322 Influence of Mycorrhiza and an Isoflavonoid on Plant Growth and Gas Exchange of Potatoes Started from Minitubers

Abstract

The influence of the mycorrhizal fungus Glomus intraradices and reduced levels of G. intraradices treated with the isoflavonoid formononetin was tested on growth and gas exchange of container-grown potato plants. Tissue culture-produced minitubers of Solanum tuberosum cv. Russet Norkotah and Russet Norkotah selection TX112 were subjected to four treatments: 1) G. intraradices at 750 propagules per container, 2) G. intraradices at 376 propagules per container, 3) G. intraradices at 376 propagules per container treated with the isoflavonoid formononetin, and 4) noncolonized plants. Plants were grown under glasshouse conditions in 1500-mL containers containing a sterilized sand: sandy loam soil, and fertilized with Long Ashton nutrient solution modified to supply phosphorus at 11 ug P/mL. The experiment was initiated on 4 May 1998 and terminated on 27 Aug. 1998, during which the plants were exposed to adverse high temperatures (mean high: 30.7 °C). Both cultivars responded similarly to mycorrhizal treatments. Formononetin enhanced growth of myocorrhizal plants and increased total colonization, arbuscule, and hyphae development. Only formononetin-treated mycorrhizal plants had increased shoot growth. Net photosynthesis and stomatal conductance were generally greatest with reduced levels of mycorrhiza and formononetin treated mycorrhizal plants.