Some Plant Parasitic Nematodes of Fruit Trees in Northern Khorasan Province, Iran

Introduction: Nematodes (Phylum Nematoda) are considered as one of the most abundant and diverse animals on earth. They are found in terrestrial, freshwater, brackish, and marine environments and play important ecological roles in soil ecosystems. The order Tylenchida includes the largest and economically most important group of plant-parasitic nematodes so they have always received ample taxonomic attention. Many plant parasitic nematode species are important pests of fruit trees. They damage the plant by directly attacking roots and subsequently predisposing them to secondary infections by bacteria, fungi by causing replant and pre-plant problems of orchards and also by transmission of viruses. Plant parasitic nematodes feed on a plant root system, ability to take up water and minerals and to transport nutrients to the shoot. This restricts root growth reduce plant vitality and inhibits shoot growth, the combination of which results in decreased in quality and yield. The economically most important species belong to the genera Meloidogyne, Pratylenchus, criconemella, Logidorus, Xiphinema, Trichodorus and Paratrichodorus and are widely distributed in fruit orchards throughout the world. Nematode species are classically defined on the basis of these qualitative and quantitative characters. Although morphological information might help species diagnostics, these characters are homoplasious features in many cases and do not adequately consider the possibility of convergent evolution. As a result, new species descriptions are increasingly supported by molecular evidence. However, the study of morphology remains a critical necessity as morphology is the primary interface of an organism with its environment with key implications for development and ecology. Therefore, a more robust phylogeny based on a combination of morphological and molecular approaches is needed to clarify important relationships within Tylenchomorpha. The purpose of the present investigation was the identification of plant-parasitic nematodes of fruit trees based on morphological and morphometrical characters in Northern Khorasan province. Materials and Methods: In order to investigate the biodiversity of plant parasitic nematodes of fruit cultivation in Northern Khorasan Province, 70 soil samples were collected during 2011-2012. Nematodes were extracted by centrifugal flotation technique and transferred to glycerin according to the modified De Grisse method (1969). The permanent slides were prepared from the extracted nematodes. The nematodes were identified by light microscopy, based on morphological and morphometrical characters. Measurements and drawings were performed using a drawing tube attached to an Olympus BH2 light microscope. The ratios and the morphometric symbols used in morphometric tables of each specimen. Nematodes were identified based on morphological and morphometrical characters using identification keys. Results and Discussion: In this study, 17 species from 13 genera belonged to sub order Tylenchina were identified as follows: Aphelenchoides richardsoni, Aphelenchus avenae, Basiria graminophila, Boleodorus thylactus, Ditylenchus filimus, D. medicaginis, Filenchus cylindricaudatus, F. thornei, Geocenamus tenuidens, Helicotylenchus digonicus, H. pseudorobustus, Heterodera schachtii, Merlinius brevidens, Pratylenchus neglectus, P. thornei, Tylenchorhynchus latus, Zygotylenchus guevarai. Among these species, Pratylenchus neglectus, Merlinius brevidens and Boleodorus thylactus were more frequent, respectively. Ditylenchus filimus is reported for the first time from Iran. D. filimus is characterized by low and striated head, stylet 7-9 µm, median bulb muscular, glandular bulb offset, posterior vulva( V=81-85), PUS=0.5-1.1, tail conical with very sharp and pointed terminus. Conclusion: In this study, 17 species from 13 genera belong to suborder Tylenchina were identified. Among these species, Pratylenchus neglectus, Merlinius brevidens and Boleodorus thylactus had the most frequency respectively. Ditylenchus filimus is reported for the first time from Iran

Identification of Aphelenchoides Fischer, 1849 Species (Nematoda: Aphelenchoididae) Collected from Rapeseed Fields in North Khorasan Province

Introduction: Rapeseed is seeded in the fall, from late september through late october. Seed should be broadcast across the garden. Plants are left to grow through the winter and tilled into the soil in march. Rapeseed crops have a high sulfur requirement, a nutrient that is commonly deficient in sandy soils. When growing rapeseed for nematode control, be sure to take a sample of your soil to your local cooperative extension office for testing to find out if you need to add additional sulfur. If sulfur levels are too low, the rapeseed crop will not be able to generate the organic compounds that suppress nematode populations. Brassica and mustard cover crops are known for their rapid fall growth, great biomass production and nutrient scavenging ability. Brassica napus is the most important oil plant in the world. They must be planted earlier than winter cereal cover crops in most regions. There are many species of plant parasitic nematodes in the farms. High population densities of them cause economically significant crop reductions in most agricultural crops including Brassica napus production. The life cycles of different nematode species vary, and may include feeding on the outside of the roots or penetration and development within the roots. Nematodes survive between susceptible crops by feeding on other crops and weeds, and are spread in contaminated soil on machinery, windblown soil, and infested seed pieces. The different genera of plant parasitic nematodes such as Heterodera, Meloidogyne and Pratylenchus were recorded from Brassica fields in the world. Root-knot nematodes cause the round to spindle-shaped galls on the roots. Aboveground e-shaped galls on the roots. Aboveground symptoms of nematode injury appear as patches of stunted or dying plants. Infected plants may wilt when stressed by high temperature or moisture extremes. Pratylenchus spp. is a microscopic worm-like organisms less than one-millimetre in length, which feed on root tissues. All species of root lesion nematode have a wide host range. The root cortex (or outer root layer) is damaged and may disintegrate. Diagnosis is difficult and can only be confirmed with laboratory testing, particularly to identify the species as all RLN species cause identical, symptoms. The objective of this study was to investigate the plant parasitic nematodes associated with Rapeseed fields in North Khorasan province of Iran. Materials and Methods: In order to identify the plant parasitic nematode fauna of Rapeseed fields in the North Khorasan province, 40 soils and root samples were collected during the years 2007-2008. From each field several small samples were taken from all areas of the field. Then the soil samples were put in a polyethylene bag with pertinent information about each sample and then brought to the laboratory and kept in the refrigerator at about 4ºC, until they were processed for nematode extraction and other activities. Nematodes were extracted using the centrifugal flotation technique and transferred to glycerine according to the modified Sein-Horst method (1959). The permanent slides were prepared from the extracted nematodes. The nematodes were observed by light microscopy and identified based on morphological and morphometrical characters. Results and Discussion: In this study, five species of the genus Aphelenchoides namely: A. limberi, A. daubichaensis, A. delhiensis, A. confusus, A. rutgersi were identified. While the last four species are reported for the first time in Iran. A. daubichaensis is characterized by having cuticular papillae (mucron) tail end of the taper and the central part is sharp. A. delhiensisis characterized in having three lateral field in the body and the mucron centrally located on the tail. A. confusus characterized in having a stylet without end nodes, oval, large, offset spermatecha and full of sperm and the tail cone at the end of the round and without mucron. A. rutgersi, is characterized by having three lateral fields in body, stylet with small basal swellings, oval spermatecha and full of sperm and post-vulval sac short, usually one and a half vulval body- widths. Conclusion: In this study, many species from different genera of plant parasitic nematodes belonging to suborder Tylenchina were identified. From genus Aphelenchoides, 5 species were identified, such as A. limberi, A. daubichaensis, A. delhiensis, A. confusus, A. rutgersi. Among these species, the four species A. daubichaensis, A. delhiensis, A. confusus, A. rutgersi are reported for the first time in Iran

Identification of Plant-parasitic Nematodes in Cotton Fields in Southern Khorasan Province

Introduction: Gossypium species are distributed in the arid to semiarid regions of the tropical and subtropical, generally shrubs or shrub-like plants. The leaves are broad and lobed with three to five lobes. The seeds are contained in a capsule called a "boll", each seed surrounded by fibers. Commercial species of cotton plant are Gossypium hirsutum (>90% of world production), G. barbadense (3-4%), G. arboreum and G. herbaceum (together, 2%). Cotton is grown as a cash crop; it is often grown in a monoculture system that favors the development of a nematode community dominated by one or a few parasitic species. The different genera of plant parasitic nematodes such as Haplolaimus, Helicotylenchus, Blanolaimus, Pratylenchus, Paratrichodorus, Meloidogyne, Merlinius, Xiphinema, Tylenchorynchus, Rotylenchulus, Scutellonema, Heterodera, Ditylenchus, Longidorus, Aphelenchoides, Aphelenchus were recorded from cotton fields in the world. The objective of this study was to investigate the plant parasitic nematodes associated with cotton fields in Southern Khorasan province of Iran. Materials and Methods: In order to identify the plant parasitic nematodes in cotton fields in Southern Khorasan province, 56 soil samples were collected from different areas during 2013 and 2014. Soil samples were washed and nematodes were extracted by combined sieving and centrifugal-flotation method of Jenkins (1964) and Whitehead tray method (1965). Nematodes were fixed and transferred to glycerin by using the method of De Grisse (1969). The permanent slides were prepared and the nematodes were studied by light microscope. Results and Discussion: In this study, 15 species from 10 genera related to order Tylenchomorpha, were identified as follows: Aphelenchus avenae, Basiria graminophila, Boleodorus clavicaudatus, B. pakistanensis, B. thylactus, Ditylenchus hexaglyphus, D. tenuidens, D. valveus, Geocenamus rugosus, Filenchus vulgaris, Pratylenchus neglectus, P. thornei, Scutylenchus quadrifer, Merlinius brevidens, Zygotylenchus guevarai. One genus of cotton-parasitic nematodes known to cause yield loss were found in this survey (Pratylenchus spp). Other parasitic nematodes not known to cause yield loss also were found. Three species, including Boleodorus pakistanensis, Ditylenchus hexaglyphus, D. valveus are reported as new records for Iran. Boleodorus pakistanensis is characterized by four incisures, head low, unstriated and conoid shape, stylet 8.5-10µm with cone short and slender knobs, non-muscular median bulb, Basal bulb pyriform, posterior vulva (v=68.1-72.4 ; v/=77.5-88.4). Tail elongate-conoid, central arcuate, ending in a finely rounded terminus. B. pakistanensis resembles, B. flexuosus B. teres, B. thylactus and B. cylindricus. B. thylactus but can be differentiated by the more posterior position of the opening of the dorsal gland (2 vs 3-5); B. flexuosus has a more anterior vulva (V=54-63 vs 68.1-72.4); B. teres has a more anterior vulva (V=54-63 vs 68.1-72.4), tail shape and stylet length (10-12 vs 8.5-10); B. cylindricus has a more anterior position of the opening of the dorsal gland (7 vs 3-5) and more tail (88-101 vs 72-88.5). Ditylenchus hexaglyphus is characterized by six lines in lateral fields, low head, stylet 8-9µm with cone shorter than the shaft and small elongated knobs, non-muscular median bulb, Posterior bulb offset, posterior vulva (v=82.3 -83.5; v/=87.8-89.6). Tail ventrally curved, terminus rounded. Having non-muscular median bulb, six incisures, short stylet and posterior vulva. D. hexaglyphus resembles D .medians, D. taylori, D. affinis, and D. tuberosus. However, none of these species have such small stylet knobs, and all but D. affinis have longer PUS than that observed in D. hexaglyphus. D. taylori more anterior vulva (V=75-77 vs 82.3-83.5) and tail appears to be thinner (c/=6-7 vs 2.9-3.8); D. affinis has a more anterior vulva (V=76-80 vs 82.3-83.5). Ditylenchus valveus is characterized by six incisures, annulated head, stylet 8-9µm with short cone and small rounded knobs, muscular median bulb with small. Posterior bulb offset, posterior vulva (v=74.3 -81.5; v/=84.9-89.2). Tail terminus rounded. Because of six incisures, short stylet, vulva position, oesophagus structure and tail shape, D. valveus resembles D. acutatus D. myceliophagus and D. medicaginis. D. myceliophagus differs from D.valveus by tail shape and generally overlapping oesophagus; D. medicaginis differs from D. valveus mainly by tail shape and also slightly more posterior vulva position (78-83 vs 74.3-81.5); D. acutatus differs from D. valveus mainly by tail shape. Conclusion: In this study, 15 species from 10 genera of plant parasitic nematodes were identified. Among these genera and species, three species including Boleodorus pakistanensis, Ditylenchus hexaglyphus, D. valveus are reported as new records for Iran