Role of Nematode-Trapping Fungi for Crop Improvement under Adverse Conditions
Phytonematodes cause significant economic loss to a wide variety of crops by inducing biotic stress to the plant. They cause dramatic changes in the morphology and physiology of the host root system. The damage is difficult to recognize at first sight bec
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Role of Nematode-Trapping Fungi for Crop Improvement under Adverse Conditions Rakesh Kumar Singh, Dipesh Kumar Trivedi and Amit Srivastava
1 Introduction Nematodes are small round worms mostly found in all the natural habitats (soil, aquatic and marine). A large number of nematodes are saprophytic free living and feed on decaying plant and animal matter and sustain themselves by consuming bacteria or other microscopic organisms. Some other nematodes are phytonematodes which are plant parasitic, attacking mainly the roots of the plants. More than 20 phytonematode species acting as obligate parasites of higher plants, have been recorded and majority of them belong to the order Tylenchida. Phytonematodes that cause biotic stresses are migratory ectoparasites, migratory endoparasites, semiendoparasites and sedentary endoparasites. These sedentary endoparasitic nematodes are characterized by their ability to produce specialized organs as feeding cells within plant tissues, which mainly suppresses photosynthesis and process of respiration in plant tissues (Schans 1991). These parasitic nematodes possess certain structural characteristics which ensure their existence in plant tissues. These include the stylet adopted for penetration of plant cell walls and esophageal glands and phasmids which discharge some enzymatic secretions into the root tissues that help in the establishment of pathogenesis of nematode-induced plant diseases. Phytonematodes create stress factors, to which plants respond in more or less the same way as abiotic stress. The biotic stress induced by parasitic nematodes have several characteristics distinguishing it from stress reactions caused by other pathogens. R. K. Singh () Department of Mycology & Plant Pathology, Institute of Agricultural Sciences, Banaras Hindu University, Varanasi, UP, India e-mail: [email protected] D. K. Trivedi Plant Molecular Biology, International Centre for Genetic Engineering and Biotechnology (ICGEB), New Delhi, India A. Srivastava School of Biotechnology, Faculty of Science, Banaras Hindu University, Varanasi, UP, India N. Tuteja, S. S. Gill (eds.), Crop Improvement Under Adverse Conditions, DOI 10.1007/978-1-4614-4633-0_12, © Springer Science+Business Media New York 2013
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These differences are mainly due to the high level of development of the trophic, reproductive, excretory and response of nervous systems in phytonematodes. Compared to other phytopathogens, plant nematodes exhibit a higher degree of motility and have a more sensitive sensory system to make them safe from foreign invasion (Zinov’eva et al. 2004). In general, the most widespread and economically-important phytonematodes are root knot and cyst nematodes. These phytonematodes cause heavy losses in some economically-important crops viz., 18–25 % loss in vegetables, 20–25 % in pulses and 18–23 % in oil seed crops. Global annual yield loss of major crops by nematodes damage is estimated to be 12.3 % (Sasser 1989), causing annual losses of nearly $ 100 billion worldwi
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