# A maize landrace introgression library reveals a negative effect of root‐to‐shoot ratio on water‐use efficiency

## TL;DR

A study on maize found that reducing the root-to-shoot ratio can improve water-use efficiency, which is important for sustainable agriculture.

## Contribution

The study reveals a negative effect of root-to-shoot ratio on water-use efficiency in maize using an introgression library.

## Key findings

- Introgression of Gaspé Flint into B73 altered traits like shoot biomass and WUE.
- Seven major QTL clusters affecting shoot growth and WUE were identified.
- Reduced root-to-shoot ratio positively affects maize water-use efficiency.

## Abstract

Novel sources of genetic variability for water‐use efficiency (WUE) are needed in order to breed varieties more suitable to sustainable cropping systems. Here, a maize (Zea mays L.) introgression library of the landrace Gaspé Flint into the reference line B73 was characterized in high‐throughput phenotyping platforms, both in well‐watered and moderate water‐deficit conditions, for water use, WUE, and root and shoot growth. Traits heritability ranged from 0.77 to 0.93. The introgression of Gaspé Flint chromosome segments into the B73 genome significantly altered several traits. Some introgression lines exhibited a faster shoot biomass accumulation than B73, resulting in higher WUE at the expense of root growth. Quantitative trait loci (QTL) mapping identified seven major QTL clusters affecting shoot growth and WUE, two of which overlapped, with opposite effects, with QTLs for root biomass known to include root developmental genes. These results support the non‐intuitive hypothesis that reduced root‐to‐shoot ratio positively affects maize WUE.

A maize introgression library was phenotyped for water use, water‐use efficiency, root and shoot growth.Quantitative trait loci (QTL) mapping identified seven major QTL clusters affecting shoot growth and water‐use efficiency.Gaspé Flint landrace confers early vigor QTL haplotypes with beneficial effect on water‐use efficiency.Reduced root‐to‐shoot ratio positively affects maize water‐use efficiency.

A maize introgression library was phenotyped for water use, water‐use efficiency, root and shoot growth.

Quantitative trait loci (QTL) mapping identified seven major QTL clusters affecting shoot growth and water‐use efficiency.

Gaspé Flint landrace confers early vigor QTL haplotypes with beneficial effect on water‐use efficiency.

Reduced root‐to‐shoot ratio positively affects maize water‐use efficiency.