Microsatellite markers in the entomopathogenic fungus Paecilomyces fumosoroseus for monitoring of isolates introduced against Bemisia tabaci, epidemiological and population genetics studies [résumé]

2008

Article référencé dans le Web of Science WOS:000253056900033

Gauthier Nathalie, Bon Marie-Claude, Dalleau-Clouet Cécile, Fargues Jacques

Journal of Insect Science, 2008, 8 (4), p. 19 ISSN 1536-2442

International Bemisia Workshop ; International Whitefly Genomics Workshop, 4., Duck Key (USA), 2006/12/03-08

One of the greatest challenges for improving the use of fungi, not only as microbial control agents but also for all epidemiological and population genetics studies, is the ablity to identify the isolates used and analyzed. The haploid entomopathogenic hyphomycete Paecilomyces fumosoroseus (Pfr) used for biological control of economically serious agricultural pests is a geographically widespread fungus infecting various orders of insects. In particular, it is naturally associated with the whitefly Bemisia tabaci (Homoptera Aleyrodidae) in various geoclimatic regions. Ongoing difficulties in applying morphological approaches to isolate-recognition Pfr have spurred the search for discriminant markers. Based on rDNA-ITS RFLP approach, all isolates collected from B. tabaci clustered in 1 group although they originated from diverse geographical locations. Microsatellite markers were therefore developed and characterized in Pfr. Upon the 9 isolated, 8 were revealed as polymorphic. Amplification success and length and sequence variability of these markers were investigated on a set of 34 Pfr sampled from various insect-host species and geographical locations. First, PCR amplifications at the 9 previously designed loci were only successful with Pfr from Homoptera hosts (25 B. tabaci and 1 Phenacoccus sp. hosts) which has suggested existence of genotype host-associations. Second, allele size and above all sequence analyses (flanking microsatellite-regions and/or microsatellite regions) improve our ability to discriminatamong Pfr isolates and provide a means to subdivide isolates obtained from B. tabaci. Indeed, from a unique Pfr rDNA-ITS RFLP haplotype, 7 patterns based on specific microsatellite allelic-sizes and 14 haplotypes based on their sequencing were resolved from B. tabaci which emphasizes their value for further epidemiological studies and use in biological control. Finally, their value for genetic relationships inference was also proven and a phylogeographic framework was henceforth established providing evidence for two distinct lineages of Pfr, American-Cuban and Asian, with a putative Indian origin of the American-Cuban Pfr group from an Indian group. Consequently, the microsatellite markers described represent a potent tool for Pfr population diversity studies and open a new and informative window on the use of well-discriminated isolates in epidemiology and biological control strategy against B. tabaci.

Champignons [074MICFLO03]

Fonds IRD [F B010085568]

fdi:010085568