Discussion and Conclusion

Présentation au sujet: "Discussion and Conclusion"— Transcription de la présentation:

1 Discussion and Conclusion
Study of the persistence of two entomopathogenic bacteria on the vegetation cover of winter soft wheat and soil Hakima Oulebsir-MohandKaci 1, Fahima 0uttar2 et Bahia Doumandji-Mitiche2 (1) Laboratory of valorization and conservation of biological resources, Department of Biology, Faculty of Science, University of M'hamed Bougara, Boumerdes, Algeria (2) Department of Agricultural and Forest Zoology, Ecole National Superior Agronomic, Algiers, Algeria. Abstract: The bacterial strains used in this work were isolated from rhizospheric soil of the date palm in the Algerian Sahara. They are identified as Bacillus sp. (HE799656) and Bacillus sp. (HE805963). In order to study the persistance of bacteria in the foliage, wheat cultivation took place in pots placed under greenhouse and the treatment was carried out at full tillering stage. So the study of the persistance of isolated strains in wase carried out from pots in which we conducted a culture wheat. The results showed that the two bacteria persist for a limited period on the foliage unlike soil constitutes a seat favorable of development of these two microorganisms.  Keywords : Bacillus sp.(HE799656), Bacillus sp.(HE805963), persistence, wheat, leave, soil. 1-Introduction  In the context of biological control, several entomopathogenic microorganisms were used against insects and phytopathogenic diseases. The interest of these microbial insecticides has manifested as a result of many problems associated with the use of chemical insecticides (De Visscher, 1991). Before envisaging a release of entomopathogenic microorganisms in the environment, it is essential to choose an appropriate method of application and know all about its persistence in the environment, its reproductive potential, its potential for dispersal outside the application sites and its effects on the equilibrium and functioning of ecosystems exposed (Joung and Côté, 2000). It is in this concept that our work in part, it consists in the study of the persistence of two entomopathogenic bacteria Bacillus sp. (HE799656) and Bacillus sp. (HE805963) on the foliage of winter wheat and soil. Material and methods Results Table 1: Evolution of the number of colonies of Bacillus sp. (HE799656) on foliage and soil. The results of the study of the persistence on the foliage of winter soft wheat and soil are given in number of colonies per unit leaf area and / or 10 mg of soil. From the results of Table 1, it is observed that the number of bacteria Bacillus sp. (HE799656) persistent on foliage decreases with time until the total disappearance 9th day. For cons, the persistence of this bacterium in the soil remains stable throughout the period of experimentation with an average of 239 colonies recorded on the last day. . Number of colonies on the foliage Number of colonies in the soil P1 P2 P3 A ±δ 1 44 51 52 49 ± 4,35 202,5 179 300 227,16±64,16 3 37,5 55 40,5 44,33± 9,35 195 133,5 275 204,25±70,75 6 16,5 22 18 18,33 ±2,84 210 125 211,66±87,51 9 270 147,5 239,16± 80,79 P : Pot, A : Average Table 2: Evolution of the number of colonies of Bacillus sp.(HE805963) on foliage and soil. Number Day Number of colonies on the foliage Number of colonies in the soil P1 P2 P3 A ±δ 1 98 102 76 92±14 59 70 62 63,66± 5 3 88 100 67 85±16 150 108 120± 26 6 92 90 90±2 142 138 126± 24 9 73 99 81 84,33±13 177 148 122 149± 27 P : Pot, A : Average The results reported in Table 2 show that Bacillus sp. (HE805963) persisted on the foliage and the number of colonies remained almost stable, also the persistence of this bacterium in the soil is increased during the 9 days. References  Discussion and Conclusion Ashnaei S. P., Sharifi T. A., Ahmadzadeh M. and Behboudi K., Interaction of different media on production and biocontrol efficacy of Pseudomonas fluorescens P-35 and Bacillus subtilis B - 3 against gray mould of apple. Journal of Plant Pathology,91: Caron J., Laverdiere L. et Belanger R., Recherche et développement de biopesticides et pesticides naturels à faible toxicité pour les organismes non ciblés et respectueux de l’environnement –Rapport final – Volet Phytopathologie. Québec, Ed. MDDEP, 278p. Davet P., Vie microbienne du sol et production végétale. Ed. INRA, Paris, 383 p. De Visscher, M.N., L'environnement et la lutte anti-acridienne, les perspectives et les contraintes de la recherche. In : Essaid A. La lutte anti-acridienne. Ed. AUPELF-UREF, John Libbey Eurotext, Paris © 1991, Fargues J., Rougier M., Goujet R. et Itier B., Effet de rayonnement solaire sur la persistance des conidiospores de l’hyphomycète entomopathogènes, Nomuraea rileyi, à la surface d’un couvert végétal. Entomophaga, 33(3) : Joung J. et Côté J. C., Une analyse des incidences environnementales de l’insecticide microbien Bacillus thuringiensis. Ed.AAC. Centre de recherche et développement en horticulture, Bulletin technique n.29, Canada. The persistence of entomopathogenic microorganisms in the environment depends on several factors , the main ones are sun exposure, temperature, vapor pressure deficit, solar radiation and precipitation. The persistence of two bacteria studied is better in the ground. In fact, the majority of bacteria of the genus Bacillus are of telluric origin, they derive their nutritional needs of organic matter and mineral salts present in soil (Davet, 1996 and Ashnaei et al., 2009). Caron et al. (2006) found that certain strains of Bacillus sp. grow on plant organs where they release compounds that reduce competition for space and nutrients.