Arbuscular Mycorrhizal Fungi Colonizing Maize Genotypes Under Two Contrasting Water Levels.

Arbuscular mycorrhizae (AM) improve water and nutrient acquisition through plant root colonization and extension of hyphae into soil surrounding the root. In exchange, the AM symbiont receives carbon from the host plant. This exchange is governed by complex interactions among the plant, the fungus, and the environment. Plant and fungal genotypes, and the soil environment all contribute to the outcome of the symbiosis. Plant genotypes may respond differently to AM inoculation thereby affecting crop water and nutrient use efficiency.  The objective of this study was to assess AM colonization of drought tolerant maize genotypes grown in the field under two different water levels. Six drought sensitive hybrids were selected from a field experiment where 98 drought sensitive and tolerant maize hybrids (topcrosses) were tested for drought tolerance. Drought was imposed by two water levels (Well watered, WW, defined as the amount of water applied to raise a good crop in western NE; water stressed, WS, defined as 40% the amount of water as WW) in southwestern Nebraska in 2012. The experiment was arranged in a randomized complete block design with 2 blocks/repetitions per water level. Blocks 1 and 3 were WW and blocks 2 and 4 were WS, and were alternatively arranged on a field area irrigated by a pivot irrigation system. Three 20 cm deep soil samples per maize hybrid and water level were taken and a composite soil sample was made for each hybrid-water level combination. Soil pH, electrical conductivity and phosphorus content were determined in soil samples. Percent root colonization by AM fungi was measured in roots, and a AM fungal biomarker (C16:1cis11) was measured in soil. Plant and ear heights and maize grain yield were recorded at the end of the experiment.