Sorghum is an important cereal food crop in many parts of the world, often cultivated and consumed in low- and middle-income countries and frequently grown with low fertiliser inputs. Past research has shown that sorghum can be highly colonised by arbuscular mycorrhizal (AM) fungi and that the relationship between the plant and the AM fungi can lead to improvements in yield and nutritive content.

As a Ramsay fellow with the University of Adelaide, Dr Stephanie Watts-Fawkes used the APPF’s Adelaide Node’s high-throughput phenotyping to non-destructively interrogate the hidden effects of AM fungi on sorghum growth and phenology.

“I am very interested in investigating how AM can improve plant zinc and phosphorous nutrition in nutrient-depleted soils, and as a result maximise the availability of micronutrients in sorghum grain (such as zinc and iron), for the benefit of human health,” said Dr Watts-Fawkes.

“In this research, we looked at the responses to mycorrhizal inoculation when phosphorous (P) is limiting or when P fertiliser is applied. We wanted to see how mycorrhizal growth responses differed in eight diverse sorghum genotypes, and also measure grain quality for human nutrition such as phytate (the means for a plant to store phosphorous) of the resulting grain.

“The research showed sorghum plants colonised by AM fungi generally performed better than non-AM control plants, with greater yield, harvest indices, and grain P, Zn and Fe contents,” she added.

The high throughput phenotyping also revealed that mycorrhizal fungi negatively and temporarily affected the vegetative growth when the plants are young, and also affected time of flowering in some genotypes. This was illustrated when the sorghum genotype with the highest AM colonisation could barely produce grain when non-inoculated, and two genotypes with very low AM colonisation failed to mature.

The research showed that the plants colonised by the fungus were also more tolerant of low soil P concentrations and had greater grain yields than those not, and the increased phytate accumulation in grain of colonised plants was matched by increased Zn and Fe uptake, with a net neutral effect on bioavailability but with more yield.

Overall, the effects of AM colonisation on sorghum grain yield and nutrition were positive, which is an important finding for the future management of sorghum as a staple human food source both for its calories and nutrients. These are promising results for low input (fertiliser) farming systems where ideally mycorrhizal fungi would be managed well and phosphorus fertiliser applications could be reduced. This work is important for the future management of sorghum as a staple human food source both for its calories and nutrients.

You can read the paper here.