Coffee leaf rust (CLR) is a devastating fungal pathogen of coffee plants

The Synergistic Hawaii Agriculture Council received a $225,000 project grant from the National Institute of Food and Agriculture (NIFA) under the Agriculture and Food Research Initiative (AFRI) program (CFDA 10.310), awarded August 1, 2025, with completion targeted for July 31, 2027. The research project addresses Coffee Leaf Rust (CLR), a devastating fungal pathogen responsible for estimated global losses of $1-2 billion annually. The awardee will conduct DNA sequencing and greenhouse experiments to identify differences in microbial communities (fungi and bacteria) on the leaf surfaces of healthy versus CLR-infected coffee plants, examining variation across different coffee cultivars and monitoring disease progression over a four-week period. The research will also evaluate the effects of fungicide treatments and biological control methods on leaf surface microbial communities.

The project deliverables include identification of microbiological indicators associated with CLR disease progression to inform cultivar selection and pathogen management strategies. Results will be disseminated through multiple channels: direct engagement with coffee growers and farm laborers via workshops, academic communication through research articles and conference presentations, and public outreach through open-access publishing and collaboration with extension agents. These outputs are designed to support evidence-based decision-making within Hawaii's agricultural sector and contribute to broader coffee production sustainability.

When infected, coffee trees experience a reduction in photosynthesis and a loss of leaves. These symptoms can lead to reduced coffee yields, an estimated global value of $1-2 billion in losses. Due to the complex life cycle of the fungal agent responsible for CLR (hemileia vastatrix), the disease is challenging to manage when outbreaks occur and can spread rapidly. This work aims to understand whether the community of other microbes (particularly fungi and bacteria) present on the leaf surfaces of coffee can help or hinder the establishment of the fungus that causes CLR. To pursue this research, I will use DNA sequencing to identify any differences in the fungal and bacterial communities on the surfaces of healthy and CLR-infected coffee leaves. I will also investigate if different cultivars of coffee can harbor different communities of fungi and bacteria on healthy and CLR-infected leaves. Changes in these communities associated with the progression of the CLR disease will be monitored in greenhouse experiments over a 4-week period. Lastly, the effect of fungicides and biological control of CLR on the communities of leaf surface fungi and bacteria will be studied. Combined, the results of this work can lead to understanding the microbiological indicators that are associated with CLR disease. This insight can aid in the selection of cultivars grown and the pathogen management regime employed to combat CLR. Results of this work will be communicated to coffee growers and farm laborers through workshops, with the scientific community through research articles and conference presentations, and with the general public through open-access publishing and collaborating with extension agents.