Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/25/2013
Publication Date: 6/1/2013
Citation: Mammella, M., Martin, F.N., Cacciola, S.O., Coffey, M.D., Faedda, R., Schena, L. 2013. Analyses of the population structure in a global collection of Phytophthora nicotianae isolates inferred from mitochondrial and nuclear DNA sequences. Phytopathology. 103(6):610-622. Interpretive Summary: This manuscript investigates the population biology of Phytophthora nicotianae, a plant pathogen with a wide host range and distribution around the world. DNA sequences were generated from four mitochondrial regions and three nuclear encoded genes from a range of isolates and used to model the pathogens population structure.
Technical Abstract: Genetic variation within the heterothallic cosmopolitan plant pathogen Phytophthora nicotianae was determined in 96 isolates from a wide range of hosts and geographic locations by characterizing four mitochondrial (10% of the genome) and three nuclear loci. Fifty-two SNPs ( average of 1 every 58 bp) and 313 sites with gaps enabled the identification of 50 different multilocus mitochondrial haplotypes. Similarly, 24 SNPs (average of 1 every 69 bp), with heterozigosity observed at each locus, were observed in three nuclear regions (hyp, scp, ß-tub) differentiating 40 multilocus nuclear genotypes. Both mitochondrial and nuclear markers revealed a high level of dispersal of isolates with a typical panmictic distribution and lack of association with geographic origin. However, a specific association for some isolates was observed for host of origin and genetic grouping with both nuclear and mitochondrial sequences. In particular, the majority of citrus isolates from Italy, California, Florida, Syria, Albania and Philippines clustered in the same mitochondrial group and shared at least one nuclear allele. Although less evident, a similar association was also observed for isolates recovered from tobacco. On the whole, the present study suggests the existence of extensive phenomena of gene flow and migration of isolates. P. nicotianae isolates have been likely spread worldwide with infected plant material (nursery trade).