How do crop domestication and improvement reshape the root system and microbial community?

Modern agriculture highly depends on the achievements of crop domestication and improvement. While these activities increase yields, they also reduce the genetic diversity of crops. At the same time, as a key organ for plants to absorb nutrients and water, the root system's microbial community is of great significance to plant health and growth. So, what are the impacts of domestication and improvement on crop root functions and related microbial communities?

The research team led by Professor Peng Yu from the University of Bonn in Germany deeply explored this issue. The research was recently published in the journal Frontiers of Agricultural Science and Engineering (DOI: 10.15302/J-FASE-2024593).

The study found that crop domestication and improvement have significantly reshaped the structure and function of root traits and related microbial communities. In terms of root traits, domestication has changed the length and density of lateral roots, the number of radicles, the length of the main root, etc. of crops. Taking maize as an example, during the domestication process, the number of its radicles increased, but the lateral root density decreased, the root hair length shortened, the root diameter decreased, and the specific root length increased. In the subsequent modern improvement process, the lateral root density of maize increased again, the main root length became longer, and the size of cortical cells increased.

The structure and function of the microbial community have also been profoundly affected. During the evolution from wild crops to modern crops, the relative abundances of various microorganisms have changed significantly. For example, the number of arbuscular mycorrhizal fungi decreased during the domestication of maize but was enriched in modern maize hybrids; Pseudomonas is more common in the rhizosphere of maize hybrids. In the evolutionary process of common bean, from wild ancestors to landraces and then to modern varieties, the relative abundances of Chitinophagaceae and Cytophagaceae in the rhizosphere gradually decreased, while those of Nocardioidaceae and Rhizobiaceae gradually increased. These changes in the composition of the microbial community play an important role in aspects such as crop nutrient absorption and immune capacity.

Further exploring the mechanisms, some researchers found that crop domestication and improvement affect the assembly and function of the microbial community through gene regulation, alteration of root structure and function, and characteristics of root exudates. For example, the maize domestication gene teosinte branched1 can regulate root development and change the composition of the rhizosphere microbial community; due to differences in gene expression, the structure and function of the rhizosphere microbial community of hybrid maize are different from those of its parents. During the domestication of wheat, from wild strains to modern varieties, plant defense metabolites, antioxidants, plant hormones, and proteinogenic amino acids in grains increased significantly. And during the domestication process from wild emmer to emmer to durum wheat, the patterns of different metabolites (such as fructose, mannitol, and sorbitol) in the rhizosphere varied depending on the soil type. These changes in root exudates have a profound impact on the microbial communities in the rhizosphere and within the roots.

This study summarizes the current research status of the impacts of crop domestication and improvement on root characteristics and the structure and function of related microbial communities, deeply analyzes the influencing mechanisms, and provides a solid theoretical basis for future breeding work.