Jan 15, 2020
In this episode of the Regenerative Agriculture Podcast, John Kempf interviews plant pathologist Dr. James White of Rutgers University, whose work provides a new perspective on plant pathology, susceptibility to soil-borne pathogens, and plant absorption of nutrients. Dr. White explains how endophytes, non-pathogenic fungal and bacterial organisms present in all plants, are a mechanism by which plants can absorb complete molecules, internalize and propagate soil-borne microbes, and nullify pathogenic organisms.
In the interview, Dr. White describes how plants cultivate microbes at the meristem, or root tip, where exudates are created. In this zone, these endophytes further attract and cultivate microbes from the soil in the rhizophagy cycle, from rhizo- meaning ‘root’ and -phagy meaning ‘eating’. Through this process, plants attract and internalize soil-borne microbes. The microbes are then internalized by the plant and deliver nutrients from the soil directly to the roots.
Dr. White relates how this endophytic process encourages oxidative interaction, fostering hardier, more stress-tolerant plants, and how nitrogen applications and fertilizer decrease the incidence of these endophytes, leading to disease-susceptible crops. In cotton culture, for example, the practice of seed de-linting prior to planting effectively destroys the endophytes present on the seed.
Besides stimulating growth and stress tolerance within the seedling by bringing nutrients from the soil, endophytes also colonize pathogenic fungi, resulting in their reduced virulence. The endophytes don’t kill the fungi, but rather they colonize and weaken it so disease incidence is greatly reduced. In some cases, those pathogenic fungi will actually become endophytic fungi in the plant, as in the example of Fusarium oxysporum. Once Fusarium oxysporum is colonized by the endophytic bacteria, it grows more slowly and onto the plant leaf surface. However, as long as the endophytic bacteria are also present, the Fusarium organism doesn’t cause disease.
Dr. White describes how researchers are just beginning to understand the significance of endophytic functions and the rhizophagy cycle. In the future, we are enabled to be more cognizant of what we're doing to the soil and plant microbiome in the process of cultivating plants.
In this absorbing conversation, John and James cover the science behind:
Research Paper: Rhizophagy Cycle: An Oxidative Process in Plants for Nutrient Extraction from Symbiotic Microbes
Research Article: Pest Management Science: Review: Endophytic microbes and their potential applications in crop management