The interaction of the roots with a common soil fungus changes the genetic expression of rice crops, triggering growth that allows the plant to absorb more nutrients.
In addition to causing extra root growth, 'mycorrhizal fungus' also entangles itself within the roots of cultures at the cellular level, flourishing within individual cells of the plant.
The fungus develops thin tendrils called hyphae that spread around the soil and inject nutrients, phosphate in particular, directly into the heart of plant cells.
Plants 'colonized' by the fungi get 70 to 100 percent of their phosphate directly from these fungus tendrils, a huge mineral boost that can eventually mitigate the need for farmers to saturate crop fields with phosphate fertilizers. to ensure maximum performance, according to this work, published in 'Proceedings of the National Academy of Sciences'.
The hope is that mycorrhizal fungi could one day act as biofertilizers that ultimately replace the need to extract phosphate from the soil as an industrial fertilizer.
Finding an alternative to phosphate mines is a critical problem as not only is the resulting fertilizer a contaminant, causing algae growth that chokes water supplies, but large phosphate mines are now depleted to the point where they are expected to be depleted in the next 30 to 50 years, with a possible phosphate crisis, many experts predict.
One of the authors of this work, Uta Paszkowski, from the Cambridge Department of Plant Sciences, believes that the big question is how to make use of the biofertilizing capacity of the mycorrhizal symbiosis in the most intensive cultivation methods.
"We need alternatives to phosphate fertilizer if we are going to feed the growing population," he says. "Cereals like rice, wheat and corn are the most important crops in the world, feeding millions of people every day.
Mycorrhizal fungi have a mutualistic relationship with plants, including cereals, dating back to the first days of plant life on earth, before roots were 'invented'.
By analyzing this ancient and common relationship we are gaining insights that could be used to breed crops with the best possible architectural and symbiotic properties at the root, tending towards designer crops with very high food yields, "he says.
The new research is groundbreaking in examining the roots of the root system of rice plants at the molecular level, because rice can be used as a model for cereal crops in general.
The 'architecture' of the cereal root involves a few large roots, called crown roots, which act as a scaffold from which all the smaller lateral roots are spread over the different layers of the earth, which contain the various nutrients.
The researchers found that plants colonized by mycorrhizal fungi have a different gene expression that causes the cell walls within the crown roots to soften, causing the growth of many more lateral roots that are capable of absorbing more nutrients, contributing to a healthier plant with a higher yield.
This is in addition to the phosphate provided by the hyphae of the fungal tendrils, which in effect act as additional roots themselves (in return, the fungus gets its carbohydrates from the plant).
Rice grows best in highly irrigated paddy fields, but there are many parts of the world where this is not an option, and 40 percent of the world's rice acreage is "dry."
However, the plant-to-fungus relationship that generates improved crops actually works best in dry environments.
Mycorrhizal fungi could be of great benefit to those who depend on dry rice crops in some of the poorest areas of Asia and sub-Saharan Africa. The main hurdle for researchers is overcoming plant self-regulation, which means that fungi cannot be tested on an industrial scale alongside traditional fertilizers.
"Plants control their own nutritional status.
If a plant has enough phosphate, it will not allow the fungus to enter the root so at this point it is either one. We are working on ways to bypass this blockade in order to allow symbiosis to contribute to better agricultural practices in developed countries, "says Paszkowski.
Mycorrhizal fungi are very common in all soils around the world and are an ingredient in many 'bio' plant foods found in national garden centers, but have not yet been used for industrial agriculture.