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Caractérisation phénotypique et génotypique des souches de Botrytis cinerea ; agent causal de la pourriture grise sur tomate

Abstract : Gray mold, caused by Botrytis cinerea fungus, is a major aerial fungal disease, which affects various important agronomical crops. Phenotypic and genotypic diversity of B. cinerea is very strong and its quick adaptability to selective pressure was reported, which makes the control methods very limited. The objectives of this work aim to study the phenotypic variability exhibited by isolates of B. cinerea in response to high temperatures. This by studying firstly the development of gray mold and temperature fluctuations in commercial tomato greenhouses in the region of Bejaia during two seasons (2012 and 2013), and then, by studying of the effect of temperature on the mycelial growth and spore germination of local isolates. The effect of high temperatures on the development in vitro, aggressiveness on tomato leaflets of B. cinerea isolates collected from different geographical regions (Algeria, France and Norway), as well as the aggressiveness of these isolates on tomato plant in optimal conditions were reported. A final objective aims to study the genotypical variability of B. cinerea populations isolated in tomato greenhouses of Bejaia region. The development of gray mold in tomato greenhouse, despite the high air temperatures recorded inside unheated greenhouse, which is confirmed by the rate of infected plants from the beginning (3.02%) and end of the experiment (25%), respectively. A significant difference was found between local isolates on spore germination and mycelial growth rate differences. Over 90% of the spores were germinated at 21 °C, whereas at 28 °C and 30 °C, spore germination was reduced to less than 79% and 50% respectively after 10 hours. The mycelial growth rate was significantly reduced at 28 °C and 30 °C for all tested isolates. No isolates were developed at 32 °C. The effect of temperature on the aggressiveness of B. cinerea isolates on tomato leaflets and full plants revealed considerable variability between tested isolates. Temperature of 30 °C corresponds to the inhibition of aggressiveness on tomato leaflets. No significant differences in aggressiveness were detected among isolates of B. cinerea collected in Algeria, France and Norway. Finally, a genotypic analysis of 174 isolates using nine microsatellite markers identified four of these isolates as Botrytis pseudocinerea based on the size of the allele at locus Bc6. For all other isolates studied, all loci are polymorphic, with an average number of alleles per locus from 2.77 to 5.22. Considerable genetic variability was detected in all subpopulations (D*>0.87; HNB>0.40). Based on the analysis of the standardized index association, a significant low level of clonality was observed, without excluding the possibility of recombination (rD=0.07, P<0.001). A total of 109 haplotypes were characterized, some of which were shared between sub-populations. Genetic differentiation was moderate between sub-populations according to geographical origin (0.080 B. cinerea populations was discussed and should be considered for the management of gray mold.
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  • HAL Id : tel-02800419, version 1
  • PRODINRA : 361576

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Ahmed Adjebli. Caractérisation phénotypique et génotypique des souches de Botrytis cinerea ; agent causal de la pourriture grise sur tomate. Sciences agricoles. Université Abderrahmane Mira de Béjaïa, 2015. Français. ⟨tel-02800419⟩

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