Florida-based scientists published an article in Microorganisms indicating citrus-derived endophytes have potential for managing HLB. Endophytes are endosymbionts, often bacteria or fungi, which live within a plant for at least part of its life cycle without causing apparent disease.
The authors of the article are Jessica Dominguez, Krishnaswamy Jayachandran and Kateel G. Shetty of Florida International University, and U.S. Department of Agriculture-Agricultural Research Service scientists Joseph Krystel and Ed Stover (retired). Edited excerpts follow:
Huanglongbing (HLB), also known as citrus greening, is an insidious disease that has become a threat to the sustainability of the citrus industry worldwide. In the United States, Candidatus Liberibacter asiaticus (CLas) is the pathogen that is associated with HLB.
Current HLB control methods are primarily based on the use of insecticides and antibiotics, where effectiveness is limited and may have negative impacts on beneficial and non-target organisms. Thus, there is an urgent need for the development of effective and sustainable treatment options to reduce or eliminate CLas from infected trees.
In this study, citrus-derived endophytes, their cell-free culture supernatants (CFCS) and crude plant extracts were screened for antimicrobial activity against two culturable surrogates of CLas, Sinorhizobium meliloti and Liberibacter crescens. Candidates considered high-potential antimicrobial agents were assessed directly against CLas in vitro. As compared to the negative controls, statistically significant reductions of viable CLas cells were observed for each of the five bacterial CFCS.
Gene sequencing revealed that each of the five bacterial isolates were most closely related to Bacillus amyloliquefaciens, a species dominating the market of biological control products. As such, the aboveground endosphere of asymptomatic survivor citrus trees, grown in an organic orchard, were found to host bacterial endophytes capable of effectively disrupting CLas cell membranes. These results concur with the theory that native members of the citrus microbiome play a role in the development of HLB. Five strains of B. amyloliquefaciens were identified that demonstrate notable potential to be used as sources of novel antimicrobials for the sustainable management of HLB.
While these results are promising, they entail the need for further exploration. These naturally derived anti-CLas agents hold significant potential for HLB management, potentially increasing yield and productivity while reducing environmental impacts.
The full scientific article about this study can be found here.
Sources: MDPI
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