Host resistance mediated inter-genotype competition and temporal variation in <Emphasis Type="Italic">Fusarium oxysporum</Emphasis> f. sp. <Emphasis Type="Italic">vasinfectum</Emphasis> |
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Authors: | B Wang C L Brubaker P H Thrall J J Burdon |
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Institution: | (1) CSIRO Plant Industry, G.P.O. Box 1600, Canberra, ACT 2601, Australia;(2) Present address: Bayer BioScience N.V., Technologiepark 38, 9052 Ghent, Belgium |
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Abstract: | Temporal variation in Fusarium oxysporum f. sp. vasinfectum (Fov) populations was determined by comparing the genetic diversity of pathogen isolates recovered from three consecutive cotton
crops (2002, 2004 and 2006) in the Boggabilla area of New South Wales, Australia. A total of 288 isolates were collected,
among which 25 distinct AFLP genotypes were identified. These genotypes were classified into two main groups corresponding
to known vegetative compatibility groups (VCG)—01111 and 01112. The Fov populations were dominated by four genotypes (I-A, I-B, II-A, II-B) that accounted for 87.5% of the isolates. Significant
temporal variation was observed in both sampled fields with 6.8% and 10.7% of total genetic variation being attributed to
differences among collections in different years. Genetic diversity based on Nei’s gene diversity and the Shannon-Wiener index
increased over time. Significant changes in the frequency of the dominant Fov genotypes were observed in one field, where genotype I-A declined from 84.8% to 40.0% over the study period (2002–2006),
while genotype I-B increased from 7.6% to 35.4%. Strong inter-genotype competition was detected in glasshouse bioassays with
93.4% of symptomatic plants sampled from dual inoculation trials being infected by single genotypes. Competition was differentially
mediated by cotton cultivars as the competitive ability of pathogen genotype I-B was enhanced on the resistant cultivar Sicot
189 relative to the susceptible cultivar Siokra 1–4. This suggests that host-mediated inter-genotype competition may play
an important role in temporal variation in Fov populations in the field. |
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