Rice Root-knot Nematode Research Articles

Molecular characterization of FMRFamide-like peptides in Meloidogyne graminicola and analysis of their knockdown effect on nematode infectivity

The rice root-knot nematode, Meloidogyne graminicola, seriously impairs the growth and yield of rice which is an important staple food worldwide. The disruption of neuropeptide signalling leading to attenuation in nematode behaviour and thereby perturbed infection, offers an attractive alternative to control nematodes. In this direction, the present study was aimed at mining of putative FMRFamide-like peptides (FLPs) from the transcriptomic dataset of M. graminicola followed by characterization of those FLPs via sequencing of PCR products, qRT-PCR and Southern hybridization analysis. We have characterized nine flp genes (flp-1, flp-3, flp-6, flp-7, flp-11, flp-12, flp-14, flp-16 and flp-18) and a partial neuropeptide receptor gene (flp-18 GPCR) from M. graminicola in the present study. In addition, in situ localization revealed the expression of flp-1 and flp-7 in neurons posterior to the circumpharyngeal nerve ring of M. graminicola. In vitro silencing of nine flp genes and flp-18 GPCR in M. graminicola J2 and their subsequent infection in rice and wheat roots demonstrated the reduced penetration ability of FLP silenced worms which underscores the potential of the FLPergic system as a broad-spectrum target to manage the root-knot nematode problem in rice-wheat cropping system.

Detection and molecular characterization of the rice root-knot nematode Meloidogyne graminicola in Italy

The rice root-knot nematode Meloidogyne graminicola was detected in North Italy attacking roots of rice plants in lowland and upland fields. This nematode was previously reported only in South and Southeast Asia, China, South Africa, United States, Columbia and Brazil attacking rice and wheat. The present study provides an integrative diagnosis of the nematode on the basis of morphological and molecular data by sequencing the SCAR species specific marker, the ITS region and the partial mitochondrial coII-16srRNA genes. Morphological and morphometric traits of the new intercepted population of M. graminicola agree with the original description. The diagnostic SCAR marker was amplified showing the expected size fragment and unequivocally identified the Italian population as M. graminicola. Sequence analyses of ITS and coII-16SrRNA confirmed this identification. Sequence comparison of both molecular markers among Italian M. graminicola populations from lowland and upland rice fields revealed 100% identity. Phylogenetic analysis based on the ITS and coII-16SrRNA sequences revealed that Italian M. graminicola formed a well supported cluster with M. graminicola populations from GenBank confirming the high intraspecific variability among all populations. No correlation between genetic variability and geographic origins occurred. Furthermore, the phylogenetic trees suggest a common ancestor for most of the facultative meiotic parthenogenetic Meloidogyne species.

Rice Root-knot Nematode Down Regulates GA-Gene to Establish Infection

Experiments were conducted to observe the role of gibberellin (GA) in the response of rice to infection by rice root-knot nematode, Meloidogyne graminicola. Gibberellin might have a negative effect on defence in Nipponbare against M. graminicola. On the other hand, an inhibitory effect to M. graminicola in Taichung 65 (wild type) was found when GA was applied exogenously. Galling was significantly and reproducibly lower in mutants, whether it was GA insensitive or GA deficient, than in Taichung 65. There were even significantly lower galls in these GA deficient mutants after GA treatment than in non-treated mutant plants. The expression of GA signaling gene Osgid1-7 was significantly higher only in whole root at 2 dpi (days post inoculation) but not in leaves or root tips. Even this gene was not differentially expressed in root and leaf tissues at later stage (6 dpi days post inoculation) of infection. The nematode inhibited biosynthesis of OsGA20ox in leaves at 2 dpi and, in both of leaves and roots at 6 dpi. The GA response gene AK073385 was also less expressed in root tip at 6 dpi (days post inoculation). These might help M. graminicola to continue their infection in Taichung 65.

Molecular mapping of rice root-knot nematode (Meloidogyne graminicola) resistance gene in Asian rice (Oryza sativa L.) using STMS markers

Rice root-knot nematode, Meloidogyne graminicola is one of the major pests of rice cropping system and is responsible for considerable yield reductions. Out of various management options tried so far, the resistance against M. graminicola in rice could be the most valuable in alleviating this problem. In present study a rice cultivar Abhishek exhibited a strong resistance with least number of galls (2galls/plant) and a kind of necrotic browning of roots which is typical of R-gene mediated resistance response. In order to map the gene governing resistance to root-knot nematode, the cultivar Abhishek was crossed with the Bangla Patni, a highly susceptible genotype to generate F2 mapping population. Using bulked segregant analysis, a marker HvSSR10–21 was identified to be putatively linked with the resistant locus in cv. Abhishek with significant LOD score. The significant LOD score value indicates the linkage between identified marker and the resistant locus against M. graminicola. We designate this gene as Mg1(t).

Host status of rotation crops in Asian rice-based cropping systems to the rice root-knot nematode Meloidogyne graminicola

Rotation with nonhost crops is an important practice used for root-knot nematode (RKN) management. Screenhouse experiments were conducted to evaluate the response infection of 27 cultivars belonging to 14 crops (blackgram, cabbage, cauliflower, chickpea, cowpea, garlic, ginger, greengram, groundnut, maize, potato, sesame, soybean, sunflower), which are grown in rotation with rice in lowland and upland rice-based ecosystems, to the RKN Meloidogyne graminicola. Root galling indices observed on all crop rotation cultivars were significantly lower compared with the rice cv. Thihtatyin, used as positive control. Differences in host response to M. graminicola infection were observed between cultivars. All 27 cultivars were poor or non-hosts of M. graminicola, except cv. Yezin 4 of chickpea considered as good host. No significant differences in plant growth were observed between non-inoculated and inoculated plants of all plant/species cultivars, with the exception of a reduction in root length in the chickpea cv. Yezin 4 (good host) and the garlic cv. Shan (poor host). Rotation crops identified as poor or non-hosts of M. graminicola could be useful in the management of RKN in rice-based cropping systems.

Interactions between the oomycete Pythium arrhenomanes and the rice root-knot nematode Meloidogyne graminicola in aerobic Asian rice varieties.

BackgroundAerobic rice fields are frequently infested by pathogenic oomycetes (Pythium spp.) and the rice root-knot nematode Meloidogyne graminicola. Here, the interaction between Pythium arrhenomanes and Meloidogyne graminicola was studied in rice roots of two aerobic rice varieties. In different experimental set-ups and infection regimes, plant growth, rice yield, Pythium colonization, as well as establishment, development and reproduction of M. graminicola were studied.ResultsIn this study, it is shown that the presence of P. arrhenomanes delays the establishment, development and reproduction of M. graminicola compared to single nematode infected plants. The delay in establishment and development of M. graminicola becomes stronger with higher P. arrhenomanes infection pressure.ConclusionsOur data indicate that P. arrhenomanes antagonizes M. graminicola in the rice root and that the plant benefits from this antagonism as shown by the yield data, especially when either of the pathogens is present in high levels.Electronic supplementary materialThe online version of this article (doi:10.1186/s12284-016-0108-3) contains supplementary material, which is available to authorized users.

The development and molecular characterization of a rapid detection method for Rice root-knot nematode (Meloidogyne graminicola)

The root-knot nematode Meloidogyne graminicola is a major constraint in rice production in the world. Using rDNA-ITS sequences data alignments, the genetic variation among twenty-one populations of M. graminicola (sixteen from Myanmar and five from China) was investigated. The results showed that all the populations were clearly separated from other species and that there was a low level of genetic variation among the isolates. A set of species-specific primers was designed to develop a species-specific molecular tool for the precise identification of M. graminicola. The primer reliability, specificity and sensitivity tests showed that the primer set (Mg-F3 and Mg-R2) amplified the expected fragment size of 369 bp from the template DNA of target nematode populations but not from non-target organisms. A duplex PCR test allows for saving diagnostic time and costs by amplifying the species of interest from a nematode mixture. Therefore, this species-specific primer set may be a powerful tool to improve taxonomic identification by non-specialists and the design of successful management practices as well.

Development of real-time PCR primers for the quantification of Meloidogyne graminicola, Hirschmanniella oryzae and Heterodera cajani, pests of the major crops in Myanmar

The rice root-knot nematode,Meloidogyne graminicola, and the rice root nematode,Hirschmanniella oryzae, are soil-borne pests causing damage to rice, and the pigeon pea cyst nematode,Heterodera cajani, is a pest to beans and sesame. Real-time PCR primers were designed for quantification. Relationships between the threshold cycle (Ct:y) values and number (no.) of nematodes inoculated () were:M. graminicola: ;H. oryzae: ; andH. cajani: .Meloidogyne graminicolaandH. oryzaewere detected in 25 and 38 out of 50 soils, collected from different fields in the lowland and central area of Myanmar, and their densities ranged from 1.0 to 4779 and from 0.4 to 787 (20 g soil)−1, respectively, whileH. cajaniwas detected only in two fields (3 and 268 (20 g soil)−1). The DNA-based method enables rapid and reliable quantification of the nematodes in soil.

Host response of Oryza glaberrima and O. sativa rice genotypes to the rice root-knot nematode Meloidogyne graminicola in a hydroponic system under growth chamber

The host response of 25 rice genotypes belonging to Oryza glaberrima and Oryza sativa to Meloidogyne graminicola infection was examined in a hydroponic system. The M. graminicola can build up high population densities in a hydroponic system. Resistance to this nematode species was found in O. glaberrima genotypes which supported significantly lower nematode numbers per plant and per unit root than O. sativa genotypes. The M. graminicola-infected O. sativa genotypes showed a higher root galling index than the O. glaberrima genotypes. The hydroponic system is efficient and reliable method to examine the host response of rice genotypes to M. graminicola infection, and can be useful for the fast screening of high numbers of rice genotypes for the selection of M. graminicola-resistant rice germplasm for breeding purposes.

β-Aminobutyric Acid-Induced Resistance Against Root-Knot Nematodes in Rice Is Based on Increased Basal Defense.

The nonprotein amino acid β-aminobutyric acid (BABA) is known to protect plants against various pathogens. The mode of action is relatively diverse and specific in different plant-pathogen systems. To extend the analysis of the mode of action of BABA to plant-parasitic nematodes in monocot plants, we evaluated the effect of BABA against the root-knot nematode (RKN) Meloidogyne graminicola in rice. BABA treatment of rice plants inhibited nematode penetration and resulted in delayed nematode and giant cell development. BABA-induced resistance (BABA-IR) was still functional in mutants or transgenics defective in salicylic acid biosynthesis and response or abscisic acid (ABA) response. Pharmacological inhibition of jasmonic acid (JA) and ethylene (ET) biosynthesis indicated that BABA-IR against rice RKN likely occurs independent of JA and ET. However, histochemical and biochemical quantification in combination with quantitative real-time reverse transcription-polymerase chain reaction data suggest that BABA protects rice against RKN through the activation of basal defense mechanisms of the plant, such as reactive oxygen species accumulation, lignin formation, and callose deposition.

English

Of late, rice root-knot nematode Meloidogyne graminicola has become a serious menace in all type of rice situations in India. A field study was under taken during kharif-2013 to evaluate 135 landraces (local cultivars) collected and maintained at Organic Farming Research centre of ZAHRS, Navile, Shimoga against Meloidogyne graminicola. The result reveals that the varieties show varying degrees of responses. Out of 135 cultivars, 32 cultivars were found to be highly resistant, while, 45 varieties read were resistant. However, 40 varieties were evaluated to be moderately resistant and nine varieties susceptible. The remaining nine cultivars were learnt to be highly susceptible. Key word: Rice, root-knot nematode.

Histopathological changes and evaluation of resistance in Asian rice (Oryza sativaL.) against rice root-knot nematode,Meloidogyne graminicolaGolden & Birch.

The rice root-knot nematode, Meloidogyne graminicola is one of the major pest of the rice-wheat cropping system, and is responsible for considerable yield reductions. Resistance against M. graminicola in rice could be most valuable in alleviating this problem. In the present study, 64 rice cvs./landraces were evaluated for resistance against rice root-knot nematode on the basis of root-knot index. Our study showed a large variation in susceptibility and sensitivity to M. graminicola infection among the rice cvs./landraces examined. Out of the total 64 rice cvs., seven (Abhishek, Khaja, Super Sugandhamati, Kishori Dehraduni, Gaudeshwari, Tuniaslet, Chima Kamin) had less than 10 galls/plant and of these, Abhishek exhibited a strong resistance response with least number of galls (2 galls/plant) and necrotic browning of roots. The nematode females in the roots of cv. Abhishek were smaller in size compared to those on the highly susceptible cv. Bangla Patni. The histopathological studies showed that the giant cells collapsed and degenerated before the J2s developed into adults. The resistant trait exhibiting rice cultivar, Abhishek, holds promise for resistance breeding and also for identifying resistance gene/s against M. graminicola.

Life cycle of the rice root-knot nematode Meloidogyne graminicola at different temperatures under non-flooded and flooded conditions

The life cycle of the rice root-knot nematode, Meloidogyne graminicola, was studied in an indoor growth chamber on the susceptible Asian rice cultivar UPLRi-5 at 29/26 and 36/32 °C (day/night temperature) under non-flooded and flooded conditions. Adult females were observed 11 days after inoculation (DAI) at 36/32 °C under non-flooded conditions and at 29/26 °C under flooded conditions. At 29/26 °C under non-flooded conditions, adult females were observed at 13 DAI. Completion of the life cycle from the second-stage juvenile (J2) to the second-generation J2 at 29/26 °C under non-flooded conditions was 20 days, and 19 days at 29/26 and 36/32 °C under flooded and non-flooded conditions, respectively. At 36/32 °C under non-flooded conditions, about one-third more adult females were observed compared with the other treatments but this did not result in more second-generation J2. The number of second-generation J2 was significantly higher (more than 15 times) at 29/26 °C under flooded conditions compared with the other treatments. At 25 DAI (i.e. after the second-generation J2 had been generated), a significant 3.5 fold increase in the number of galls per root system was observed on the plants grown at 29/26 °C under non-flooded conditions compared with the other treatments.

Evaluation of the host response of lowland and upland rice varieties from Myanmar to the rice root-knot nematode Meloidogyne graminicola

The rice root-knot nematode Meloidogyne graminicola is considered one of the most potentially important nematode pathogens of rice, especially in South and Southeast Asia, in a range of rice production systems. Identification of M. graminicola-resistant or -tolerant rice varieties will enable breeding programmes to develop rice varieties which are able to limit yield losses caused by this nematode species. The host response to M. graminicola infection of 15 lowland rice varieties and 9 upland rice varieties, which are being grown in the summer-irrigated lowland and rainfed upland rice ecosystems in Myanmar, was evaluated in two experiments under screenhouse conditions. The lowland rice experiment was carried out under intermittently flooded conditions in a clay loam soil (i.e. simulating the summer-irrigated lowland rice ecosystem) and the upland rice experiment was carried out at field capacity in a sandy loam soil (i.e. simulating the monsoon rainfed upland rice ecosystem). None of the15 lowland and 9 upland rice varieties were resistant to M. graminicola infection although differences in susceptibility and sensitivity were observed. Six (or 40%) out of the 15 lowland varieties examined were classified as less susceptible (LS) to M. graminicola infection, five (or 33.3%) as moderately susceptible (MS) while four (or 26.7%) as highly susceptible (HS). One (or 11.1%) out of the nine upland varieties examined was classified as LS to M. graminicola infection, three (or 33.3%) as MS while five (or 55.6%) as HS. Five (or 33.3%) out of the 15 lowland varieties examined were classified as either less sensitive or tolerant to M. graminicola infection. One (or 11.1%) out of the nine upland varieties examined was classified as tolerant to M. graminicola infection. This study offers interesting information for the farmer regarding which rice variety should be grown in M. graminicola-infested fields under either lowland or upland conditions.

Host response of rice genotypes to the rice root-knot nematode (Meloidogyne graminicola) under aerobic soil conditions

Aerobic rice is a production system where adapted rice varieties are established via direct seeding in non-puddled, non-flooded, non-saturated fields and grown under conditions similar to upland conditions. On land cultivated continuously with aerobic rice, a yield reduction has been observed. The rice root-knot nematode Meloidogyne graminicola is considered one of the possible causes of these yield reductions. Resistance to and tolerance for M. graminicola are essential traits for aerobic rice cultivars in alleviating this problem. In our study, the host response of nineteen aerobic, seven upland and four lowland rice genotypes which are either being used in the International Rice Research Institute’s aerobic rice breeding programme or already cultivated by farmers in Asia was evaluated under aerobic soil conditions in an outdoor raised-bed experiment. Our study showed a large variation in susceptibility and sensitivity to M. graminicola infection among the rice genotypes examined. Resistance comparable to the resistant reference genotypes included in the experiment (CG14, TOG5674, TOG7235) was not found but in terms of susceptibility, the upland genotype Morobereken may be an interesting less-susceptible genotype. Tolerance was found and in terms of sensitivity, the high yielding aerobic genotype IR78877-208-B-1-2 may be an interesting tolerant genotype. Our study also allowed the identification of rice genotypes that are either highly susceptible or sensitive to M. graminicola infection and of which the cultivation should be discouraged. On average, M. graminicola caused an almost 30% reduction in yield. Excluding the two susceptible and three resistant reference genotypes included in the experiment, most affected was dry-shoot biomass (23.6% reduction) followed by root length, which was more affected than fresh-root weight (19.8 vs. 8%) and grain filling (17.3%), while plant height and the number of spikelets/panicle were less affected (10.2 and 8.1%, respectively). Neither tillering nor the number of panicles/plant were affected.

Population dynamics of Meloidogyne graminicola and Hirschmanniella oryzae in a double rice-cropping sequence in the lowlands of Myanmar

The rice root-knot nematode, Meloidogyne graminicola, and the rice root nematode, Hirschmanniella oryzae, are considered potentially important nematode pathogens in lowland rice. A study was undertaken from December 2009 until December 2010 in the Ayeyarwady River Delta, the major lowland rice-producing area of Myanmar, to monitor the population dynamics of M. graminicola and H. oryzae in a naturally infested field. Root samples of the two rice varieties Yatanartoe and Taungpyan that are commonly cultivated in double rice-cropping sequences in Myanmar and represent irrigated and rainfed lowland rice varieties, respectively, were obtained for nematode analysis. During the summer-irrigated rice-growing season the root population density of second-stage juveniles (J2) of M. graminicola showed two distinct peaks – at the maximum tillering stage of the rice plants in January and at the heading stage of the rice plants in March 2010. With the onset of the monsoon rains, the J2 population densities in the roots of ratoon rice plants gradually decreased in May. During the rainfed monsoon rice-growing season, very low population densities of M. graminicola J2 were detected in the roots of rice plants, while the root population density of H. oryzae juveniles and adults showed two distinct peaks – at the maximum tillering stage of the rice plants in August and at the heading stage of the rice plants in October 2010. With the onset of the dry season, population density of H. oryzae in the roots reached the lowest density at harvest in November. Root galling caused by M. graminicola followed the same trend as the J2 population densities throughout the irrigated season. No root galls were observed during the monsoon season. Our results can be used for practical purposes aimed at a better management of both M. graminicola and H. oryzae.

Meloidogyne graminicola and Sclerotium rolfsii interaction in rice

Rice root-knot nematode Meloidogyne graminicola causes yield losses of up to 18% in rainfed upland rice in eastern India, and seedling blight disease of rice, caused by Sclerotium rolfsii , is seen to be associated with it (Mathur 1973). This observation led to the investigation of the nature and type of association among rice cultivar IR8, M. graminicola , and S. rolfsii . Samples of IR8 plants with an intact root system and rhizosphere soil collected from the 0-5-cm depth of a rainfed upland rice field served as a source of inoculum for the greenhouse experiments.

Global status of rice root-knot nematode, Meloidogyne graminicola

In the recent past, rice root-knot nematode, Meloidogyne graminicola has attained wide importance due to its potential to cause major damage in rice-wheat cropping system. It has become an emerging problem in the nurseries and upland rice along with its widespread occurrence in the deepwater and irrigated rice in the different countries of Southeast Asia. Second stage juveniles (J2s) penetrate the roots closely behind the root tip; migrate to vascular cylinder turning it into multinucleated giant cells, by endomitosis and cell hypertrophy characterized by hook shaped galls. This nematode is remarkably well adapted to flooded condition as it can survive in the aerenchymatous tissue of the graminaceous plant in flooded condition. Key words: Continents, incidence, loss/damage, rice-wheat cropping sequence.

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.

Comparison of migration, penetration, development and reproduction of Meloidogyne graminicola on susceptible and resistant rice genotypes

Migration, penetration, development and reproduction of the rice root-knot nematode, Meloidogyne graminicola, in the resistant African rice genotypes TOG5674, TOG5675, CG14 and RAM131, and in the susceptible Asian rice genotypes IR64 and UPLRi-5 were studied and compared. The number of second-stage juveniles (J2) that had migrated horizontally and vertically towards the rhizosphere at 48 h after inoculation was comparable in both resistant and susceptible rice genotypes. Penetration of J2 was significantly lower in the resistant rice genotypes compared with the susceptible rice genotypes at 3 and 7 days after inoculation (DAI). Nematode development in the resistant rice genotypes was slower than in the susceptible rice genotypes. Nematode reproduction was significantly lower in the resistant rice genotypes, which supported fewer eggs per g of roots and eggs per female. A significantly higher percentage of egg-laying females was found in the susceptible rice genotypes. Mature females that had developed in the resistant rice genotypes were significantly smaller than the ones in the susceptible rice genotypes. The resistant rice genotypes had significantly fewer galls than the susceptible rice genotypes.