While humanity is facing the COVID-19 pandemic, the citrus industry is trying to manage its own devastating disease, Huanglongbing (HLB), also known as citrus greening disease. HLB is the most destructive citrus disease in the world. In the past decade, the disease has annihilated the Florida citrus industry, reducing orange production for juice and other products by 72%. Candidatus Liberibacter asiaticus (CLas) is the microbe associated with the disease. It resides in the phloem of the tree and, like many plant pathogens, is transmitted by insects during feeding events. Disease progression can be slow but catastrophic. Symptoms begin with blotchy leaves, yellow shoots, and stunting, and progress into yield decline, poor quality fruit, and eventually death.
Currently, the only thing citrus growers can do to protect their crops from HLB is control the insect vector. Dozens of researchers are trying to find ways to manage the disease, using strategies ranging from pesticides to antibiotics to CLas-sniffing dogs. Understanding the plant microbiome, an exciting new frontier in plant disease management, is another strategy.
Dr. Caroline Roper and first author Dr. Nichole Ginnan at the University of California, Riverside led a large research collaboration that sought to explore the microbiome's role in HLB disease progression. Their recent article in Phytobiomes Journal, "Disease-Induced Microbial Shifts in Citrus Indicate Microbiome-Derived Responses to Huanglongbing," moves beyond the single-snapshot view of the microbial landscape typical of microbiome research. Their holistic approach to studying plant-microbe interactions captured several snapshots across three years and three distinct tissue types (roots, stems, and leaves). What is so interesting about this research is the use of amplicon (16S and ITS) sequencing to capture the highly intricate and dynamic role of the microbiome (both bacterial and fungal) as it changes over the course of HLB disease progression.