Researchers investigate use of microorganisms to mitigate abiotic stress in papaya and chili cultivation

The Faculty of Biological and Agricultural Sciences (FCBA) of the University of Colima, Tecoman campus, is working with the universities of Warwick (United Kingdom) and Ulm (Germany) on the "Development of beneficial microbial communities to mitigate abiotic stress in papaya (Carica papaya) and habanero pepper (Capsicum annuum)" project. The researchers are investigating the role of the native microbiome of the rhizosphere (the area of soil near plant roots where microbial life develops) in papaya and chili crops in order to mitigate the effects of drought and heat derived from climate change.

Wilberth Chan Cupul, the technical manager of the project for the Mexican research group, said that they had found microscopic soil fungi, bacteria, and beneficial mycorrhizal fungi associated with the papaya's rhizosphere.

“In our study, we have focused on two species, Beauveria brongniartii and Purpureocillium lilacinum. After being isolated from the rhizosphere of a papaya plantation in the municipality of Tecoman and identified morphologically and molecularly, we found that they have three types of life. They are saprobes (i.e. they live in organic matter), entomopathogens (they are parasites of insects or nematodes), and endophytes (they can live inside the papaya plant without harming it),” he said.

“They have the biochemical ability to produce indole-3-acetic acid, a phytohormone that promotes root growth and thus greater anchorage and nutrient absorption. Both fungi also have the ability to solubilize inorganic sources of phosphorus, such as tricalcium phosphate, iron phosphate, and aluminum phosphate because they produce organic acids (citric, dipicolinic, and gluconic, among others). That can slightly lower the pH of the soil and release the phosphorus from the molecules that are not assimilated by the roots of papaya or chili.”

They have also experimented with habanero pepper subjecting it to water stress. “The results indicate that, by reducing the chili crop's water by 50 and 75% and inoculating both fungi, the plant can still produce as much as if it had received 100% of the water. In other words, irrigation can be more efficiently used by applying these microorganisms. Now we need to find out what mechanisms the plants have to defend themselves against drought with the application of microorganisms,” he said.