Research Update: Stable Antimicrobial Peptide

Jim Rogers Peptides, Research

By Hailing Jin

Research on the effectiveness of a novel stable antimicrobial peptide (SAMP) identified from the Australian finger lime (Microcitrus australasica) to fight huanglongbing (HLB) continues in a multistate initiative involving 1,500 citrus trees. Although the pandemic has impacted the progress of the research, work has steadily continued and expanded. 

Researchers at the University of California, Riverside and University of California, Davis found that SAMP could inhibit the HLB-causing bacterium Ca. Liberibacter (CLas) strains in greenhouse settings. Three greenhouse trials using an application of SAMP on HLB-positive trees reduced the bacterial titer and inhibited the disease symptoms. Researchers also found that SAMP has an additional function: It induces the plant’s immune responses. Two greenhouse trials showed that SAMP served as a protectant on young trees to protect them from future infection. 

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Untreated citrus plants on the left compared to treated ones on the right (Photo by Hailing Jin, University of California, Riverside)

Several field trials have been underway in Florida since fall 2020 by Megan Dewdney, associate professor at the University of Florida Institute of Food and Agricultural Sciences Citrus Research and Education Center. Although the trials were slightly delayed due to the pandemic, the testing sites and number of test trees were increased in 2022.

The technology of SAMP was licensed by a biotech company, Invaio Sciences, which has made consistent and sustained effort to perform trials. The company has figured out a technique to produce SAMP on an industry scale at a low cost, which represents a big step forward to develop effective solutions for HLB control.

During 2020 and 2021, M. australasica stable antimicrobial peptide (MaSAMP) trials were used to successfully evaluate potential commercial formulations and use patterns, including application concentration, rate and timing. The 2022 field trial program includes 29 trials with at least one MaSAMP treatment on four different orange varieties.There are 18 trials in Florida, including fruit-bearing and non-bearing trees (including transplants), designed to evaluate efficacy of MaSAMP formulations and use patterns across a wide range of environmental and cultural conditions. The efficacy trials are managed by contract research organizations (CROs), the University of Florida and Invaio.

The 2022 field trial program also includes 10 experimental trials across Florida and Texas, with fruit-bearing trees and transplants, designed to better understand factors that influence MaSAMP performance in the field. These trials are managed by CROs, citrus industry collaborators, universities and Invaio. In most trials, the impact of MaSAMP on CLas, Asian citrus psyllids, disease symptoms, fruit yield, fruit drop and juice quality are evaluated. During 2022, data will be collected from approximately 1,500 orange trees. 

Researchers are working on this peptide project with full speed and will continue to inform the industry of any new progress.

Hailing Jin is a professor at the University of California, Riverside.

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