Density Of Plant-parasitic Nematodes Research Articles

Distribution and population density of plant parasitic nematodes in Kallakurichi, Vedaranyam and Bargur blocks of Tamil Nadu

India contribute 9 per cent share in world production and one of the main vegetables grown in Tamil Nadu. Major production area of Tamil Nadu is Coimbatore, Dharmapuri, Salem and Krishnagiri districts. In India an average, a national loss of Rs. 21,068.73 millions has been estimated due to plant parasitic nematodes. An overall average annual yield loss in major horticultural crops due to nematodes goes upto 60% under protected cultivation. Protected cultivation is an emerging technology for raising vegetable and flower crops under controlled environmental condition and continuous growing of crops. Plant parasitic nematodes has emerged as a major problem, causing enormous yield loss. The maximum population of Pratylenchus spp in soil and root (300.54 and 275.50) were recorded in Veerasolapurammadur village, Kallakurichi block in sugarcane eco system and maximum lesion index 5.0 was recorded in same location and no incidence for root knot nematode was recorded. In Vaedharanyam block, The maximum population of Melodogyne graminicola in soil and root (300.25 and 325.65) were recorded in Neivellakku village, Vedharanyam block in rice eco system and maximum root knot index 5.0 was recorded in same location and no incidence for Aphelenchoides besseyi was recorded. In Barugur block ,The maximum population of lesion nematode, Radopholus similis in soil and root (450.20 and 410.25) were recorded in Santhur village, burgur block in banana eco system and maximum root lesion index 5.0 was recorded in same location and minimum population of root knot nematode (110.20 and 120.54) was recorded in Errapatty village of Burgur block.

Distribution and population density of plant parasitic nematodes in Kallakurichi, Vedaranyam and Bargur blocks of Tamil Nadu

Distribution and population density of plant parasitic nematodes in Kallakurichi, Vedaranyam and Bargur blocks of Tamil Nadu

Abundance and diversity of terrestrial free-living nematodes in potato agroecosystem

Abstract. Mutala’liah, Manan A, Bayyinah LN. 2023. Abundance and diversity of terrestrial free-living nematodes in potato agroecosystem. Nusantara Bioscience 15: 129-136. The presence of terrestrial free-living nematodes in agroecosystems is frequently overlooked. However, these microorganisms in agroecosystems soil are beneficial for supporting plant growth. These microorganisms could recycle the nitrogen in soil, decomposition and mineralization of organic matter, and suppress the densities of plant parasitic nematodes through their life strategy. Terrestrial free-living nematodes are classified according to trophic groups such as bacterivores, fungivores, predators, and omnivores. Reports on the abundance and diversity of terrestrial free-living nematode populations in agroecosystems, especially on potato plantations, were limited. They usually focused on the plant parasitic nematode’s attack on potatoes. Therefore, this study aimed to examine the diversity and abundance of terrestrial free-living nematodes in potato agroecosystems. The current study was conducted in two potato fields in Pratin Village, Serang, Purbalingga, Central Java, Indonesia. Soil samples were collected from two potato fields planted with different varieties (Granola and Atlantik) and extracted using the Whitehead-tray method. The variables observed were the diversity of genera and the abundance of terrestrial free-living nematode populations from each field. Population density data were analyzed by T-test, and diversity (H'), evenness (E), and dominance index (D) were also calculated. The results showed that the mean population densities of terrestrial free-living nematodes in the two fields were significantly higher at 918.40 individuals/ 100 g of soil in the Atlantik field than in the Granola field 76.53 individuals/ 100 g of soil. However, the diversity, evenness, and dominance index were not significantly different in both fields. Genera of nematode found in the Granola field were Diplogaster, Dorylaimus, Trypilla, and Lotonchus, while in the Atlantik field were Rhabditis and Dorylaimus.

Interspecific interactions between crops influence soil functional groups and networks in a maize/soybean intercropping system

Despite increasing evidence that intercropping systems may increase crop productivity, little is known about whether and how soil biota change under interspecific competition among plants. A field experiment with maize/soybean intercropping and the corresponding monoculture systems was conducted under four nitrogen fertilization regimes to investigate the effects of interspecific plant interactions on grain yield, soil properties (β-glucosidase and water-soluble carbohydrates), and biotic communities (bacteria, fungi, and nematodes). The soils under maize and soybean in the intercropping system were sampled separately to represent intercropped maize and intercropped soybean, respectively. Compared to monocultures, the complexity and robustness of soil networks comprising bacterial, fungal, and nematode communities increased in intercropped maize soils, but densities of plant parasitic nematodes and β-glucosidase activity were reduced. Intercropped soybean soils had lower C availability due to chronic shading by maize, but a significant increase was found in saprophytic fungi, and plant parasitic nematodes compared to soybean monoculture soils. Although intercropped soybean suffered from interspecific competition with maize, the interactions within the fungal community increased for both crop species in the intercropping system. Our study demonstrates that increased carbon uptake in maize due to increased light capture in the intercropping system can facilitate nutrient cycling by altering the abundance of functional groups of soil organisms, such as saprophytic fungi, and enhancing network complexity and stability. We detected a trade-off between productivity and soil nematode diversity in the intercropping system under nitrogen fertilization, the yield of maize increased but soil nematode richness decreased at low nitrogen level, while the yield of soybean decreased but the nematode richness increased at high nitrogen level. These findings show that both trade-offs and benefits occur in intercropping systems and highlight the role of plant-soil biota interactions in such systems.

Frequency Occurrence and Population Density of Plant-Parasitic Nematodes Associated with Solanaceous Plantations Grown in Dakahlia Governorate

Frequency Occurrence and Population Density of Plant-Parasitic Nematodes Associated with Solanaceous Plantations Grown in Dakahlia Governorate

Distribution and population density of plant parasitic nematodes on cereal production areas of Isparta and Burdur Provinces of Turkey

Plant parasitic nematodes were systematically surveyed in cereal production areas of Isparta and Burdur Provinces of Turkey in 2016-2017. Nine plant parasitic nematode genera were identified in Isparta and Burdur [Ditylenchus (23%), Geocenamus (20%), Helicotylenchus (33%), Heterodera (<1%), Meloidogyne (3%), Pratylenchus (76%), Pratylenchoides (52%), Paratylenchus (41%) and Tylenchus (18%)]. Pratylenchus spp. was found in 82% and 68% of samples, and Pratylenchoides spp. in 55% and 63% samples in Isparta and Burdur Province, respectively. The densities of Pratylenchus and Pratylenchoides species were higher in Isparta than in Burdur, and were often over the threshold for economic damage. As a result of morphological diagnostic studies, Pratylenchus crenatus Loof, 1960, Pratylenchus neglectus (Rensch, 1924) Filipjev & Schuurmans-Stekhoven, 1941, Pratylenchus penetrans (Cobb, 1917) Filipjev & Schuurmans-Stekhoven, 1941, Pratylenchus thornei Sher & Allen, 1953 (Tylenchida: Pratylenchidae), Pratylenchoides alkani Yüksel, 1977, Pratylenchoides crenicauda Winslow, 1958, Pratylenchoides erzurumensis Yüksel, 1977, Pratylenchoides leiocauda Sher, 1970, Pratylenchoides ritteri Sher, 1970 and Pratylenchoides variabilis Sher, 1970 (Tylenchida: Merliniidae) were identified. Pratylenchoides alkani, P. erzurumensis, P. neglectus and P. thornei were the most common species in wheat and barley fields in Burdur and Isparta Provinces.

NEMATODE SURVEY OF PLANTAIN ORCHARDS IN JATAÍ AND PEROLÂNDIA - GOIÁS, BRAZIL

Banana is an important fruit for Brazil, it is the most purchased in natura . Unfortunately, as every cultivated plant, banana trees have their yield-limiting pests and diseases. Among the most detrimental are the nematodes, which are sadly also ubiquitous in banana producing areas. In Jataí and Perolândia (GO) there is few data regarding the genera and population densities of plant parasitic nematodes in banana orchards. Therefore, a survey from 17 orchards is presented in this paper. All of them had plantains (AAB) planted, since it is the prevalent cultivated genetic group in the region. The nematode extraction method consisted in sieving followed by centrifugal separation. Together with the nematode survey a poll was presented to farmers, which encompassed questions about the general orchard management. Helicotylenchus was the prevailing genus in all samples. Meloidogyne and Pratylenchus also presented high population density in some areas.

Fertilizer application enhances establishment of cacao seedlings in plant-parasitic nematodes infected soil

Low soil fertility, pests and diseases are major problems of growth and establishment of cacao seedlings on the field. Cocoa production increases by new plantings and rehabilitation of moribund farms, but a build-up of plant-parasitic nematodes (PPN) causing dieback and declining soil fertility has discouraged many farmers, leading to a reduction in crop productivity. In this study, the potentials of some organic wastes as fertilizers and their effects on establishment of cacao seedlings in PPN infected soils was investigated at Ibadan and Owena of Southwestern Nigeria. Goat dung (GD), organic fertilizer (OF), organo-mineral fertilizers (OMF) and NPK 15:15:15 were applied at 200, 400 and 600 kg ha-1, respectively, to cacao seedlings one month after transplanting, while unfertilized served as control. Results from the experiments showed a significant increase in percentage survival of cacao seedlings under organic fertilizers at Ibadan and Owena compared to NPK and control even at the lowest rate of 200 kg ha-1 3 years after transplanting. The incorporation of GD, OF and OMF significantly reduced the population densities of PPN compared to control. Therefore, GD, OF and OMF at 200 kg ha-1 are recommended for soil application to enhance the field establishment of cacao seedlings in the soil infected with PPN.

INFLUENCE OF SOIL PROPERTIES ON PLANT NEMATODE POPULATION DENSITY UNDER Chromolaena odorata FALLOW

Relationships between soil abiotic factors and population densities of plant parasitic nematodes spe-cies under planted fallow of Chromolaena odorata was investigated for 2 years. Soil samples were collected at 0 – 30 cm depth to determine population of nematode species and soil physico-chemical properties was done at test initiation and afterwards at 6 months interval for 2 years. Four genera of plant parasitic nematode species (Meloidogyne spp., Pratylenchus spp, Helicotylenchus spp. and Xiphinema spp) and two free – living (Rhabditids and Dorylaimus spp.) were identified in the fallow. Soil organic Matter and soil N were significantly higher at 2 years than at 6, 12 and 18 months. Popu-lation density of plant parasitic nematode species significantly reduce as the fallow period extend reaching minimum at 2 years of fallow. Highest percentage reduction of 90.3 % was observed in popu-lation of Xiphinema at 2 years of fallow, followed by Pratylenchus with 51.5 % reduction in population and lowest reduction of 44 % was observed in Meloidogyne population. Negative and significant rela-tionship existed between soil physico-chemical properties and population density of plant parasitic nematode species indicated that soil characteristics play an important role in the abundance, distribu-tion and structure of nematode communities.

Responses of the citrus nematode population densities post-application of Nemarioc-AL phytonematicide and aldicarb synthetic nematicide

Density-dependent growth patterns suggested that under phytonematicides population densities of plant-parasitic nematodes could either be stimulated, neutral or inhibited, thereby resulting in ‘inconsistent results' concept. The objective of this study was to determine whether post-application sampling of the citrus nematode (Tylenchulus semipenetrans Cobb) population densities under untreated control, Nemarioc-AG phytonematicide and aldicarb on rough lemon (Citrus jambhiri Lush. ) seedlings could provide quantitative evidence of ‘inconsistent results'. Uniform three-month old C. jambhiri seedlings in plastic pots containing 2700 ml growing mixture were each inoculated with 10000 T. semipenetrans eggs and second-stage juveniles (J2). A week after inoculation, seedlings were split into three groups of seventy each and subjected to once-off treatment of untreated control, 2 g Nemarioc-AG phytonematicide and 2 g aldicarb. Five seedlings from each group were randomly placed on greenhouse benches to serve as a sampling block, with a total of 14 blocks. The entire block was sampled on a weekly basis and assessed for final nematode population density (Pf). After the final assessment, Pf under untreated control over increasing sampling intervals exhibited positive quadratic relations, with the model explaining 90% associations, with optimum Pf of 13804 eggs and J2 at six weeks post-application. In contrast, Pf over increasing sampling intervals under phytonematicide and aldicarb exhibited negative quadratic relations, with the model explaining 95 and 92% associations, respectively. The two had minimum Pf at 974 eggs and J2 and 2205 eggs and J2, respectively, each at approximately six weeks. In conclusion, opposite temporal cyclic nematode population growth patterns post-application of nematicidal products and untreated control provided empirically-based evidence of ‘inconsistent results' in nematode management under phytonematicides.

Mixed Cropping System on Diversity and Density of Plant Parasitic Nematodes

&lt;p&gt;The potential of mixed cropping system on the diversity and suppression of nematodes was investigated at two locations in Ghana. The treatments in the study were; sole plantain, sole cassava and plantain+cassava systems replicated five and four times in a randomized complete block design (RCBD) at Kwadaso in the Ashanti and Assin Foso in the Central region of Ghana respectively. Growth parameters (height and girth) and components of yield (No. of suckers/plant, bunch weight/plant, No. of hands/plant, No. of fingers/plant) were studied on plantain in addition to No. of weevils per plant. On cassava, total biomass, tuber number and tuber weight (yield) were analyzed using GenStat software and means were separated with Fisher’s least significance test at a = 0.05. There were no differences in height and girth of plantain at Assin Foso. However, plant height was 25% and girth 13% more under sole plantain system over the mixed cropping system at Kwadaso. The sole plantain system recorded 60% and 75% more suckers than the Plantain-Cassava system at both locations. Mixed and sole cropping systems did not influence the diversity of nematode community but significant differences were observed in the density of the nematode taxa encountered under the two systems. Throughout the investigation at both locations, it was observed that the mixed cropping system recorded significantly (P &amp;lt; 0.05) lower nematode population densities in comparison to sole cropping system. It is therefore true that an agro-ecological strategy for pests and diseases control is the growing of a mixture of crops differing in their susceptibility to pests and pathogens&lt;/p&gt;

A preliminary survey of plant parasitic nematodes on carrots in Hai Duong province, Vietnam

Hai Duong province is the largest specialized area on the carrot production in Northern Vietnam. Recently, some papers reported about symptom of plant parasitic nematodes appeared in carrot cultivated areas, that causes damage to carrot production. i.e. both quantity and quality are decreased. Based on results of the survey carried out in 2015 at two carrot planted areas, viz. Cam Giang and Nam Sach, Hai Duong province, 17 plant parasitic nematode species of 11 genera, 8 families and 3 orders of the parasitic nematodes, such as Tylenchida, Dorylaimida and Triplonchida were recorded. There are some differences on the specific composition as well as parasitic density of plant parasitic nematodes betweent carrot in Hai Duong and Lam Dong province. However, in both areas there are four parasitic groups appearred, viz. root-knot nematodes, lesion nematodes, root ectoparasitic nematodes and virrus vector nematodes. The presence of root-knot nematodes, lesion nematodes is related to damaged symptom in carot, such as multiple branched root, fork deformities (55.56%), root-knot (33.33%) and shorted root (5.56%).

The Impact of Organic Soil Amendments on Population Densities of Plant Parasitic Nematodes and Okra Yield

The Impact of Organic Soil Amendments on Population Densities of Plant Parasitic Nematodes and Okra Yield

Soil properties and olive cultivar determine the structure and diversity of plant-parasitic nematode communities infesting olive orchards soils in southern Spain.

This work has studied for the first time the structure and diversity of plant-parasitic nematodes (PPNs) infesting olive orchard soils in a wide-region in Spain that included 92 locations. It aims at determining which agronomical or environmental factors associated to the olive orchards are the main drivers of the PPNs community structure and diversity. Classical morphological and morphometric identification methods were used to determine the frequency and densities of PPNs. Thirteen families, 34 genera and 77 species of PPNs were identified. The highest diversity was found in Helicotylenchus genus, with six species previously reported in Spain and with H. oleae being a first report. Neodolichorhynchus microphasmis and Diptenchus sp., Diphtherophora sp., and Discotylenchus sp., usually considered fungal feeders, were also reported for the first time associated to olive rhizosphere. PPNs abundance ranged from 66 to 16,288 individuals/500-cm3 of soil with Helicotylenchus digonicus being the most prevalent species, followed by Filenchus sp., Merlinius brevidens and Xiphinema pachtaicum. Nematode abundance and diversity indexes were influenced by olive cultivar, and orchard and soil management practices; while olive variety and soil texture were the main factors driving PPN community composition. Soil physicochemical properties and climatic characteristics most strongly associated to the PPN community composition included pH, sand content and exchangeable K, and maximum and minimum average temperature of the sampled locations. Our data suggests that there is a high diversity of PPNs associated to olive in Southern Spain that can exert different damage to olive roots depending on the olive variety and their abundance. Further analysis to determine the resistance levels of most common olive varieties to the prevalent PPNs in Spain will help to choose the most appropriate ones for the establishment of new plantations. This choice will take into consideration the specific soils and environments where those olive varieties will be established.

A novel nematode diagnostic method using the direct quantification of major plant-parasitic nematodes in soil by real-time PCR

We have developed a direct quantification method using real-time PCR for various plant-parasitic nematodes. Firstly, specific primers were designed for the root-knot nematode Meloidogyne incognita, the root-lesion nematode Pratylenchus penetrans, the potato cyst nematode Globodera rostochiensis and the soybean cyst nematode Heterodera glycines. A DNA extraction method was then developed beginning with 20 g of soil, a relatively large amount of soil but a necessary amount in the consideration of heterogeneous distribution of nematodes in soil. To estimate the density of the target nematode in soil, calibration curves for each plant-parasitic nematode were obtained by inoculating different numbers of the target nematode and then extracting DNA from the soils. The detection limit was 4-5 nematodes (20 g soil)−1. This method was applied to nematode diagnostics. Soil sampling was done when transplanting of radish and sweet potato in fields was taking place, and the density of plant-parasitic nematodes was measured using both the Baermann funnel extraction method and real-time PCR methods. In some soils, P. penetrans and M. incognita were not found with the Baermann method but were detected with the real-time PCR method. At harvest, damage to crops was evaluated and its relationship with initial densities was investigated. The real-time PCR method more precisely predicted damage to radish and sweet potato by nematodes and was considered to be a powerful tool in the diagnosis of nematode diseases.

Spatial variation in biodiversity and trophic structure of soil nematode communities in a subtropical savanna parkland: Responses to woody plant encroachment

Woody plant encroachment into grasslands generally increases spatial heterogeneity of soil properties and processes and creates “islands of fertility” beneath woody canopies. However, little is known regarding the potential for these changes to influence spatial variation in soil fauna. We quantified population sizes, biodiversity, and trophic structure of soil nematode communities in a savanna parkland where woody plant clusters developed in grassland during the past century. Total nematode density was constant across transects from centers of woody clusters into grasslands. Family richness and Simpson's Dominance Index indicated nematode communities in grasslands and grassland/cluster edges were significantly more diverse than positions within the woody clusters. Relative densities of all nematode trophic groups changed significantly along the transect. Bacterivores nearly doubled in relative density from grassland (35%) to cluster centers (60%), apparently in response to higher concentrations of soil microbial biomass in wooded areas. Relative densities of plant parasitic nematodes decreased along transects from grasslands (35%) to centers of woody clusters (10%), implying decreased nematode herbivory in woody clusters despite much higher root biomass there. The structure index indicated nematode communities within woody clusters were more simplified than those in grassland and edge communities due to reductions in densities of omnivores and predators. Although nematode densities were lower at 10–20 than 0–10 cm, nematode community characteristics were generally similar between soil depths. Changes in nematode community and trophic structure described here could influence biogeochemical processes, species interactions, and successional processes in regions where woody plants are encroaching into grasslands.

An integrated system of summer solarization and fallow tillage for Cyperus esculentus and nematode management in the southeastern coastal plain

Solarization is a form of pest control using clear plastic mulch that allows sunlight to heat the soil to temperatures lethal to plant pests. Fallow tillage is a proven practice to reduce baseline weed densities. Field trials were conducted at the Coastal Plain Experiment Station Ponder Farm from 2003 to 2006 to evaluate integrated systems of pest control using solarization and fallow tillage. Treatments included all possible combinations of four solarization regimes and three fallow tillage regimes. Solarization regimes began in either May, July, September, and included a non-solarized control. Plots were solarized using clear-colorless polyethylene mulch. Frequencies of fallow tillage were weekly and monthly using a power-tiller, and included a non-tilled control. All solarization materials were removed in early October each year and turnip green were direct seeded into the pre-existing plots. The following spring, sweet corn were seeded into pre-existing plots a second time. Solarization beginning in May or July provided excellent control of Cyperus esculentus in plots planted to turnip green and reduced densities of plant parasitic nematodes. Fallow tillage throughout the summer with a power-tiller at monthly or weekly intervals were equally effective. C. esculentus in spring planted sweet corn responded similarly. These results show that an integrated system of solarization and fallow tillage can effectively reduce populations of C. esculentus to manageable levels without the use of fumigants or herbicides, provided that the solarization period during the summer lasts at least 90 days.

Host status of six major weeds to Meloidogyne chitwoodi and Pratylenchus penetrans, including a preliminary field survey concerning other weeds

Abstract A glasshouse experiment was carried out to investigate the host status of six important weeds in intensive agricultural cropping systems to Meloidogyne chitwoodi and Pratylenchus penetrans. Senecio vulgaris L., Capsella bursa-pastoris (L.) Medic. and Solanum nigrum L. were hosts of M. chitwoodi with reproduction factors of 2.5, 2.6 and 7.8, respectively. Echinochloa crusgalli (L.) Beauv. and Stellaria media (L.) Vill. were non-hosts for M. chitwoodi as no galls or eggs were observed. Galinsoga parviflora Cav. is considered a poor host with one out of eight plants producing an egg mass, but maintaining significantly higher population densities in the soil than were recorded in the fallow pots. Echinochloa crusgalli, S. nigrum and S. vulgaris were hosts of P. penetrans with multiplication factors of 1.6, 1.82 and 4.29, respectively. The multiplication rate of P. penetrans on S. vulgaris was similar to the one recorded on maize, the susceptible control. Galinsoga parviflora, S. media and C. bursa-pastoris were non-hosts as no specimen of the target nematode was found in the roots. After 16 weeks, only 1.22 and 0.08% of the original population was still alive for P. penetrans and M. chitwoodi, respectively. In conjunction with the pot experiment, a field survey was conducted at two sites, each of which was known to be highly infested with either M. chitwoodi or P. penetrans. Based on the survey results, Cirsium arvense Scop. and C. bursa-pastoris can also be considered to be hosts of M. chitwoodi, whilst Cirsium arvense, Chenopodium album L. and Polygonum convolvulus L. were recorded as hosts of P. penetrans. These results call attention to the possibility of weeds acting as carriers and point sources of possible high population densities of plant-parasitic nematodes. It emphasises the importance of adequate weed control in an integrated programme for management of M. chitwoodi and P. penetrans and the possible failure of the successful use of non-host crops and fallow in crop rotations when weed control is inadequate.

Assessment of the importance of individual plant-parasitic nematode species in a community dominated by Heterodera sacchari on upland rice in Côte d'Ivoire

AbstractIn temperate climates, densities of plant-parasitic nematodes at or shortly before sowing are a useful predictor of their damage potential. Re-examination of data from nematode communities on upland rice in Côte d'Ivoire showed that interpretation of nematode pest potentials and the damage caused by either individual species, or by the community as a whole, is less simple. The numerical proportion of individual nematode species within a plant-parasitic nematode community, comprising Heterodera sacchari, Pratylenchus zeae , Meloidogyne incognita, Helicotylenchus dihystera, Mesocriconema tescorum and Xiphinema spp., changed with duration of the cropping cycle. The relative importance to the crop of the different species changed with time, and with development of the community structure over the course of the season. Analysis suggested that for H.sacchari, the mid-season population densities were most highly correlated with crop damage (yield loss) and therefore its damage potential for that particular season. The pest potential of other known rice pest species, such as M. incognita and P.zeae, was likely indicated earlier in the season, but the population increase of other nematode species in the community, particularly H. sacchari, compounded the interpretation of the data for other species. The use of single linear regression to assess the importance of individual nematode species conflicted with results of analyses using multiple stepwise regression, while use of cluster analysis permitted the identification of species groups at early and late stages in the cropping season.

Effect of Tillage and Water Management on the Population Behaviour of Root-Knot Nematodes Meloidogyne Triticoryzae in Rice Crop

The effects of puddling and water regimes on hydraulic conductivity (cm/day) of soil and on bulk density (mg/m 3 ) during rice culture, soil physical characteristics of the experimental field population densities of plant-parasitic nematodes have been studied. Puddling reduced the bulk density of soil and decreased the hydraulic conductivity in the upper layers but not in the deeper layers of soil aeration was reduced due to high moisture levels retained in the puddled soil. Population density of M. triticoryzae declined in puddled soil. The invasion of the roots by the second-generation infective juveniles was reduced. The population density of the root-knot nematodes was higher in the non-puddled soil especially in unsubmerged condition compared to puddled and submerged soil. However, if the seedlings were already infected before transplanting and submergence, the nematode could survive well and reproduce within the aerenchyma of the root.