An integrated approach to improve plant protection against olive anthracnose caused by the Colletotrichum acutatum species complex

Abstract

The olive tree (Olea europaea L.) is the most important oil-producing crop of the Mediterranean basin. However, although plant protection measures are regularly applied, disease outbreaks represent an obstacle towards the further development of the sector. Therefore, there is an urge for the improvement of plant protection strategies based on information acquired by the implementation of advanced methodologies. Recently, heavy fungal infections of olive fruits have been recorded in major olive-producing areas of Greece causing devastating yield losses. Thus, initially, we have undertaken the task to identify their causal agent(s) and assess their pathogenicity and sensitivity to fungicides. The disease was identified as the olive anthracnose, and although Colletotrichum gloeosporioides and Colletotrichum acutatum species complexes are the two major causes, the obtained results confirmed that in Southern Greece the latter is the main causal agent. The obtained isolates were grouped into eight morphotypes based on their phenotypes, which differ in their sensitivities to fungicides and pathogenicity. The triazoles difenoconazole and tebuconazole were more toxic than the strobilurins being tested. Furthermore, a GC/EI/MS metabolomics model was developed for the robust chemotaxonomy of the isolates and the dissection of differences between their endo-metabolomes, which could explain the obtained phenotypes. The corresponding metabolites-biomarkers for the discrimination between morphotypes were discovered, with the most important ones being the amino acids L-tyrosine, Lphenylalanine, and L-proline, the disaccharide α,α-trehalose, and the phytotoxic pathogenesis-related metabolite hydroxyphenylacetate. These metabolites play important roles in fungal metabolism, pathogenesis, and stress responses. The study adds critical information that could be further exploited to combat olive anthracnose through its monitoring and the design of improved, customized plant protection strategies. Also, results suggest the

Olive Oils from Fruits Infected with Different Anthracnose Pathogens Show Sensory Defects Earlier Than Chemical Degradation

“…Olive anthracnose, caused by diverse Colletotrichum species, is the most important fungal disease of olive fruits worldwide, leading to significant yield losses, fruit rot and drop and consequently poor olive oil quality. In the last decade, the recrudescence of olive anthracnose epidemics has been attributed in part to climate change related to increased relative humidity and rain levels in autumn and abnormal temperature fluctuations [1,2]. In addition to environmental conditions, the susceptibility of varieties and the virulence of the pathogen populations are decisive for the occurrence of epidemics [3][4][5].…”

Synthesis and Characterization of Novel Copper Nanoparticles for the Control of Leaf Spot and Anthracnose Diseases of Olive

“…Currently, 13 different Colletotrichum species are associated to anthracnose of olive, among which six species belong to the C. acutatum species complex and two species belong to the C. gloeosporioides species complex [ 18 , 19 ]. In Greece, although the disease is known since 1920, its precise etiology only recently was elucidated, suggesting that the C. acutatum species complex is the predominant disease agent [ 20 ]. The most destructive disease symptoms occur most often on mature fruit in the form of brown-dark sunken rotten lesions that under moist conditions are covered by orange conidium masses [ 21 ].…”

Discovering the Next-Generation Plant Protection Products: A Proof-of-Concept via the Isolation and Bioactivity Assessment of the Olive Tree Endophyte Bacillus sp. PTA13 Lipopeptides

“…Such results are in complete alignment with previous reports on the antimicrobial activity of Bacillus metabolites [51], confirming the bioactivity of the total LP extract of Bacillus sp. PTA13 against the olive tree phytopathogen, including the isolate with proven resistance to commercial fungicides applied in olive tree plant protection [34]. The surfactin fraction exhibited toxicity to the PLS…”

“…For the long-term maintenance of the EMs, 5-mm-diameter mycelial plugs or bacterial suspensions from freshly prepared cultures were transferred to 1.5 mL Eppendorf tubes containing glycerol:phosphate-buffered saline (PBS) (1:1, v/v) and stored at −80 • C. The bioactivity of the obtained EM isolates against C. acutatum was assessed by performing the plate confrontation assay [60]. As the target species, the C. acutatum strains PLS 88 and PLS 90 were used, the former exhibiting resistance to fungicides and the latter being sensitive [34]. Because of the slow growth rate of C. acutatum, the pathogen was initially inoculated by transferring a 5-mm-diameter mycelial plug from the edges of a 14-day old culture to the center of PDA plates.…”

“…Based on the aforementioned, as a proof of concept, EMs were isolated from tissues of olive trees (Olea europaea L. cv. Koroneiki), and the bioactivity of the microorganisms per se or their bioactive metabolites were assessed against isolates of the olive tree pathogenic fungus Colletotrichum acutatum species complex [34]. The pathogen causes olive anthracnose, one of the most devastating diseases of olive trees, resulting in heavy qualitative and quantitative yield losses.…”