نوع مقاله : مقالات پژوهشی
1 دانشگاخ فردوسی مشهد
2 دانشگاه فردوسی مشهد
عنوان مقاله [English]
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.
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