M. incognita infestation with and without salt stress. Results demonstrated that alone and under salt stress, ASM was able to reduce root-knot nematode population in tomato. The applied treatments significantly reduced the root-knot nematode reproduction, increased growth and phenolic compounds in the plants. Treatment of ASM (0.254 mM) with NaCl (100 mM), significantly reduced the root-knot index by 58.0% compared to untreated control. The same combination significantly enhanced the phenolic compounds and dry matter up to 60.6% and 59.0%, respectively, compared to inoculated control. However, the application of the highest concentration of ASM (1.019 mM) alone was the most potent in reducing the eggmasses and root-knot index by 74.4% and 68.0% respectively compared to inoculated control. Additionally, the lowest increase (23.0%) of phenol was observed in ASM (0.509 mM). NaCl alone also reduced the root-knot index by 32.0% and increased phenol accumulation by 47.5%. Moreover, lower concentration of ASM (0.254 mM) in combination with salt stress (NaCl 100 mM) showed significantly higher efficacy. The study revealed that application of ASM through stress modulation effect can activate the inherent M. incognita resistance in tomato, which could contribute substantially in sustainable management of nematode infestation.

Analysis of Cotton Chromosome 11 and 14 Root-Knot Nematode Resistance Quantitative Trait Loci Effects on Root-Knot Nematode Postinfection Development, Egg Mass Formation, and Fecundity.

Cotton (Gossypium hirsutum) resistance to root-knot nematode (RKN) (Meloidogyne incognita) is controlled by quantitative trait loci (QTLs) on chromosomes 11 (CHR11) and 14 (CHR14). The individual contributions of these QTLs to resistance are not completely understood. We developed near isogenic lines susceptible at both loci (null), having CHR11 or CHR14 alone, and having both QTLs (CHR11/CHR14). RKN reproduction, postinfection development, egg mass formation, and adult female fecundity were evaluated. Total RKN reproduction was reduced more in CHR14 versus CHR11 but not as greatly as in CHR11/CHR14. Second-stage juvenile (J2) development to the J3 and J4 (J3+J4) life stages was delayed in CHR11, whereas the J2 transition to J3+J4 in CHR14 followed a similar track as in null plants. Development of J3+J4 nematodes to adult females was inhibited in CHR14 at 21 days after inoculation (DAI). Adult female numbers were decreased in CHR11 and CHR14 at 21 and 28 DAI, with CHR11/CHR14 showing an even greater reduction by 28 DAI. The number of egg masses per gram of root at 21, 28, and 35 DAI formed on CHR11 and CHR14 followed a similar track as numbers of adult females. RKN adult female fecundity (eggs/egg mass) was reduced for CHR11 and CHR14 compared with the null at 21 DAI; however, CHR11 eggs/egg mass was only slightly reduced versus the null by 28 DAI. In contrast, CHR14 eggs/egg mass was like CHR11/CHR14, showing a 4-fold decrease compared with CHR11 and the null.

The plant WEE1 kinase is involved in checkpoint control activation in nematode-induced galls.

Galls induced by plant-parasitic nematodes involve a hyperactivation of the plant mitotic and endocycle machinery for their profit. Dedifferentiation of host root cells includes drastic cellular and molecular readjustments. In such a background, potential DNA damage in the genome of gall cells is evident. We investigated whether DNA damage checkpoint activation followed by DNA repair occurred, or was eventually circumvented, in nematode-induced galls. Galls display transcriptional activation of the DNA damage checkpoint kinase WEE1, correlated with its protein localization in the nuclei. The promoter of the stress marker gene SMR7 was evaluated under the WEE1-knockout background. Drugs inducing DNA damage and a marker for DNA repair, PARP1, were used to understand the mechanisms for coping with DNA damage in galls. Our functional study revealed that gall cells lacking WEE1 conceivably entered mitosis prematurely, disturbing the cell cycle despite the loss of genome integrity. The disrupted nuclei phenotype in giant cells hinted at the accumulation of mitotic defects. In addition, WEE1-knockout in Arabidopsis and downregulation in tomato repressed infection and reproduction of root-knot nematodes. Together with data on DNA-damaging drugs, we suggest a conserved function for WEE1 in controlling G1/S cell cycle arrest in response to a replication defect in galls.

Saccharum spontaneum, a Novel Source of Resistance to Root-Lesion and Root-Knot Nematodes in Sugarcane.

Root-lesion nematode (Pratylenchus zeae) and root-knot nematode (Meloidogyne javanica) are two important pathogens of sugarcane (Saccharum hybrid). No commercial cultivars are resistant to these nematodes in Australia. Twenty accession lines of S. spontaneum, a wild relative of sugarcane, were tested against these two nematode species. S. spontaneum lines were tested twice for resistance to root-lesion nematode and three times for root-knot nematode. Reproduction (final population/starting population) of root-lesion nematodes was significantly lower in 17 of the 20 S. spontaneum accession lines tested in two experiments compared with two commercial cultivars. Four S. spontaneum lines supported a significantly lower number of root-lesion nematodes per gram of root than that of two commercial sugarcane cultivars. Reproduction of root-knot nematodes was significantly lower in 16 S. spontaneum lines compared with two commercial cultivars. Fourteen of the S. spontaneum lines tested supported significantly fewer eggs per gram of root compared with two commercial cultivars. This study showed that S. spontaneum lines possessed resistance for root-lesion and root-knot nematodes. Targeted crossing with commercial hybrid parental lines should be conducted to introduce nematode resistance into sugarcane cultivars for the Australian sugar industry.

Survey of root knot nematodes and RMi resistance to Meloidogyne incognita in soybean from Khyber Pakhtunkhwa, Pakistan

The root knot nematode (RKN), Meloidogyne spp. is one of the most significant pests limiting the agricultural productivity. The RKN constitute the most widely distributed group among the plant parasitic nematodes. This study was carried out to find the pathogenicity of Meloidogyne incognita in soybean. Occurrence and prevalence of Meloidogyne species in soybean fields along with categorization of soybean varieties on the basis of resistance to M. incognita was also studied. An extensive survey for RKN was carried out from Khyber Pakhtunkhwa (KPK) province of Pakistan. The most prevalent specie in all studied hot spots was M. incognita, followed by M. javanica that was observed in Akbar Pura, Bari Kot, and Dargai. In this study, fifteen soybean varieties were generously provided by agricultural field’s farmers and National Agriculture Research Centre of Pakistan. These selected varieties were assessed against M. incognita in experimental area of National Nematological Research Center, University of Karachi in three separate trials from 2014 to 2016. Internationally known susceptible (Bossier and Lee) and resistant (Gregg and Forrest) soybean varieties were checked as positive controls. The reproduction factor (RF) and damage index (DI) were employed to sort out the varieties as resistant or susceptible. Statistically significant differences (P < 0.01) were noticed amongst the studied varieties for RKN reproduction factors such as egg mass index (EMI), gall index (GI) and Juveniles/250 g soil. Moreover, thirty SSR markers were used for the identification of RMi gene, amongst them only three diagnostic markers exhibited the presence of RMi gene in resistant varieties. The resistant genotypes are potential materials against M. incognita. In the present investigation, molecular results confirmed locus of RMi gene in resistant genotypes and their functional presence in nematode management programs for choosing resistant varieties in the field. For the confirmation of resistance in soybean against RKN different biochemical indicators, which play active role in resistance mechanism, were also studied. Resistant varieties exhibited maximum amount of phenol, salicylic acid, chlorogenic acid and ascorbic acid as compared to susceptible plants.

Effects of inducers of systemic acquired resistance on reproduction of root knot nematodes in tomato

Effects of inducers of systemic acquired resistance on reproduction of root knot nematodes in tomato

English

Root-knot nematodes cause substantial economic yield loss in tobacco production and many other crops in the world. Their control has been achieved for decades by use of chemical nematicides. However, concern for the environment has led to the banning and phasing out of some effective chemical nematicides. The use of crop rotation is one of the environmentally friendly and sustainable management strategies for managing root-knot nematodes, insect pests and pathogens. The strategy is widely used by resource poor farmers in developing countries. In this study, greenhouse experiments were conducted with the objective of evaluating four leguminous crops (groundnut, sunhemp, common bean and cowpea cultivars) for their efficacy in the management of the root-knot nematode (Meloidogyne javanica). Experimental plants were grown in 15 cm diameter pots and artificially inoculated with nematode eggs. Four different initial inoculums levels of 0, 500, 1,000 and 1,500 nematodes eggs per plant were used. After inoculation the plants were maintained in the greenhouse for 54 days. Thereafter, the nematode reproductive factor and the number of eggs were evaluated. Significant differences (P&lt;0.05) in nematode population built up were observed in plots with the different legumes. Generally, all the groundnut cultivars were effective in reducing populations while common bean was a susceptible host and supported high nematode populations. The results from this study demonstrate that some leguminous crops affect this pest&rsquo;s capacity to develop within their roots. The test legumes may contain compounds that either kill or deter root-knot nematode reproduction. Key words: Antagonist plant, Meloidogyne javanica, crop rotation, groundnut, sunnhemp, common bean, cowpea. &nbsp

Resistance screening of lentil cultivars against the root-knot nematode Meloidogyne incognita

Summary The root-knot nematode Meloidogyne incognita is a major soil parasite of lentil crops. Increasing restrictions of chemical nematicides have triggered a growing attention and interest in alternate root-knot nematode management. The present study was conducted to examine the level of resistance and/or susceptibility of five lentil cultivars (PL-456, KLS-218, Desi, DPL-62, Malika), grown in pots, against the root-knot nematode M. incognita. Root-knot nematode reproduction and host damage were assessed by recording the nematode infestation levels and reduction percentage of plant growth parameters. Nematode response and plant growth differentiated amongst the lentil cultivars. None of the cultivars was found immune or highly resistant. The cultivar Malika was found moderately resistant as it showed the lowest number of galls and egg masses/root as well as the lowest reduction of plant fresh weight (10.4%) and dry weight (6.9%). On the other hand, the cultivar Desi manifested the highest susceptibility exhibiting the highest number of galls and egg masses. There was a significantly negative correlation between the number of galls and plant growth parameters (plant fresh and dry weight and plant height).

Meloidogyne incognita Fatty Acid- and Retinol- Binding Protein (Mi-FAR-1) Affects Nematode Infection of Plant Roots and the Attachment of Pasteuria penetrans Endospores.

Root-knot nematode (RKN) Meloidogyne incognita is an economically important pest of crops. Pasteuria penetrans, is a nematode hyperparasitic bacterium capable of suppressing the reproduction of RKN and thereby useful for its management. Secreted fatty acid and retinol-binding proteins are unique in nematodes and are engaged in nutrient acquisition, development and reproduction; they are also a component of the nematode cuticle and thought to be involved in the interface between hosts and parasites. Attachment of endospores to the cuticle of second stage juveniles of RKN is the primary step of infection and several factors have been identified to facilitate attachment. In this study, the full length of Mi-far-1 (573 bp) was cloned from M. incognita and characterized. Analysis revealed that the Mi-far-1 was rich in α-helix structure, contained a predicted consensus casein kinase II phosphorylation site and a glycosylation site. Quantitative PCR showed the highest expression in the fourth stage juveniles and in situ hybridization revealed the presence of Mi-far-1 mRNA in the hypodermis below the cuticle. Single copy insertion pattern of Mi-far-1 in M. incognita genome was detected by Southern blotting. Knockdown of Mi-far-1 showed significantly increased attachment of P. penetrans’ endospores on juvenile cuticle surface and also affected host finding, root infection and nematode fecundity.

Rhizobacteria cooperative effect against Meloidogyne javanica in rhizosphere of legume seedlings

Summary Root-knot nematodes are major pests of legume fields in Iran. This research evaluated the effect of Rhizobium leguminosarum bv. phaseoli and Pseudomonas fluorescens CHA0 (stand alone and combination treatment) on galling and reproduction of root-knot nematode, Meloidogyne javanica, in legum (chickpea, bean, lentil, pea) seedling rhizosphere, and the growth properties of the host plants. The legumes seeds were sown in 1kg sterilized sandy loam soil. Inocula were 5 J2/g of soil, in the case of the nematode, while considering the bacteria 1×107 cfu/kg soil. A treatment of nematicide (cadusafos) was performed, as a commonly used nematicide in Iran, at 2g/kg soil. Two months after inoculation, the following parameters were recorded: the number of knots, egg masses and reproduction factor of the nematode, bacterial nodules per root, and growth properties of seedlings in the treatments (control, nematode, nematode+nematicide, and nematode+rhizobacteria). The greatest bacterial effect on the control of the nematode was observed in the rhizosphere of the bean treatments. Inoculation with Rhizobium in the soil decreased the galling on the legumes’ roots, and the combined inoculation with Pseudomonas and Rhizobium resulted in a higher decrease of the galling.

Fine mapping and identification of candidate genes for a QTL affecting Meloidogyne incognita reproduction in Upland cotton.

BackgroundThe southern root-knot nematode (Meloidogyne incognita; RKN) is one of the most important economic pests of Upland cotton (Gossypium hirsutum L.). Host plant resistance, the ability of a plant to suppress nematode reproduction, is the most economical, practical, and environmentally sound method to provide protection against this subterranean pest. The resistant line Auburn 623RNR and a number of elite breeding lines derived from it remain the most important source of root-knot nematode (RKN) resistance. Prior genetic analysis has identified two epistatically interacting RKN resistance QTLs, qMi-C11 and qMi-C14, affecting gall formation and RKN reproduction, respectively.ResultsWe developed a genetic population segregating only for the qMi-C14 locus and evaluated the genetic effects of this QTL on RKN resistance in the absence of the qMi-C11 locus. The qMi-C14 locus had a LOD score of 12 and accounted for 24.5 % of total phenotypic variation for egg production. In addition to not being significantly associated with gall formation, this locus had a lower main effect on RKN reproduction than found in our previous study, which lends further support to evidence of epistasis with qMi-C11 in imparting RKN resistance in the Auburn 623RNR source. The locus qMi-C14 was fine-mapped with the addition of 16 newly developed markers. By using the reference genome sequence of G. raimondii, we identified 20 candidate genes encoding disease resistance protein homologs in the newly defined 2.3 Mb region flanked by two SSR markers. Resequencing of an RKN resistant and susceptible G. hirsutum germplasm revealed non-synonymous mutations in only four of the coding regions of candidate genes, and these four genes are consequently of high interest.ConclusionsOur mapping results validated the effects of the qMi-C14 resistance locus, delimiting the QTL to a smaller region, and identified tightly linked SSR markers to improve the efficiency of marker-assisted selection. The candidate genes identified warrant functional studies that will help in identifying and characterizing the actual qMi-C14 defense gene(s) against root-knot nematodes.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-016-2954-1) contains supplementary material, which is available to authorized users.

Biological services by Streptomyces lavendulae MTCC 706 to control invasion, development and reproduction of root-knot nematode (Meloidogyne incognita) infecting tomato cv Pusa Ruby

The drench application of S. lavendulae MTCC706 @ 2% v/w (SLT) resulted in less than 50% juvenile invasion of M. incognita J2s in tomato (cv. Pusa Ruby), delayed development of J4s, 50.7% reduction in root galling and 42.7% reduction in egg mass production, compared to control. The reproduction factor was 1.2 in SLT, compared to 2.4 in control in 45 days. SLT was compatible with the nematicide carbofuran, as increase in bioefficacy of SLT was observed with 60% reduction in root galling, 61.5% reduction in egg mass production, and a reproduction factor of 1.1 in the combined application with carbofuran @0.5 kg a.i/ha. Replanting of tomato in the pre-treated soil revealed a further reduction in root galling (81.3%), egg mass production (80.5%) and reproduction factor (0.6), indicating establishment of the actinomycete in the soil.

Coupling of MIC-3 overexpression with the chromosomes 11 and 14 root-knot nematode (RKN) (Meloidogyne incognita) resistance QTLs provides insights into the regulation of the RKN resistance response in Upland cotton (Gossypium hirsutum)

Genetic analysis of MIC-3 transgene with RKN resistance QTLs provides insight into the resistance regulatory mechanism and provides a framework for testing additional hypotheses. Resistance to root-knot nematode (RKN) (Meloidogyne incognita) in Upland cotton (Gossypium hirsutum) is mediated by two major quantitative trait loci (QTL) located on chromosomes 11 and 14. The MIC-3 (Meloidogyne Induced Cotton3) protein accumulates specifically within the immature galls of RKN-resistant plants that possess these QTLs. Recently, we showed that MIC-3 overexpression in an RKN-susceptible cotton genotype suppressed RKN egg production but not RKN-induced root galling. In this study, the MIC-3 overexpression construct T-DNA in the single-copy transgenic line '14-7-1' was converted into a codominant molecular marker that allowed the marker assisted selection of F2:3 cotton lines, derived from a cross between 14-7-1 and M-240 RNR, having all possible combinations of the chromosomes 11 and 14 QTLs with and without the MIC-3 overexpression construct. Root-knot nematode reproduction (eggs g(-1) root) and severity of RKN-induced root galling were assessed in these lines. We discovered that the addition of MIC-3 overexpression suppressed RKN reproduction in lines lacking both resistance QTLs and in lines having only the chromosome 14 QTL, suggesting an additive effect of the MIC-3 construct with this QTL. In contrast, MIC-3 overexpression did not improve resistance in lines having the single chromosome 11 QTL or in lines having both resistance QTLs, suggesting an epistatic interaction between the chromosome 11 QTL and the MIC-3 construct. Overexpression of MIC-3 did not affect the severity of RKN-induced root galling regardless of QTL genotype. These data provide new insights into the relative order of action of the chromosomes 11 and 14 QTLs and their potential roles in regulating MIC-3 expression as part of the RKN resistance response.