Variation among Maize Inbred Lines and Detection of Quantitative Trait Loci for Growth at Low Phosphorus and Responsiveness to Arbuscular Mycorrhizal Fungi

Abstract

Maize (Zea mays L.) growth at low soil P levels is affected both by inherent physiological factors as well as interactions with soil microbes. The objectives of this study were (i) to quantify differences among maize inbred lines for growth at low P and response to mycorrhizal fungi, and (ii) to identify quantitative trait loci (QTL) controlling these traits in a B73 × Mo17 recombinant inbred population. Shoot dry weight and root volume were measured 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 responsiveness based on shoot dry weight ranged from 106 to 800%. Shoot dry weight in the low P–nonmycorrhizal treatment was highly negatively correlated with mycorrhizal responsiveness. Plants grown at high P in the presence of mycorrhizae accumulated only 88% of the biomass of plants grown at high P in the absence of mycorrhizae, indicating that mycorrhizae can reduce plant growth when 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 × Mo17 population of 197 recombinant inbred lines was used to detect QTL for growth at low P and mycorrhizal responsiveness. Three QTL were identified which 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 harnessed to develop cultivars for regions of the world with P deficiency and for reduced‐input production systems.

Root Cortical Aerenchyma Enhances Nitrogen Acquisition from Low-Nitrogen Soils in Maize

“…Seeds of maize (Zea mays) RILs from the Intermated B73 and Mo17 (IBM) population were obtained from Dr. Shawn Kaeppler (University of Wisconsin, Madison;Senior et al, 1996;Kaeppler et al, 2000). Previous screening indicated that RILs 337, 133, and 177 had low RCA and RILs 196,199, and 345 had high RCA under low-N conditions.…”

Plant species differ in their ability to reduce allocation to non‐beneficial arbuscular mycorrhizal fungi

“…Root colonization varied more widely in the C 3 than in the C 4 grasses, corresponding with stronger reductions in allocation to AMF at high phosphorus in C 3 than C 4 grasses. Root colonization is at best a weak predictor of carbon and nutrient exchange (Noyd et al 1995, Wilson and Hartnett 1998, Kaeppler et al 2000, Jifon et al 2002, so it is surprising that this response was associated with effective reductions in allocation to non-mutualistic AMF.…”

Mapping Density Response in Maize: A Direct Approach for Testing Genotype and Treatment Interactions

“…Both inbred lines (Mo17, B73) and the B73 3 Mo17 hybrid have been extensively studied. As a result, QTL studies for several traits performed on the progeny of this cross have been published (Stuber et al 1992;Kaeppler et al 2000;Mickelson et al 2002;Carson et al 2004). Seed for the eight selected SILs and their crosses to inbred line Mo17 was increased in the winter of 2003 in Puerto Rico.…”