Researchers in the US have identified some of the beneficial microbes which can be found around carrot roots, with a view to how they can be used to overcome harmful disease-causing organisms.
The team of university and Agricultural Research Service (ARS) scientists say their work is a critical step towards learning how carrot growers could enlist these beneficial microbes as an effective defence against diseases like Alternaria leaf blight.
They evaluated 36 diverse commercial carrot varieties and breeding lines for their reactions to Alternaria leaf blight in either conventionally managed or organically farmed plots. In the conventional plot, for example, pre-emergent herbicides were applied after the carrots had been planted, while in organic plot, weeds were hand-pulled as needed.
The researchers ranked the severity of Alternaria leaf blight in the carrots on a scale of 1 to 12 and harvested the vegetables. They grew cultures of endophytes from nine of lowest-scoring (healthiest) carrot varieties and identified them using DNA “fingerprinting” methods. They also conducted petri-dish and seed experiments confirming the endophytes’ anti-Alternaria activity.
The results showed that soils in organic plots had more organic matter, a greater diversity and abundance of endophytes, and plants grown in these plots had lower disease levels than conventional plots. Exactly how the endophytes protect carrots also isn’t well understood. One possible explanation is that ‘good’ microbes exclude Alternaria fungi, or that they secrete antibiotics.