Variation among maize inbred lines and detection of quantitative trait loci for growth at low phosphorus and responsiveness to arbuscular mycorrhizalfungi

Maize (Zea mays L.) growth at low soil P levels is affected both by inheren t physiological factors as well as interactions with soil microbes. The obj ectives of this study were (i) to quantify differences among maize inbred l ines for growth at low P and response to mycorrhizal fungi, and (ii) to ide ntify quantitative trait loci (QTL) controlling these traits in a B73 X Mo1 7 recombinant inbred population. Shoot dry weight and root volume were meas ured in the greenhouse after 6 wk of growth in a factorial experiment of 28 inbred maize lines using treatments of low vs, high P and mycorrhizal vs, nonmycorrhizal treatments. Shoot dry weight for the low P treatment in the absence of mycorrhizae ranged from 0.56 to 3.15 g. Mycorrhizal responsivene ss based on shoot dry weight ranged from 106 to 800%. Shoot dry weight in t he low P-nonmycorrhizal treatment was highly negatively correlated with myc orrhizal responsiveness. Plants grown at high P in the presence of mycorrhi zae accumulated only 88% of the biomass of plants grown at high P in the ab sence of mycorrhizae, indicating that mycorrhizae can reduce plant growth w hen not contributing to the symbiosis. Percentage of root colonization was not correlated with mycorrhizal responsiveness. B73 and Mo17 were among the extremes for growth at low P and mycorrhizal responsiveness, and a B73 X M o17 population of 197 recombinant inbred lines was used to detect QTL for g rowth at low P and mycorrhizal responsiveness. Three QTL were identified wh ich controlled growth at low P in the absence of mycorrhizae based on shoot weight and one QTL which controlled mycorrhizal responsiveness. This study indicates that there is substantial variation among maize lines for growth at low P and response to mycorrhizal fungi. This variation could be harnes sed to develop cultivars for regions of the world with P deficiency and for reduced-input production systems.