The endophyte Neotyphodium coenophialum affects root morphology of tall fescue grown under phosphorus deficiency

Mechanisms involved in mineral stress tolerance of cool-season grasses infected by Neotyphodium spp. endophytes are not known. In a controlled-environment experiment, two genotypes (DN2 and DN4) of tall fescue (Festuca arundinacea Schreb.) infected (E+) with their naturally occurring strains of N. coenophialum (Morgan-Jones and Gams) Glenn, Bacon and Hanlin, and their non-infected (E-) isolines were cultivated in nutrient solution at two phosphorus (P) levels of 31 mg P dm(-3) (P+) and 0.31 mg P dm(-3)(P-)for 3 weeks. Diameters of lateral roots, root hair length, and distance between root hairs were recorded using a digital image analysis system (Dage 72S CCD camera controlled by a Power Macintosh 7200/120PC compatible computer equipped with an AG-5 frame grabber board and NIH-Image). Irrespective of tall fescue genotype and P level in nutrient solution, Ef plants had roots with a smaller diameter(16%) than E- plants. In response to P deficiency, root diameter of E+ plants declined by 11% and root hair length increased by 17% when compared to E- plants. Altered root diameter and root hair length might be one of the mineral stress tolerance mechanisms in endophyte-infected tall fescue.