Agri Kultuur December / Desember 2018 - Page 22

and even season can also affect the outcome. To work properly, fungal biofertilizers also need to be compatible with local conditions, including the microbes that are already present in the soil. A crucial question is whether the inoculant fungi are superior competitors to the “native” fungi already established? What’s more, little is known of the long-term effects of introducing these fungi to the soil and surrounding ecosystem. Fungal friends or foes? Mycorrhizal fungi can also have negative effects on crops. In our research, my colleagues and I explored the effects of an arbuscular mycorrhizal fungal community on the growth of wheat and its resistance to tiny worms that attack the roots. These pests, called plant-parasitic nematodes, cause an estimated US$80 billion per year in crop damage. Arbuscular mycorrhizal fungi reduced crop growth and suppressed important defence- related compounds which may have caused an increase in nematode populations in the soil. Created with ‘Biorender’ We found that fungal inoculation reduced plant growth and suppressed important defence-related compounds in the roots. We also observed an increase in nematode populations in the soil, potentially due to lowered plant defences. Of course, this is only one example. And this experiment was not done in the field. AgriKultuur |AgriCulture Yet it is not the only study to have identified potentially negative consequences of biofertilizers. Soil probiotics Biofertilizers are like gut probiotics, in that both approaches aim to inject “good” microbes into places where they will prove beneficial. But just as the widely touted health benefits of gut probiotics don’t work for everyone, our results paint a similar picture for soil fungi. Put simply, there isn’t a one-size-fits-all fungal biofertilizer that will boost every crop in every environment. But that doesn’t mean we shouldn’t work towards improving our ability to use these fungi. In fact, this should be a priority – biofertilizers can be a powerful tool to help tackle the challenges posed by population growth and climate change. In the right situation, biofertilizers can dramatically increase crop yields and pest resistance, potentially helping us grow more food, more sustainably. But we need to learn more before we can turn this ancient symbiosis between plants and fungi to our advantage. Acknowledgement Adam Frew: Postdoctoral Research Fellow, Charles Sturt University: ‘Soil probiotics’ promise bigger, healthier crops, but there’s a downside; Published in https:// promise-bigger-healthier-crops-but-theres- a-downside-103236 October 23, 2018. Republished under 22