Endomycorrhizal Fungi in Breeder Wheats and Triticale Cultivars Field-Grown on Fertile Soil1
- J. L. Young,
- E. A. Davis and
- S. L. Rose2
A survey of four cereal research fields growing various commercial and breeder wheat (Triticum aestivum L.), and triticale (X Triticosecale), cultivars revealed the presence of several endomycorrhizal fungi in soils with elevated levels of available P. Extractable (Bray) P levels of sampled fields ranged from 73 to 119 mg kg−1-this in an area where unirrigated wheat yields may exceed 5500 kg ha−1 (> 100 bu acre−1) and the Extension Service “Fertilizer Guide” calls for no P fertilizer additions on grains when soil test values for P are >30 mg kg−l. Cortex colonizations among the >60 breeder and commercial wheat cultivars (sampled just preharvest) were variable and relatively low (range <2 to >18%) partly due to declining root tissues at this stage. Atrophied fine feeder roots and degraded cortical areas were common, yet, in many cases, moderately abundant external hyphae remained adherent to weakened root segments, despite rigors of washing, clearing, and staining. Triticale roots, among the 12 cultivars sampled, were also colonized but at lower percentages (range, 1 to 13%). Vesicular-arbuscular mycorrhizal (VAM) fungi isolated from the well-fertilized fields included several Glomus spp., Acaulospora laevis, and an occasional Sclerocystis sporocarp. The A. laevis and a Glomus mosseae type were by far the most common endophytes in terms of spores recovered. Of these isolates tolerating the plentiful soil P status, the Gl.. mosseae-type spores predominated at pH‘s 5.7 and 6.3. Acaulospora laevis spores greatly dominated in the strongly acid field (pH 4.3 to 4.8) although the Gl. mosseae began to reestablish/recompete where liming nudged the soil back to ~pH 5.7. The abundance of A. laevis spores found with the monocotyledonous wheats contrasts with a published suggestion that Acaulospora species develop in association with dicot hosts. One hopes that bioassay of such higher-fertility tolerant species will lead eventially to discovery of effective VAM fungal isolates that can still benefit crops despite high-input fertilizer, pesticide, or water management practices.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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