Genetic Variability in Phosphorus Responses of Rice Root Phenotypes

Abstract

BackgroundLow phosphorus availability is a major factor limiting rice productivity. Since root traits determine phosphorus acquisition efficiency, they are logical selection targets for breeding rice with higher productivity in low phosphorus soils. Before using these traits for breeding, it is necessary to identify genetic variation and to assess the plasticity of each trait in response to the environment. In this study, we measured phenotypic variation and effect of phosphorus deficiency on root architectural, morphological and anatomical traits in 15 rice (Oryza sativa) genotypes. Rice plants were grown with diffusion-limited phosphorus using solid-phase buffered phosphorus to mimic realistic phosphorus availability conditions.ResultsShoot dry weight, tiller number, plant height, number of nodal roots and shoot phosphorus content were reduced under low phosphorus availability. Phosphorus deficiency significantly reduced large lateral root density and small and large lateral root length in all genotypes, though the degree of plasticity and relative allocation of root length between the two root classes varied among genotypes. Root hair length and density increased in all genotypes in response to low phosphorus. Nodal root cross-sectional area was significantly less under low phosphorus availability, and reduced cortical area was disproportionately responsible for this decline. Phosphorus deficiency caused a 20 % increase in the percent cortical area converted to aerenchyma. Total stele area and meta-xylem vessel area responses to low phosphorus differed significantly among genotypes. Phosphorus treatment did not significantly affect theoretical water conductance overall, but increased or reduced it in a few genotypes. All genotypes had restricted water conductance at the base of the nodal root compared to other positions along the root axis.ConclusionsThere was substantial genetic variation for all root traits investigated. Low phosphorus availability significantly affected most traits, often to an extent that varied with the genotype. With the exception of stele and meta-xylem vessel area, root responses to low phosphorus were in the same direction for all genotypes tested. Therefore, phenotypic evaluations conducted with adequate fertility should be useful for genetic mapping studies and identifying potential sources of trait variation, but these should be confirmed in low-phosphorus environments.Electronic supplementary materialThe online version of this article (doi:10.1186/s12284-016-0102-9) contains supplementary material, which is available to authorized users.

Genetic Control of Plasticity in Root Morphology and Anatomy of Rice in Response to Water Deficit

“…2G) in roots, decreases radial distance, and improves radial hydraulic conductivity. The reduced CD also could significantly reduce the roots' metabolic cost of soil exploration, thereby improving water and nutrient acquisition in waterdeficit and nutrient stress (Chimungu et al, 2014;Vejchasarn et al, 2016). However, reduced CD reduces root thickness (Fig.…”

Comparing Phenotypic Variation of Root Traits in Thai Rice (Oryza Sativa L.) Across Growing Systems

“…Root excavation was carried with the shovelomics protocol described in Trachsel et al (2010) and Vejchasarn et al (2016). Root crowns were collected by excavating a 15-cm radius around the stem to a depth of at least 15 cm.…”

“…Root hair evaluation was carried out as described by Vejchasarn et al (2016). Primary root or crown root samples were stained with 0.5% of toluidine blue for 45 s before the images of the root hairs were taken.…”

“…This scenario poses significant economic challenges to large-and small-scale rice farmers. Improved rice varieties with http://www.aloki.hu • physiological studies in rice (Vejchasarn et al, 2016). In the field, shovelomics, a manual high throughput approach, facilitates the evaluation of mature root architecture (Trachsel et al, 2011).…”

A New Phenotyping Pipeline Reveals Three Types of Lateral Roots and a Random Branching Pattern in Two Cereals

“…Finally, the plasticity of the proportions of these different lateral root types also could contribute to the efficiency of the root system. In rice, the proportions of short and long lateral roots are highly plastic in response to low phosphorus, and there exists some genetic variability of this plasticity (Vejchasarn et al, 2016). The role of type B lateral roots is more speculative, but they could constitute a tradeoff between the two opposite strategies of type A and C lateral roots.…”