Commercial Biological Control Agents Targeted Against Plant-Parasitic Root-knot Nematodes

831 Vol.57, n.6: pp. 831-841, November-December 2014 http://dx.doi.org/10.1590/S1516-8913201402540 ISSN 1516-8913 Printed in Brazil BRAZILIAN ARCHIVES OF BIOLOGY AND TECHNOLOGY A N I N T E R N A T I O N A L J O U R N A L Commercial Biological Control Agents Targeted Against Plant-Parasitic Root-knot Nematodes Marie-Stéphane Tranier1*, Johan Pognant-Gros1, Reynaldo De la Cruz Quiroz2, Cristóbal Noé Aguilar González2, Thierry Mateille3 and Sevastianos Roussos1 1 Institut Méditerranéen de Biodiversité et d'Ecologie marine et continentale (IMBE); UMR CNRS IRD; Aix Marseille Université; Marseille - France. 2Departamento de Investigación en Alimentos; Universidad Autónoma de Coahuila; Saltillo - México. 3Centre de Biologie pour la Gestion des Populations (CBGP); IRD; Montferrier sur Lez Cedex - France ABSTRACT Root-knot nematodes are microscopic round worms, which cause severe agricultural losses. Their attacks affect the productivity by reducing the amount and the caliber of the fruits. Chemical control is widely used, but biological control appears to be a better solution, mainly using microorganisms to reduce the quantity of pests infecting crops. Biological control is developing gradually, and with time, more products are being marketed worldwide. They can be formulated with bacteria, viruses or with filamentous fungi, which can destroy and feed on phytoparasitic nematodes. To be used by the farmers, biopesticides must be legalized by the states, which has led to the establishment of a legal framework for their use, devised by various governmental organizations. Key words: Biopesticides, Meloidogyne spp., Filamentous Fungi, Homologation, Production, Formulation INTRODUCTION Root-knot nematodes are disease-causative agents, well-known by farmers, for example, tomato producers in Morocco. Each year, these microscopic worms cause considerable losses. Biopesticides may be a good solution to reduce the damages, but they have to be legalized by the governments. Filamentous fungi may play a good role in the control of this pest, using different action pathways. They have to be formulated to preserve their viability and virulence against the nematodes, and then to be approved for use on the crops by farmers. ROOT-KNOT NEMATODES (RKN) Nematodes are classified under the Nematoda Phylum, which forms part of the Ecdysozoa superphylum, from the Greek ecdysis (moulting) * and zoo (animal). They possess a cuticle and must moult to continue their development (Bélair 2005). Most of them are said “free” and feed essentially on bacteria, fungi, protozoa and other nematodes, and only a minority parasites animals and plants (Bélair 2005). Meloidogyne spp. or RKN are round worms (Brand et al. 2009) belonging to Tylenchida family. They are cylindrical and thread-like triploblastic Metazoans that show bilateral symmetry, a thick cuticle, and non-ciliated, nonsegmented teguments (Grassé et al. 1965). They were discovered during the 14th century as phytoparasites of intertropical and warm climate cultures. The agricultural losses they cause, in particular in greenhouse cultures of tomatoes in the Souss-Maasra Drâa region in Morocco, are considerable. Worldwide, more than USD 125 billions/year are lost due to nematodes, most of Author for correspondence: Braz. Arch. Biol. Technol. v.57 n.6: pp. 831-841, Nov/Dec 2014 832 Tranier, M-S. et al. them due to RKN (Koenning et al. 1999; Chitwood 2003; Collange et al. 2011; Bissadou et al. 2012). The degree of these damages can be even more severe as nematodes can increase susceptibility to other parasites (Bridge et al. 2005). The Meloidogyne genus subdivides in different species, all phytophagous, with M. arenaria, M. incognita, M. hapla and M. javanica being commonly widespread (Netscher 1970; Sawadogo et al. 2000; Hunt and Handoo 2009). The number of plants susceptible to Meloidogyne spp. is very high (more than 2,000 species, a constantly increasing figure), and includes tobacco (Nicotiana tabacum), coffee (Coffea arabica), tomato (Solanum lycopersicum), Niebe (Vigna sinensis), Kenaf (Hibiscus cannabinus L.), sugar cane (Saccharum officinarum), tea (Camellia sinensi), carrot (Daucus carota), melon (Cucumis melo), etc. Meloidogyne spp are round worms, 0.4 to 1.0 mm long and 0.25-0.75 µm in diameter for the females and 1.2-1.5 mm long and 30-36 µm in diameter for the males (Agrios 1997). These present a stylet, which is used to pierce the cell walls of the roots of the host plants (Davis et al. 2000). As they enter the root, the larvae will provoke a cortical cell hypertrophy due to the excretion of secretions through the stylet. Multinucleated “giant cells” are thereby formed (Bird 1962), which cause the formation of gall, which is characteristic of the attack by a Meloidogyne spp. Once hatched, J2 free larvae become obligatory parasites that have to continue their cycle into adult stage in host-plant roots only (Sharon et al. 2001). For that purpose, they swim into the water pellicle surrounding the soil particles. Once they penetrate the root thanks to the stylet, the larvae move both in and between the cells. They move to the central cylinder along which they immobilize (Fig. 1A). At this time, L3 and L4 larvae turn into sexual adults, presenting strong dimorphism (Fig. 1B): males stay vermiform whereas females become pyriform and sedentary, their heads lodged in giant cells. Once fecundated, females lay eggs (around 500/mass) agglomerated at all the stages of development in a gelatinous substance, from the unicellular stage to the ready-to-hatch stage. Egg development between these two stages could take from seven to nine days at 28°C. During this time, nematodes undergo a first molting and the larvae that hatch are J2 secondstage larvae (De Guiran and Netscher 1970). A higher temperature may accelerate the cycle; yet temperatures above 40°C are lethal. Eggs are the nematodes’ resistant form, so they survive unfavorable conditions of life. In the absence of males, females are also able to produce fertile eggs in a parthenogenetic way (Agrios 1997). Typical symptoms of damage caused by the nematodes are a reduction of the root system, root structure distortion or root diameter increase, and gall presence. Plants turn yellow and wither and a production decrease is observed (Agrios 1997). B A C Figure 1 - A. Schematized cycle of Meloidogyne spp. - 1. Free second stage larva; 2. Second stage larva penetrating a growing root; 3. Root in formation : a-b : Swolled second stage larva ; c : Giant cells ; 4. Gall containing : a : adult female which had laid her eggs in the gelatinous substance ; b : adult male curled up in the larval envelopes ; c : Giant cells; 5. Free adult male (By De Guiran G. and Netscher C. 1970) ; B. Photo of females of M. javanica (M. Tranier) and C. J2 larvae of M. javanica (M. Tranier). Braz. Arch. Biol. Technol. v.57 n.6: pp. 831-841, Nov/Dec 2014 Commercial Biopesticides against Plant Parasitic Nematodes (...truncated)