Impact of mycorrhizal infection on sensitivity of wheat to sorghum allelopathy
M. M. ABDELKARIM (1), R. J. Gualandi (1), K. D. Gwinn (1), B. H. Ownley (1)
(1) University of Tennessee, Knoxville, TN, U.S.A.
Phytopathology 100:S2

Sorgoleone, an allelochemical exuded from the roots of sorghum, decreases growth of subsequent crops. The aim of this experiment was to determine impact of two species of mycorrhizae (Glomus intraradices or Gigaspora margarita) on allelopathic effects of sorghum (Sorghum bicolor Dekalb ‘DK39Y’) on wheat (Triticum aestivum Pioneer ‘26R22’). Sorghum plants were planted either in the presence or absence of mycorrhizae-infected sorghum roots. Vegetative growth of sorghum was removed after 12 weeks, and wheat (20 seeds/pot) was grown for one month in medium containing sorghum roots. The experiment had eight replicates with four treatments: no sorghum (control), non-mycorrhizal sorghum, Glomus-infected sorghum, and Gigaspora-infected sorghum. All growth parameters (shoot height, fresh shoot weight, fresh and dry root weights, and stem diameter) were greater for control than treatments that followed sorghum [P < 0.0001 for all parameters except stem diameter (P = 0.009)]. Plant height of mycorrhizal treatments was significantly higher than the non-mycorrhizal treatment, but there were no differences between mycorrhizal species (P < 0.0001). Root weight (fresh and dry) was greater in treatment with Gigaspora than in treatment with Glomus; neither was different from non-mycorrhizal treatment (P < 0.0001). In a natural infestation, the bird cherry oat aphid, Rhopalosiphum padi, was preferentially attracted to the non-mycorrhizal sorghum treatment (33.5 ± 8.1 aphids/plant); other treatments had fewer than one aphid/plant.