QTL mapping and phenotypic variation for root architectural traits in maize (Zea mays L.)

Abstract

QTL were identified for root architectural traits in maize. Root architectural traits, including the number, length, orientation, and branching of the principal root classes, influence plant function by determining the spatial and temporal domains of soil exploration. To characterize phenotypic patterns and their genetic control, three recombinant inbred populations of maize were grown for 28 days in solid media in a greenhouse and evaluated for 21 root architectural traits, including length, number, diameter, and branching of seminal, primary and nodal roots, dry weight of embryonic and nodal systems, and diameter of the nodal root system. Significant phenotypic variation was observed for all traits. Strong correlations were observed among traits in the same root class, particularly for the length of the main root axis and the length of lateral roots. In a principal component analysis, relationships among traits differed slightly for the three families, though vectors grouped together for traits within a given root class, indicating opportunities for more efficient phenotyping. Allometric analysis showed that trajectories of growth for specific traits differ in the three populations. In total, 15 quantitative trait loci (QTL) were identified. QTL are reported for length in multiple root classes, diameter and number of seminal roots, and dry weight of the embryonic and nodal root systems. Phenotypic variation explained by individual QTL ranged from 0.44% (number of seminal roots, NyH population) to 13.5% (shoot dry weight, OhW population). Identification of QTL for root architectural traits may be useful for developing genotypes that are better suited to specific soil environments.

Reduced Lateral Root Branching Density Improves Drought Tolerance in Maize

“…Plant breeders rarely select for root traits because they are challenging to phenotype, many traditional metrics of root phenotypes are actually phene aggregates with low heritability, and root phenotypes often display plasticity in response to soil conditions (Tuberosa et al, 2002;Malamy, 2005;York et al, 2013;Lynch, 2014). As shown here and in previous literature, genotypic differences in lateral root number and length exist in maize (Zhu et al, 2005b;Trachsel et al, 2011;Lynch, 2013;Burton et al, 2014). Previous studies indicate that lateral branching is a heritable trait (Zhu et al, 2005b), and genes affecting lateral branching have been identified in several species, including maize (Doebley et al, 1995) and rice (Takeda et al, 2003), making lateral branching and length feasible targets for plant breeding.…”

“…Each RIL is a distinct genotype, and comparison of several RILs allows the analysis of a phenotype in distinct genomes, thereby minimizing the risk of confounding effects from pleiotropy, epistasis, or other genetic interactions (Zhu and Lynch, 2004). RILs are particularly valuable in the analysis of phenotypic traits governed by multiple genes, as is the case for lateral rooting in maize (Zhu et al, 2005b;Burton et al, 2014).…”

QTL Identification for Brace‐Root Traits of Maize in Different Generations and Environments

“…Maize with a strong root system can resist abiotic stresses, such as strong wind, water shortage, low level of nutrients, etc. Furthermore, a moderate negative correlation was observed between the diameter and length of the main axis of the crown root in IBM and OhW families, and root length traits in the crown root were moderately correlated with the length of the seminal root in IBM at 28 d of growing in solid media in a greenhouse (Burton et al, 2014). Trachsel et al (2009) found that the elongation rate of axile roots, the number of axile roots, and the length of the primary root were significantly correlated with RDW at 9 d after germination.…”

Genetic dissection of maize seedling root system architecture traits using an ultra‐high density bin‐map and a recombinant inbred line population

“…Among these, hydroponics has been favored for precise control of nutrient concentration and the ease of phenotyping. Using this method, many QTL controlling lateral root number, primary root length and other traits have been identified at various water and nutrient regimes (Mano et al ; Zhu et al ; Liu et al ; Abdel‐Ghani et al ; Burton et al ; Kumar et al ).…”