نماتدهای انگل گیاهی مزارع لوبیا در استان مرکزی

Introduction
Regarding the importance of bean production in supplying of plant based protein for human being societies and its area under cultivation in Iran, identification and management of pests and diseases associated to this crop are important. Plant parasitic nematodes are one of the biotic agents that adversely affect the production of bean crops. In order to manage these pathogens, their identification and distribution is necessary. Plant parasitic nematodes damaging bean are widely reported through the world. In Florida, Belonolaimus longicaudatus ,Paratrichodorus christei, Dolichodorus heterocephalus and Hoplolaimus spp. are reported from bean cultivated field while causing severe damage (Rhoades, 1964, 1974). In Michigan Pratylenchus penetrans was the most common root lesion nematode. In fact Pratylenchus spp. have wide host ranges and are pathogenic to many important crops viz Phaseolus vulgaris. There are a few reports across Iran regarding the plant parasitic nematodes of bean. In a study of plant parasitic nematodes of pulse crops in southern Balochistan, Pratylenchus neglectus and Meloidogyne javanica were reported from bean fields. Five species Aphelenchoides cyrtus, Ditylenchus medicaginis, Merlinius brevidens, D. parvus and Paratylenchus coronatus with 37.6, 30.8, 24.6, 20.5 and 19.1 percent frequency, respectively, were the most common nematode species in the legume fields of Lorestan province. Although Markazi province is one of the poles of bean-growing in Iran but there is a few information about plant parasitic nematodes on bean. The aim of this study was to identify the plant parasitic nematodes associated with bean, determination their population density and geographical distribution.
 
Materials & Methods
In order to determine the plant parasitic nematodes 174 root and soil samples were collected from bean fields in Khomein, Shazand and Arak cities during 2012-2013. The samples were analyzed and the population density of the extracted nematodes was counted at genus level using counting slide. Then the obtained nematodes were fixed and transferred to hydrated glycerol, the nematodes were mounted on microscopic slides and identified at species level, based on morphometrical and morphological characters. Cyst nematodes were isolated using Fenwick can technique. After analyzing the samples, infested areas were identified and frequency based on the number of species compared to the total sample were determined.
 
Results & Discussion
In this study, 22 species belonging to 18 genera of suborder Tylenchina, infraorder Tylenchomorpha were identified. Ditylenchus destructor, Ditylenchus sp., Aphelenchoides sp. and family of Pratylenchidae including P. neglectus, Zygotylenchus guevarai and Pratylenchoides ritteri from family Merliniidae with 100, 58 and 95 percent frequency respectively, were the most common nematode species in the bean fields of Markazi province. Subfamily of Merliniinae the genera of Merlinius, Scutylenchus, Tylenchorynchus and Amplimerlinius with 56 percent frequency, were found in Khomein and Shazand bean fields. The family of Hoplolaimidae was detected in Khomein and Shazand bean fields with 39 percent frequency. Among the cyst forming nematodes in addition to Heterodera filipjevi which was found in bean fields rotated by wheat, H. goettingianawas found in a bean field in Ghasemabad, Arak, this species in known as pea cyst nematode. H. goettingiana had already been reported from two areas in Dorud region (Lorestan province). This species was found in some wheat fields that bean was one of the crops in rotation. According to the occurrence of this species in bean field in Markazi province which borders Lorestan Province, it seems that it is distributed in pea and bean fields in two provinces. Some nematodes identified in this study are important as plant parasiting and damaging for bean. P. neglectus with 93, 42 and 22 percent frequency respectively detected in the bean fields of Khomein, Arak and Shazand. Root lesion nematodes were reported as the most common nematodes on bean and other legumes in Italy, North africa and Middle East. Elliott & Bird (1985) reported damage of root lesion nematodes in bean fields among 10 to 80 percent.Therefore, it is necessary to research on the importance and evaluation the damage caused by this species. Moreover due to the abundance of Ditylenchus in bean fields of Markazi province, it needs intensive research as far as crop loss aspects are concerned.
 
Conclusion
In the present study, among identified nematodes, family of Pratylenchidae was the most important plant parasitic nematode with 58 percent frequency. Also genus of Ditylenchus spp. detected in all of bean fields of Markazi province.