In order to identify the plant parasitic NEMATODES (Tylenchida) of the RICE fields in Guilan province, about 75 soil and root samples were collected from different fields during 1995 and 1996. The samples were washed and the NEMATODES were extracted by centrifugal suger-floating method. The NEMATODES were fixed and transfered to glycerin by modified seinhorst method (De Grisse, 1969). Then the permanent slides were prepared from NEMATODES including cone-top of cysts and some cross sections of some NEMATODES. The specimens were studied by light microscope.Cysts were also, prepared for scanning electron microscope (SEM) based on HIRSCHMANN and TRIANTAPHYLLOU's method (1979). Ten known plant parasitic NEMATODES belonging to 8 genera were identified including Aphelenchoides besseyi,A. bicaudatus ,Basiria graminophila, Criconemella paragoodeyi, Filenchus facultativus, F. polyhypnus, Helichotylenchus crenacaudatus, H. digitiformis, Heterodera oryzae and Tylenchorhynchus annulatus. F. polyhypnus, H. digitiformis and H. oryzae are new for nematode fauna of Iran as described in the text. In this study the morphological and morphometrical characters of these three species as well as H. digitifomis are described.

Today, global warming is one of the most important human concerns in the fields of economy, energy and environment. The most important element in global warming is the burning fossil fuels that release the greenhouse gases including CO2. The researches by the Intergovernmental Panel on Climate Change show that global warming will rise more than 2 degrees centigrade by the end of the century with respect to the pre-industrial era, if no effort is made to reduce CO2 emissions. Since the MENA region is one of the most vulnerable regions in the world due to climate change, so the main purpose of this study is to assess the effects of climate change on the economic variables in MENA region until 2105. For this purpose RICE model is used which is based on the computational general equilibrium model. The results indicate that the global average temperature will rise to 4. 49 degrees centigrade until 2105 year in comparison to the pre-industrial era, if no policy is implemented to prevent rising temperatures. The trend of regional GDP and consumption are similar and will increasingly move. In the long-run, the capital accumulation will increase in the upper-middle income, the lower-middle income and the high income countries, respectively,while employment will increase in the lower-middle income, the upper-middle income and the high income countries, respectively. Environmental damage is the most in the high income countries in comparison to the other groups in MENA region.

Identifying the constraining factors of production and yield gap is very important. Therefore; this research was performed to identify the production constraining factors of local RICE cultivars. All management practices from nursery preparation to harvesting stages for 100 paddy fields of local RICE cultivars were recorded through field studies, in Sari, from 2015-2016. In the CPA, the actual and calculated potential yield were 4495 and 5703 kg/ha, respectively and the gap was 1221 kg/ha. The yield gap caused by number of top-dressing variables was 324 kg/ha, equal to 27% of the total yield gap. The yield gap related to previous year of legumes cultivation was 218 kg ha-1, equal to 18% of the total yield variation. Among the 10 variables entered in the CPA model, the effects of top-dress fertilizer application and its application frequency and foliar application were remarkable, which could compensate a significant part of the yield gap (444 kg/ha, 37% of total) in the farmers’ fields by managing these variables. According to boundary line analysis (BLA) finding, actual yield mean on the basis of optimal limit related to 12 variables under study was 5369 kg/ha, with 881 kg/ha yield gap . Mean relative yield and relative yield gap for 12 variables (transplanting date, seedling age, number of seedlings per hill, planting density, nitrogen and phosphorous per hectare, nitrogen before transplanting, harvesting date, lodging problem, pest problem, diseases problem and weeds problem) were 83.64 and 16.35 kg/ha, respectively. Based on the finding, it can be stated that the model precision is appropriate and can be applied for both estimation of the quantity of yield gap and determining the portion of each restricting yield variables.

In order to evaluate the performance of the CERES-RICE model in RICE biomass and grain yield estimation in large scale, this study was carried out in paddy fields of Guilan, Iran. First the model was calibrated and evaluated using data from a research at RICE Research Institute of Iran, then the model accuracy was assessed in 26000 ha of Some Sara region.110 common farmers fields were chosen, the soil, water, crop samples and other needed information were taken. The model was ran for each field. The results showed that the Error of yield and biomass estimation in research station were below 10 percent. The results in large scale showed that the model estimation of yield and biomass could be categorized in three different parts. While in fields with average biomass and yield observation the setimation error was negligible. Underestimation was observed in the fields with the yield above the average of the region while in high yielding fields overestimation was observed. The Normalized Root Mean Square Error was about 22.7 and 21% for biomass and yield prediction. Although in some cases the error was about 50%, in 75% of the region it was in range of 0-10%, and in 95 % of the region it was in range of 0-20%. Water productivity based on water used in most of the fields was in the range of 0.5-0.6 kg/m3 and the water productivity based on transpiration was 0.85-0.9 kg/ m3. The model showed a satisfactory accuracy to estimate both yield and biomass in large scale paddy fields.

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.

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.

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.