Abstract:
Fungi in the Botryosphaeriaceae are important plant pathogens that persist endophytically
in infected plant hosts. Lasiodiplodia theobromae is a prominent species in this family that infects
numerous plants in tropical and subtropical areas. We characterized a collection of 255 isolates
of L. theobromae from 52 plants and from many parts of the world to determine the global genetic
structure and a possible origin of the fungus using sequence data from four nuclear loci. One to two
dominant haplotypes emerged across all loci, none of which could be associated with geography or
host; and no other population structure or subdivision was observed. The data also did not reveal a
clear region of origin of the fungus. This global collection of L. theobromae thus appears to constitute a
highly connected population. The most likely explanation for this is the human-mediated movement
of plant material infected by this fungus over a long period of time. These data, together with related
studies on other Botryosphaeriaceae, highlight the inability of quarantine systems to reduce the
spread of pathogens with a prolonged latent phase.
Description:
Supplementary material. Figure S1: Maximum likelihood tree of the tef1a sequence dataset for the initial identification of isolates for
inclusion in this study. Included were type and paratype strains of other Lasiodiplodia species, Figure S2:
STRUCTURE output from pairwise comparisons of populations. Each plot includes the DeltaK analysis from
STRUCTURE HARVESTER (top) and the corresponding barplot for the highest value of K. Pairwise comparisons
as follows: (a) north America and south America, (b) north America and Africa, (c) north America and Eurasia,
(d) north America and Australasia, (e) south America and Africa, (f) south America and Eurasia, (g) south
America and Australasia, (h) Africa and Eurasia, (i) Africa and Australasia and (j) Eurasia and Australasia, Table
S1: Polymorphic sites for the respective haplotypes for the ITS, tef1a and tub2 datasets, Table S2: Haplotype
assignments for every isolate used in this study, based on the sequence datasets, Table S3: Summary of haplotypes
obtained and unique haplotypes (listed in brackets) found for each locus, Table S4: Posterior probabilities (with
95% confidence intervals in parentheses) of pairwise comparisons for three scenarios to test for possible ancestry
between populations done in DIYABC. In scenario 1, population 1 is ancestral to both. In scenario 2, population 2
is ancestral to both. In scenario 3, both populations diverged from an unknown source population.
