Root-knot Nematode Populations Research Articles

The response of rice varieties to Meloidogyne graminicola from the Mekong Delta, Vietnam

Summary The rice root-knot nematode, Meloidogyne graminicola, is a serious pathogen of rice production worldwide. In Vietnam, scientific information on the rice root-knot nematode is limited. In this circumstance, our study aimed to investigate the characteristics of M. graminicola from rice fields in southern Vietnam and to evaluate the reaction of 20 rice varieties to this soil-borne pathogen in a glasshouse experiment. Ten populations of root-knot nematode collected from rice fields at different geographical regions in the Mekong Delta were identified as M. graminicola based on the perineal configuration of females and species-specific molecular markers. The morphological, morphometric and molecular characteristics of ten nematode isolates were defined, and the variations observed between these isolates were not significantly different. The pathogenicity of these isolates was examined in the susceptible Indica rice, Oryza sativa ‘IR64’, with a reproduction factor ranging from 18.1 to 37.8. Of the 20 Indica rice varieties tested in response to the nematode population MG-PN08, the ‘Tetep’ variety showed moderate resistance to the nematode (reproductive factor = 11.7; galling index = 2.4), while others were ranked at levels ranging from moderately susceptible to highly susceptible. The life cycle of M. graminicola in ‘Tetep’ root is 28 days compared to 21 in ‘IR64’. ‘Tetep’-nematode interaction at the histological and molecular levels needs further investigation to develop new rice varieties resistant to rice root-knot nematode.

Use of botanicals in root-knot nematode control: a meta-analysis

This meta-analysis was conducted to quantitatively analyze the efficacy of plant residues and plant derivatives of various plant species against root-knot nematodes (Meloidogyne spp.). Publications investigating root-knot nematodes control with plant-based amendments, i.e., plant residues (i.e., crop trash/stubble, pomace, oil cakes) and plant derivatives, such as extracts and powders of leaf, flower and fruit, were identified in Scopus® and ScienceDirect® databases and other literature. A meta-analysis was done by calculating the natural logarithm of response ratios of different plant-based soil amendments against root-knot nematodes. Plant residues reduced the number of root-knot nematode and its damage nearly by 49% compared to the control in general. Plant residues of Raphanus sativus (radish) and Oryza sativa (rice) demonstrated the highest root-knot nematode control, with up to 85% reduction in damage and root-knot nematode population densities when compared to the control. Leaf extracts of Allium tuberosum (garlic) and leaf powder of Laurelia sempervirens (Peruvian nutmeg) demonstrated the highest percentage reduction of root-knot nematode population densities and damage.

Potency of plant-derived biological nematicides on root-knot disease of tomato, Lycopersicon lycopersicum (L.) Mill

The aim of this research was to evaluate the effectiveness of plant-derived biological nematicides in the management of root-knot nematode disease of tomato. A piece of land measuring 8 m × 54 m was ploughed and raised beds were the experimental plots. The land was divided into 4 blocks, each block comprising 12 treatments and 4 replicates with a total of 48 experimental plots were fitted into randomized complete block design (RCBD). The experiment was carried out at the Teaching and Research Farms, Faculty of Agricultural Sciences, Ladoke Akintola University of Technology, Ogbomoso, Oyo State, Nigeria (Longitude 40E and Latitude 8010N) during 2018 planting season. 20 g macerated root gall of Celosia was applied to tomato root rhizosphere (inoculation). The plant-derived biological nematicides that were assessed on root-knot nematode disease of tomato, UC8 cultivar, include the leaf water extract of neem, castor, wild sunflower, cleome, siam weed, phyllanthus, nitta, tobacco, lantana and calotropis, mixed with black soap, at rate of 9:1 v/w. The black soap and distilled water served as adjuvant and solvent respectively, and as the control experiments. The results showed that the root galling and soil population of root-knot nematode were significantly reduced with consequent enhanced growth and yield of tomato in the plots treated with plant-derived biological nematicides, compared with the tomato in the control experiments. The study has demonstrated that the use of plant-derived biological nematicides can be effectively explored in the management of root-knot nematode disease. The application of plant-derived biological nematicides is therefore recommended for sustainable management of root-knot nematode disease in tomato production.

Estimation of avoidable yield losses due to root-knot nematodes, Meloidogyne spp. infesting okra [Abelmoschus esculentus (L) Moench

A field experiment was conducted during 2015-16 and 2016-17 at Anand Agriculture University, Anand (Gujarat) to estimate avoidable yield losses due to root-knot nematodes, Meloidogyne spp. infesting okra. The application of Carbofuran 3G @ 1.5 kg a.i ha-1 significantly enhanced the plant growth parameters and yield of okra with significant reduction in root-knot index and nematode population under field conditions. The avoidable yield loss recorded at the end of two years was 23.75% due to root knot nematodes in okra cv. GAO 5.

Soil Types and their Physio – Chemical Properties for Population Development of Root Knot Nematode (Meloidogyne spp.) in Tomato (Solanum lycopersicum)

Root Knot Nematodes (RKN) (Meloidogyne spp.) is the major soil borne microorganisms causing severe losses in vegetable production in Sri Lanka. This experiment was conducted to determine the effect of the fourteen different soil types and their physio-chemical properties for population development of Meloidogyne spp on tomato crop. The population of RKN showed significant differences among different soil types. The maximum nematode population (Root Galling Index of 7.25, Number of knots of 165.25) were recorded in Red Yellow Podzolic – Imperfectly Drained soil with higher organic carbon (11.54%), phosphorus (3.30 ppm), potassium (369 ppm), sand (77.06%), moisture content (16.22%) and it was not significantly difference between Red Yellow Podzolic – Imperfectly Drained soil and Regosol. The minimum nematode population (Root Galling Index of 2.75, Number of knots of 51.75) was recorded in Reddish Brown Latosol – Imperfectly Drained soil with organic carbon (4.1% w/w), phosphorus (0.58 ppm), sand (64.66%), and moisture content (6.19%). Analysis of correlation coefficient showed that population of Meloidogyne spp. significantly positive correlated with phosphorus, potassium, nitrogen, EC, soil moisture and sand percentage while significantly negative correlated with the silt + clay percentage, soil temperature and soil pH. There was no significant correlation recorded with soil organic carbon content as it was clearly indicated that all the samples had very low percentage of organic carbon in compared to suppressive soils. Therefore, the study concludes all soil physic-chemical properties except organic carbon have direct effect on the development of population of Meloidogyne spp. and it is varied with the different soil types, hence it is vital to contemplate soil type and its physio-chemical properties when executing Integrated Nematode management programs for Meloidogyne spp. However, further Investigations are required to study the direct effect of soil organic carbon on development of population of Meloidogyne spp.

Trichoderma asperellum affects Meloidogyne incognita infestation and development in Celosia argentea

Abstract Due to the rise in cost and detrimental health and environmental consequences that accompany the use of nematicides, there is a need for a more eco-friendly and less expensive alternative to control root-knot nematode (Meloidogyne incognita). Nematode infestation reduces the quality and quantity of Celosia argentea Linn. A pot experiment was conducted in a greenhouse to determine the biocontrol efficacy of Trichoderma asperellum against M. incognita in C. argentea. The treatments consisted M. incognita infected C. argentea inoculated with 0, 2.2 × 107, 4.4 × 107, or 6.6 × 107 cfu/pot of T. asperellum. All doses of T. asperellum reduced the root-knot nematode population and root gall index. Growth and development of C. argentea were improved, indicating that T. asperellum has the potential to be used as a biocontrol agent in C. argentea production. The biocontrol activity of T. asperellum in C. argantea increased as the week went by until the plants attained full maturity. Hence, the control of M. incognita by T. asperellum depends on the developmental stage of the plant root system.

Integration of some organic amendments and the predatory nematode, Fictor composticola, for the management of Meloidogyne incognita in cucumber

BackgroundOrganic amendments are well known for influencing soil nematode community structure, diversities, and activities. Most of the previous studies focused on effects of organic amendments on plant-parasitic nematodes, but only a few investigated the effect of combination of biocontrol agents and organic amendments on soil nematodes.Main bodyDifferent organic amendments (neem cake, poultry manure, and neem leaves) were combined with the predatory nematode, Fictor composticola, for the control of root-knot nematode, Meloidogyne incognita, in cucumber. Organic amendments were mixed in pots containing 1 kg soil, 15 days before sowing. Cucumber (cv. CCH-1) plants grown in these pots were inoculated by 2000 J2 of M. incognita and 400 F. composticola per pot, after 1 week of germination. Fictor composticola in combination with chicken manure + neem cake + neem leaves was found the best mixture for reducing the number of galls, egg masses, and final root-knot nematode population. The predator’s population reached the maximum in this treatment. All combinations of organic amendments in the presence of F. composticola were found significantly superior over inoculated check in reducing nematode’s population and in improving plant growth over the un-inoculated check.ConclusionsData indicated the suitability of using the predatory nematode, F. composticola, and organic amendments for potential use in sustainable nematode management strategies.

Surrounding the swollen roots of sweetpotato with a decomposing band of an organic amendment enhances nematode-suppressive services and reduces damage caused by root-knot nematode

A previous field trial showed that marketable yield increased and root-knot nematode populations declined when the swollen roots of sweetpotato were surrounded by a sawdust-based amendment. Further evidence that such amendments provide worthwhile levels of nematode control was obtained in this study. Customised pots filled with an organic amendment or amended soil were kept in a greenhouse or buried in the field for various times and then the nematode-control potential of various treatments was assessed by surrounding the pots with soil infested with Meloidogyne incognita. Swollen root production generally increased, and root-knot nematode populations consistently declined, when sawdust was used as an amendment. The addition of an organic nitrogen source generally improved the level of control. Laboratory and greenhouse assays confirmed that amended soils were biologically suppressive, as root-knot nematode numbers were lower and fewer galls were produced in soil containing decomposing amendments than in soil or sand that had been heated to kill the soil biota. A predatory nematode morphologically similar to Clarkus papillatus was one of the suppressive agents as numbers were very high in some experiments. Mesostigmatid mites in the family Laelapidae and genera Sejus, Protogamasellus, Holaspulus and Gamasiphis were also contributing, while an acarid mite (Rhizoglyphus robini) occurred in high numbers and was observed devouring root-knot nematode juveniles on agar plates. Nematophagous fungi were also involved as three species of nematode-trapping fungi (Arthrobotrys musiformis, A. thaumasia and A. oligospora) and an unidentified fungus that captures nematodes on bulbous hyphal extensions were consistently isolated from amended soils. These results suggest that sawdust-based amendments enhance the nematode-suppressive services provided by a wide range of predators.

Epigenetic and Metabolic Changes in Root-Knot Nematode-Plant Interactions.

Two wild-type field populations of root-knot nematodes (Mi-Vfield, Mj-TunC2field), and two isolates selected for virulence in laboratory on resistant tomato cultivars (SM2V, SM11C2), were used to induce a resistance reaction in tomato to the soil-borne parasites. Epigenetic and metabolic mechanisms of resistance were detected and compared with those occurring in partially or fully successful infections. The activated epigenetic mechanisms in plant resistance, as opposed to those activated in infected plants, were detected by analyzing the methylated status of total DNA, by ELISA methods, and the expression level of key genes involved in the methylation pathway, by qRT-PCR. DNA hypo-methylation and down-regulation of two methyl-transferase genes (CMT2, DRM5), characterized the only true resistant reaction obtained by inoculating the Mi-1.2-carrying resistant tomato cv Rossol with the avirulent field population Mi-Vfield. On the contrary, in the roots into which nematodes were allowed to develop and reproduce, total DNA was generally found to be hyper-methylated and methyl-transferase genes up-loaded. DNA hypo-methylation was considered to be the upstream mechanism that triggers the general gene over-expression observed in plant resistance. Gene silencing induced by nematodes may be obtained through DNA hyper-methylation and methyl-transferase gene activation. Plant resistance is also characterized by an inhibition of the anti-oxidant enzyme system and activation of the defense enzyme chitinase, as opposed to the activation of such a system and inhibition of the defense enzyme glucanase in roots infested by nematodes.

Molecular Characterization of an Emerging Root-Knot Nematode Meloidogyne enterolobii in North Carolina, USA.

An emerging threat to agriculture, Meloidogyne enterolobii Yang & Eisenback, 1983, is a tropical species and considered to be the most damaging root-knot nematode (RKN) in the world because of its wide host range, aggressiveness, and ability to overcome resistance to RKN in many crops. It was first detected in the United States on ornamental plants in Florida in 2001 but has since been identified in North Carolina, South Carolina, and Louisiana. Several thousand RKN populations were collected from North Carolina field crops, ornamental plants, and turfgrasses for species identification in the Nematode Assay Laboratory in the North Carolina Department of Agriculture & Consumer Services. From 2006 to 2019, root systems showing galling symptoms were dissected under the microscope, and females were obtained for DNA analysis. When only soil samples were submitted, the second-stage juveniles or males were used instead. Molecular characterization was performed via polymerase chain reaction with species-specific primers and DNA sequencing on the ribosomal DNA 18S-ITS1-5.8S and 28S D2/D3 and mitochondrial DNA CoxII-16S. One hundred thirty-five representative RKN populations from North Carolina were characterized and identified as M. enterolobii. Six populations from China where the species was originally described were included in this study for identity confirmation and comparison. As of December 2019, M. enterolobii has been confirmed from a limited number of fields in 11 North Carolina counties: Columbus, Craven, Greene, Harnett, Johnston, Lenoir, Nash, Pitt, Sampson, Wayne, and Wilson. Currently, M. enterolobii is the most important emerging RKN species in the United States and causes severe damage to agronomic and horticultural crops, especially sweetpotato in North Carolina.

Effect of pit-composting on root-knot nematode (Meloidogyne incognita and M. javanica) population densities and yield of tomato under field conditions

Soil amendments, constituting of various plant and animal sources, were evaluated in pits for their effects on Meloidogyne spp. infecting tomato in comparison to the synthetic nematicide fenamiphos and the untreated control. Fifty-six days after transplanting, soil and root samples were collected for nematode extraction and counting while fruit mass and the number of fruits were also recorded and the average yield per treatment calculated. The plant-based pit-composting treatments decreased nematode population densities, from 43% to 94%; with the citrus fruit-pit compost being the most effective (reducing nematode densities by up to 94%). Conversely, chicken and cattle manure treatments generally resulted in increased nematode densities (up to 141% and 159%, respectively). Increases in tomato yield ranged from 7% to 94% in response to compost, cattle and chicken manure treatments while all pit-composting significantly enhanced yield ranging from 100% to 400%; except for the shrub-pruning pit compost which decreased yield. Pit-composting is a promising strategy that can be used by especially subsistence farmers to grow crops sustainably in the presence of lower nematode pest densities.

Sustainable sweetpotato farming systems to improve soil health and reduce losses caused by root-knot nematode

Australia produces some of the highest sweetpotato yields in the world but the health of the soil used to produce the crop is declining because it is repeatedly tilled to kill volunteer sweetpotatoes, incorporate cover crop residues and prepare beds for planting. Additional disturbance occurs when the swollen roots are harvested. An on-farm study showed that it is possible to replace this tillage-dominated farming system with an alternative that is not only productive, but is also likely to be sustainable in the long-term. When the soil was amended with organic matter, beds were formed 10 months prior to planting, two cover crops (forage sorghum followed by oats) were grown on the beds, residues from those crops were retained on the soil surface as mulch, and sweetpotato cuttings were planted into the mulched, undisturbed beds using strip tillage, the crop established well and yielded 93 t/ha. The only detrimental effect was that root-knot nematode (Meloidogyne incognita) caused severe damage. In contrast, a trial in the same field showed that when organic amendments were placed in a furrow in the centre of the bed so that the swollen roots were surrounded by the amendment as they developed, nematode control was much better. Sawdust and a mixture of sawdust and chicken litter were the most effective amendments, as they both reduced root-knot nematode populations and the severity of nematode damage, and increased marketable yield by 29%. The wide range of natural enemies found in soil collected from the amended furrow at harvest, and the results of a suppression assay in the laboratory suggested that the soils amended with sawdust and sawdust /chicken litter were biologically suppressive to root-knot nematode.

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.

Management of Root Knot Nematode Meloidogyne incognita in Banana (Cv. Robusta) through Biocontrol Agents and Neem Cake

A pot culture experiment was performed to study the effect of native promising biocontrol agents and neem cake separately and in combination against root-knot nematode Meloidogyne incognita infecting banana cv. Robusta during 2016-2017. Treatments treated with bioagents and neem cake enhanced plant growth and root characters and suppressed root gall development in banana plant as compared to nematode alone and untreated control treatments. Among the various treatments, the combined application of Pseudomonas fluorescens @ 10 g/plant + Trichoderma viride @ 10 gm/plant + neem cake @ 100 gm/plant resulted in maximum increase of plant height (38.8 cm), number of leaves (7), pseudostem girth (15 cm), root length (25.6 cm), highest number of healthy roots (17.0), poor number of infected roots (3.3), lowest root gall index (1 scale) and significantly reduced root-knot nematode population both soil (55.0 nos) and roots (90.0 nos). The application of single bioagent either P.fluorescens @ 10 gm/plant or T.viride @ 10 gm/plant along with neem cake were also recorded highest plant growth parameters and poor nematode infestation when compared to nematode alone treated control plant.

Control of Root-Knot Nematode (Meloidogyne incognita) in Tomato (Solanum lycopersicum) Crop Using Siam Weed (Chromolaena odorata) Compost Manure

Abstract A field experiment was conducted at Landmark University Omu-Aran, Nigeria from June to November 2017 and repeated at the same time in the year 2018 on a nematode infested soil to evaluate the effects of different amounts of Siam weed compost on the performance of root-knot nematode (RKN) infested tomato. The compost was applied a week before planting as soil amendment at the amount of 0.0, 0.5, 1.5, and 2.0 t·ha−1, while carbofuran was applied at the rate of 3.0 kg·ha−1. Four weeks old tomato seedlings cultivar ‘Roma VF’, which is susceptible to RKN, was transplanted to already prepared soil. Results of the experiment showed that the compost, especially in the amount 2 t·ha−1 and carbofuran at 3 kg·ha−1, brought about significant reduction of the population of RKN in soil and roots, and a significant increase in the growth and yield of tomato. The result of the experiment showed that Siam compost can be used for the managing root-knot nematodes in tomato cultivation, as an environmentally safe factor.

First Report of Northern Root-Knot Nematode Meloidogyne hapla on Codonopsis pilosula in China

Worldwide, root-knot nematodes are among the most important plant-parasitic nematodes infecting and causing yield losses on many important plant species. They can cause extensive galling on plant roots, leading to serious economic losses (Azevedo de Oliveira et al. 2018). Codonopsis pilosula is used extensively in traditional Chinese herbal medicine and is a major economic crop in Gansu province. In the summer of 2019, a survey for plant-parasitic nematodes was conducted in Gansu province, northwest China. During the survey, 35 out of 76 fields of C. pilosula had plants exhibiting stunting, decline, and extensive galling on the secondary and tertiary roots. These are typical symptoms of infection by root-knot nematodes. Females, males, J2s, and eggs collected from roots of C. pilosula had the following morphometric characters: the perineal pattern of females (n = 10) were round-shaped, with low dorsal arches and small punctations near the anus, lateral line marked. Females (n = 20): body length (L) = 579.06 ± 50.19 μm (511.42 to 677.41 μm), maximum body width (W) = 423.81 ± 29.11 μm (396.72 to 467.41 μm), stylet length = 9.93 ± 0.88 μm (8.71 to 11.72 μm), distance from dorsal esophageal gland opening to the stylet knot (DGO) = 4.93 ± 0.42 μm (3.91 to 5.84 μm), stylet median bulb width (MBW) = 29.67 ± 3.61 μm (24.41 to 35.31 μm). Males (n = 10): L = 1,021.75 ± 106.38 μm (885.09 to 1,230.52 μm), stylet length = 17.15 ± 1.41 μm (15.27 to 19.89 μm), DGO = 5.04 ± 0.61 μm (4.24 to 5.83 μm), MBW = 9.82 ± 2.09 μm (7.11 to 14.24 μm), spicule length = 21.97 ± 1.67 μm (19.54 to 24.59 μm). J2s (n = 20): L = 363.66 ± 25.96 μm (322.41 to 398.88 μm), a = 24.41 ± 4.32 (21.33 to 27.12), stylet length = 10.41 ± 0.79 μm (9.01 to 11.32 μm), DGO = 4.01 ± 0.56 μm (3.22 to 5.13 μm), tail length = 53.15 ± 10.56 μm (32.74 to 71.24 μm). Eggs (n = 20): L = 73.92 ± 4.35 μm (68.43 to 80.13 μm), W = 25.19 ± 3.94 μm (20.48 to 30.74 μm). These morphological characteristics are consistent with Meloidogyne hapla Chitwood, 1949 as described by Whitehead (1968). Molecular analysis was conducted for further research; DNA was isolated from four individual females, and then the ITS region and D2/D3 region of 28S were amplified with primers18S/26S (Vrain et al.1992) and D2A/D3B (Al-Banna et al. 2004), respectively. The D2/D3 region of 28S sequence and ITS sequence were deposited in GenBank under accession numbers MN752204 and MN752202, respectively. D2/D3 region of 28S sequence was 99.84 to 99.91% identical to those of M. hapla from China (KJ755187), Myanmar (MN446015), and Japan (KF430798). The ITS region sequence was 99.31 to 99.61% identical to several sequences of M. hapla from GenBank, including ones from Spain (MH011978), Taiwan (KJ572385), the United States (AY268108), and Japan (LC030357). Furthermore, species identification was also confirmed using PCR to amplify with M. hapla-specific primers Mh-F/Mh-R (Feng et al. 2008). An expected PCR fragment of approximately 462 bp was obtained, which was consistent with M. hapla reported. No amplification products were observed in the control. A pathogenicity test of this M. hapla population was carried out in a growth chamber maintained at 20 to 25°C. Eight healthy C. pilosula seedlings were transplanted into plastic pots (one plant per pot). After 2 weeks, the roots of six plants were inoculated with 3,000 J2s and eggs per root system, and two uninoculated plants were used as a control. After 65 days, all inoculated plants exhibited yellowish leaves and stunting and had extensive galling on roots, which resembled those on field-grown plants. No galling or symptoms were observed on control plants. The final population density was quantified, and mean nematode reproduction factor (final population/initial population) was 4.3. These results confirm this root-knot nematode population on C. pilosula is M. hapla. To our knowledge, this is the first report of M. hapla in Gansu province and the first report of C. pilosula as a new host of M. hapla.

Morpho-molecular identification and pathogenicity test on fungal parasites of guava root-knot nematode eggs in Lampung, Indonesia

Abstract. Swibawa IG, Fitriana Y, Solikhin, Suharjo R, Susilo FX, Rani E, Haryani MS, Wardana RA. 2020. Morpho-molecular identification and pathogenicity test on fungal parasites of guava root-knot nematode eggs in Lampung, Indonesia. Biodiversitas 21: 1108-1115. This study aimed to obtain and discover the identity of the species of fungal egg parasites of root-knot nematodes (RKN), which have a high pathogenic ability causing major losses in vegetable crops. The exploration of the fungi was carried out in 2016 and 2018 from Crystal guava plantations in East Lampung, Central Lampung, Tanggamus, and NirAma, a commercial product that has been used for controlling Meloidogyne sp. in Indonesia. Identification was carried out based on morphological characteristics and molecular-based gene sequential analysis of Intergenic Transcribed Spacer (ITS) 1 and ITS 4. A pathogenicity test was carried out in vitro and in a greenhouse using tomato plants as indicator plants. In the in vitro test, observations were made on the percentage of infected RKN eggs. The observations in the greenhouse test were carried out on RKN populations in the soil and roots of tomato plants, root damage (root knots), and damage intensity due to RKN infection. The exploration resulted in five isolates of fungal egg parasites of RKN from the guava plantations in East Lampung (2), Central Lampung (1), Tanggamus (1), and from the isolation results of commercial products (1). The isolates were given codes as B4120X (PT GGP PG1), B3010 (PT GGP PG4), B412G (PT GGP PG 4), B01TG (Tanggamus), and BioP (Commercial products). Based on their morphological characteristics, the isolates were classified into the genus of Paecilomyces. The results of molecular identification showed that the discovered fungi were Purpureocillium lilacinum (Thom.) Luangsa Ard. (Syn. Paecilomyces lilacinus (Thom.) Samson.). Based on the in vitro tests, the five fungal isolates were able to parasitize RKN eggs at 86.4-100%. In the greenhouse test, all isolates significantly suppressed nematode populations in the soil and tomato roots, inhibited the formation of root knots, and produced lower damage intensity compared to controls. Among all the isolates tested, B01TG had the best ability to infect nematode eggs (99.5%), suppressing the formation of root knots, nematode population in the soil and the roots of tomato plants, and the damage intensity compared to other isolates.

The efficacy of molecular markers associated with virulence in root-knot nematodes

Summary Root-knot nematodes (Meloidogyne spp.) are major crop pests that cause heavy economic losses. The use of resistant cultivars is one of the most important management methods. The Mi-1 gene in tomato confers effective resistance against several species of Meloidogyne. However, Mi-1-virulent root-knot nematodes restrict the use of resistant cultivars. Molecular markers associated with virulence have been developed in previous studies but not validated in large number of Meloidogyne populations so far. In this study, molecular markers were screened in a total of 69 (a)virulent Meloidogyne incognita and M. javanica isolates. The results showed these markers did not separate virulent and avirulent populations from Turkey. In addition, polymerase chain reaction products obtained from primers HM1.F2/HM1.R2 were digested with 30 restriction enzymes but no differences among populations were found. To the best of our knowledge, this is the first report on screening large root-knot nematode populations with these markers.

Transcriptome Analysis of Rice Roots in Response to Root-Knot Nematode Infection.

Meloidogyne incognita and Meloidogyne graminicola are root-knot nematodes (RKNs) infecting rice (Oryza sativa L.) roots and severely decreasing yield, whose mechanisms of action remain unclear. We investigated RKN invasion and development in rice roots through RNA-seq transcriptome analysis. The results showed that 952 and 647 genes were differently expressed after 6 (invasion stage) and 18 (development stage) days post inoculation, respectively. Gene annotation showed that the differentially expressed genes were classified into diverse metabolic and stress response categories. Furthermore, phytohormone, transcription factor, redox signaling, and defense response pathways were enriched upon RKN infection. RNA-seq validation using qRT-PCR confirmed that CBL-interacting protein kinase (CIPK) genes (CIPK5, 8, 9, 11, 14, 23, 24, and 31) as well as brassinosteroid (BR)-related genes (OsBAK1, OsBRI1, D2, and D11) were altered by RKN infection. Analysis of the CIPK9 mutant and overexpressor indicated that the RKN populations were smaller in cipk9 and larger in CIPK9 OX, while more galls were produced in CIPK9 OX plant roots than the in wild-type roots. Significantly fewer numbers of second-stage infective juveniles (J2s) were observed in the plants expressing the BR biosynthesis gene D2 mutant and the BR receptor BRI1 activation-tagged mutant (bri1-D), and fewer galls were observed in bri1-D roots than in wild-type roots. The roots of plants expressing the regulator of ethylene signaling ERS1 (ethylene response sensor 1) mutant contained higher numbers of J2s and developed more galls compared with wild-type roots, suggesting that these signals function in RKN invasion or development. Our findings broaden our understanding of rice responses to RKN invasion and provide useful information for further research on RKN defense mechanisms.

Management of root-knot nematode, Meloidogyne incognita infesting fig under field conditions

A statistically designed field experiment with ten treatments including an untreated control replicated thrice in Randomized Block Design was conducted in root- knot nematode infested fig (cv. Poona fig) orchard. All the treatments were significantly superior over an untreated control in reducing root- knot nematode population, number of root galls and egg masses and increasing the yield of fig. However, soil application of carbofuran 3G at 2 kg a.i./ha was found to be most effective in reducing root-knot nematode population (53.66%), number of root galls (50.19%) and number of egg masses (45.36%) at intermediate stage and increasing the fruit yield of fig (37.85%) with 1:17.79 ICBR at termination. This treatment was followed by the treatment of phorate 10 G at 2kg a.i./ ha. The reduction in root- knot nematode population, number of root galls and egg masses and increase in fruit yield recorded in this treatment were 49.46, 50.11, 42.31 and 28.19%, respectively with 1: 33.64 ICBR. While, at termination stage, the treatment of Phule Trichoderma plus at 20 kg/ha was found to be most effective in reducing nematode population (40.36%), number of root galls (37.08%) and number of egg masses (41.02%) and increasing the fruit yield of fig (13.54%) with 1: 11.20 ICBR. This was followed by the treatments with rest of the biocontrol agents. The reduction in root- knot nematode population, number of root galls and number of egg masses and increase in fruit yield of fig recorded in these treatments ranged from 32.03 to 38.50, 29.31 to 36.00, 31.90 to 35.97 and 11.54 to 20.75%, respectively with 1: 9.80 to 1: 20.04 ICBR.