Abstract:
Sclerotinia sclerotiorum is an important pathogen of canola and many other
crops worldwide. Genetic diversity and population differentiation of S.
sclerotiorum collected from canola fields in Anhui Province, China (30
isolates) and in North Dakota, U.S.A. (29 isolates) were investigated in terms
of genetic variation in 8 simple sequence repeat (SSR) marker loci, mycelial
compatibility groups (MCGs) and three phenotypic traits: sensitivity to
fungicides benomyl, iprodione and fluzinam, oxalic acid production, and
pathogenicity. Significant genetic differences were observed; there were no
shared SSR haplotypes and no shared MCGs between the two populations.
Population differentiation was significant (p = 0.000) indicating lack of gene
flow between the two populations. There were also significant differences
between the two populations in oxalic acid production and in fungicide
sensitivity. The Chinese population displayed high levels of insensitivity
(faster growth rate) to benomyl and fluzinam and higher levels of oxalic acid
production per unit dry weight of mycelium than did the U.S. population.
However, there was no significant difference in pathogenicity between the
two populations as measured by colonization of detached canola leaves. Data
Vol. 101, No. 6 (Supplement), 2011 S11
suggest that despite geographic and genetic isolation the two populations of S.
sclerotiorum were equally adapted to colonizing canola plants, and
pathogenicity is under different selection pressure than the other genetic and
phenotypic traits.