Phytochemicals of some plants are suppressive to the ROOT-KNOT NEMATODES (Meloidogyne spp. ). In this study, effects of aqueous extract or dry powder of several plants on the activity of M. incognita and M. javanica were investigated. Treatment of second stage juveniles (J2s) of the NEMATODES with aquatic extracts of 25 plant species under laboratory conditions showed that after 48 hours, extracts of eruca, ornamental chili pepper, tarragon, caster bean, sesame, thistle, chinaberry and dyer's croton caused more than 50% mortality of the J2s of both NEMATODES. In pasteurized soil, extracts of scarlet sage and safflower seed with 78. 9% and 46. 9% reduction of reproduction factors (RFs) of M. incognita and M. javanica, respectively, were the most effective plants in treatment of tomato plants (cv. Early Urbana) with 13 different plant extracts. In addition, eruca and creeping thistle extracts reduced RFs of both species. None of the treatments affected fresh and dry shoot weight of tomato. In field soil, extracts of eruca and caster bean with 57. 2% and 51. 0% reduction of RFs of M. incognita and M. javanica in tomato plants, respectively, were the most effective extracts among eruca, caster bean, tarragon and creeping thistle plants. All treatments significantly increased the fresh shoot weight of infected tomato. In pasteurized soil, scarlet sage powder with 70. 3% and creeping thistle with 49. 7% had the highest effect on RF reduction of M. incognita as compared to ornamental chili pepper, castor bean, chinaberry and safflower seed.

Root knot NEMATODES (Meloidogyne spp.) ranked among the top five major plant pathogens because of their world wide distribution, extensive host ranges and involvement with fungi and bacteria in disease complexes. The previous studies on the host ranges of Meloidogyne species, on some of the medicinal plants indicated that the plants such as plantain, hemp, parsley, ash, spearmint and coriander are the hosts of several species of rootknot NEMATODES in Iran and Esfahan province (AKHIANI et al, 1984. Iran. J. Plant Path 20) In order to determine the specific hosts of each species on medicinal plants ,130 soil and root samples were collected from the various research stations in Esfahan, including, Dastgerd, Najafabab, and Kashan during 1999-2002.

Plant parasitic NEMATODES are amongst the most economically important groups of pathogens. The use of resistant cultivar, crop rotation, chemical control, antagonistic organisms and biocontrol agents are the principal methods for management of the NEMATODES. Natural nematode resistance genes present in gene pools of crop species and their relatives have been used with the aim of transferring such traits into economically important plants where effective resistance is lacking. Biotechnology contributes to this process via marker-assisted selection to identify the best nematode resistance genes, and increasingly in providing new knowledge of target genes, and the potential to exploit this knowledge using transgenic technology. Thus recent advances make it possible to exploit specific aspects of nematode-host plant interactions to design control strategies that include enabling plants to prevent nematode invasion, migration through tissues and reducing feeding ability or nematode fecundity. Application of RNAi, new biotechnology-based chemical nematicides and some other methods are amongst the modern strategies of control. New traits would be added to existing crop genotypes with the best conventional or natural nematode resistance to increase the effectiveness and durability of the nematode resistance trait. Biotech trait expression could also be limited to roots to minimize expression in harvested parts.

The abundance ofNEMATODES in different ecosystems makes thema most desirable agentfor monitoringenvironmental pollution. They are, indeed, considered as the most promising candidates for bioindication of soil disturbances such as heavy metals pollution in the soil. Studies ofthe effects of such heavy metals as lead, cadmium, chromium, copper, nickel, zinc, and selenium on different nematode generain different trophic groups usingdiversityanalysis and nematode assemblage indices have shownconsiderable changes in the populations of certain genera of NEMATODESwith increasing concentration of each specificmetal. Despite theunique characteristics of NEMATODESinmonitoring soil pollution, it is difficult to generalize the effects of toxic metal pollutants on nematode assemblages in soil asthe outcome of such analyseslargely vary with ecosystem, spatial scale, andsuchlocal characteristics as pH, vegetative cover, and the composition of indigenous nematode fauna present in the soil. In the evaluation of nematode community indices, it is, therefore, preferable toremove the genera that lead to ambiguity in predictions and to restrictthe indices only to those belonging to known genera with already establishedsensitivity or response to specific types of disturbance. Thus, population index analyses will not only yield better predictions but will also be more cost-effective. Examples of practical and commercial applications ofnematode assemblage analysis in other countries formonitoring chemical pollution in aquatic habitats are available that can be usefully exploited toward applied researchto overcome the present limitations in using NEMATODES formonitoring soil heavy metal pollution in Iran.

In order to identify thylenchs species (Superfamily Tylenchoidea and suborder Aphelenchina) in Kerman province, 150 soil and root samples were collected from Kerman province during 2004 and 2005. The samples were washed and the NEMATODES extracted by centrifugal floatation technique. They were then fixed and transfered to glycerin according to the De Grisse method (1969). The permanent microscopic slides were prepared from the extracted NEMATODES. Morphological and morphometrical characters of the species were studied by light microscopy. As a resalt, 21 species belonging to several genera Tylenchoidea, three species of Aphelenchides and one species of Stictylus were identified. Among them, Cephalenchus lobus Dhanachand & Jairajpuri, 1980, Coslenchus areolatus (Egunjobi, 1967) Siddiqi, 1978 and Rotylenchus eximius Siddiqi, 1964 are new records for Iran.

During 2000-2002 a study on NEMATODES of 665 fish specimens from Khouzestan province were carried out by set net and electro fishing. Fishes were collected from 3 stations in Hoor- Al- Azim, Hoor- shadegan and Karoon river.There were Aspius vorax (44 specimens), Barbus grypus (75 specimens), B. luteus (175 specimens), B. sharpeyi (94 specimens), B. pectoralis (8 specimens), B. esocinus (9 specimens), Liza abu (130 specimens), Cyprinion macrostomum (14 specimens), Cyprinus carpio (44 specimens) and Silurus triostegus (22 specimens). From 665 fishes 21% were infected by different parasitic worms collected parasites: Rhabdochona denudata, Rh. fortunatowi, Rhabdochona sp., Proleptinae gen. Cucullanus sp., Pseudocapillaria tomentosa, Philometra karunensis, Philometra sp., Anisakis sp.,Contracaecum sp. Rhabdochona fortunatowi is the first report in, B. pectoralis, B. luteus, B. grypus, S. triostegus and Cyprinion macrostomum of Khouzestan province area.

In order to identify the biodiversity of plant parasitic NEMATODES in vegetable fields of Tabriz, during 2004-2005, 88 soil and a few root samples were collected from rhizosphere of 25 dominantly cultivated vegetable crops. NEMATODES were extracted by combined sieving and centrifugal–flotation method and processed to be transferred to glycerin. After preparing microscopic slides, the morphological and morphometrical features of the NEMATODES were studied using the light microscope equipped with a drawing tube. The morphological features and measerments of the extracted NEMATODES were compared with those ones given in literature and similarities and differences with original descriptions and closest species were discussed. As a result, 25 species belonging to 16 genera including Amplimerlinius globigerus, Aphelenchus avenae, Aphelenchoides bicaudatus, A. haguei, A. richardsoni, Boleodorus thylactus, Criconema mutabile, Criconemoides informis, C. mongolensis, Ditylenchus medicaginis, Filenchus vulgaris, Geocenamus brevidens, G. rugosus, Helicotylenchus digonicus, H. exallus, H. pseudorobustus, H. vulgaris, Heterodera cruciferae, Mesocriconema antipolitanum, M. curvatum, Paratylenchus mexicanus, Pratylenchus alleni, P. neglectus, Psilenchus hilarulus and Zygotylenchus guevarai were identified. Most of the NEMATODES are already recoded from Iran and herein, three species namely, Aphelenchoides haguei, Aphelenchoides richardsoni and Pratylenchus alleni and one newly reported species (Helicotylenchus exallus) are described.