The genetic diversity of water use efficiency in the nested associated mapping population of Zea mays
Abstract
Climate change and increasing incidence of drought worldwide have highlighted the need for improvement of water use efficiency (WUE) in many crops and improved WUE is one of the key components to improving maize production in the world. We used the 26 nested association mapping (NAM) founder genotypes and testcrosses made from these genotypes to identify the physiological and genetic bases for WUE in maize. Instantaneous water use efficiency (WUEi) of field-grown plants ranged from 4.03 to 9.20 µmol mmol-1 and whole plant biomass water use efficiency (WUEb) of greenhouse-grown plants ranged from 3.97 to 8.38 g kg-1. Nighttime water loss ranged from 11.5 to 22.4 g cm-2, but was not correlated with WUE. In all environments, genetic variation for WUE and related traits was low. However, Mo17 and CML333 were high WUE genotypes in both field and greenhouse environments. Transpiration was correlated with WUEi, whereas stomatal density was not correlated with WUE or related traits. Field and greenhouse WUE measurements were not correlated. Carbon isotope discrimination (δ13C) is related to WUE in some crops such as wheat, rice, and tomato. Heritability of leaf δ13C among the NAM founder lines was 0.51, ranged from -11.78 to -13.08‰, and was positively correlated with transpiration, net CO2 assimilation, stomatal conductance, and intrinsic water use efficiency (WUEin). QTL were identified for percent carbon, days to anthesis, and days to silking, but not leaf δ13C and ASI in hybrids derived from the NAM founders. The inability to identify QTL for leaf δ13C may be due to heterosis, low heritability, and/or lack of replication. Genetic diversity for WUE in the NAM founders was lower than expected, but genotypes such as Mo17 consistently showed high WUE with low leaf δ13C suggesting that this genotype may be used to identify the genetic basis of WUE.
Degree
M.S.
Advisors
Mickelbart, Purdue University.
Subject Area
Agronomy|Plant sciences
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