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Effect of seedborne Alternaria infectoria on susceptibility of wheat seedlings to Fusarium pseudograminearum

Sandra Lamprecht: Agricultural Research Council-Plant Health and Protection

<div>Seedborne fungi can affect the susceptibility of seedlings to soilborne pathogens. <em>Alternaria infectoria</em> is the dominant seedborne fungus on many commercial wheat cultivars in South Africa. This study investigated the effect of seedborne <em>A. infectoria</em> on the susceptibility of wheat seedlings to <em>Fusarium pseudograminearum</em>, an important soilborne pathogen of wheat in South Africa. Seedborne <em>A. infectoria</em> was eliminated from seed of 12 wheat cultivars using hot water treatment at 45°C for 3 hrs. Four isolates each of the two fungi were used to prepare spore suspensions of 2.5 x 10<sup>5</sup> spores/ml for each fungus, as well as a spore suspension containing a mixture of the two fungi also containing 2.5 x 10<sup>5</sup> spores of each fungus/ml. Hot water and non-hot water treated seed of the 12 wheat cultivars were plated on potato-dextrose agar for 5 days to germinate. The seedlings were then dipped in either the <em>Alternaria</em>, <em>Fusarium</em> or the mixed spore suspensions and planted in a pasteurized (83°C for 60 min) sand, perlite and soil (1:1:1 mixture) growth medium in a glasshouse (25°C day, 15°C night temperatures). Control seedlings were dipped in sterile water only. Crown rot severity was evaluated 28 days after planting. Results showed that <em>A. infectoria </em>did not affect the susceptibility of wheat seedlings to <em>F. pseudograminearum</em> and will therefore not interfere with screening of seedlings for resistance/tolerance to <em>F. pseudograminearum</em>.</div>