Cacao biotechnology and biological control

Three lines of work aim to change how cacao is bred, multiplied and protected: editing its genes, cloning it from tissue culture, and recruiting the fungi and bacteria that already live inside it. Each has published results. Almost all of them stop at the laboratory door.

5 studies2022 to 2026Each checked against its published abstract

What these studies add up to

Gene editing of cacao has moved from possibility to plants. One study produced edited trees carrying no inserted DNA, with lesions from the black pod pathogen 42% smaller in a challenge test, and reports field trials under way. No field result has been read.
The tools work: inserted marker genes were inherited by seed in the proportions inheritance predicts, in two cultivars.
Cloning cacao from tissue culture is held back by embryos that form abnormally and do not germinate. One study ties the abnormal ones to differences in DNA methylation; none read here offers a cure.
Fungi and bacteria isolated from inside cacao suppress the frosty pod rot fungus on laboratory plates. Neither study here treated a tree.
Prediction of disease resistance from genome-wide markers, summarised in the genetics area, is the nearest of these approaches to routine use in breeding.

Why cloned cacao embryos often fail: abnormal ones carry different DNA methylation

Garcia and colleagues, 2022. Scientific reports. doi:10.1038/s41598-022-18035-9

Question: What distinguishes the abnormal somatic embryos that hamper tissue-culture propagation of cacao from normal ones?
How: Whole-genome bisulfite sequencing of zygotic embryos, normal somatic embryos and abnormal somatic embryos of Theobroma cacao, comparing methylation gene by gene.
Finding: The authors identified 873 genes methylated differently between the three kinds of embryo, with roles in development, programmed cell death, oxidative stress and hypoxia. They propose that ethylene and its precursor are involved in the abnormalities. The abstract states that many morphologically abnormal somatic embryos that do not germinate are frequently observed, hampering plant production on a commercial scale.

Does not establish: It does not show how to prevent abnormal embryos, or how trees raised from somatic embryos perform in the field.

Limits: An association between methylation and abnormality, with a hypothesis about cause. The abstract gives no rate of abnormal embryos and tests no remedy.

On this site: Cacao genetics: the studies

Volatiles from bacteria living in cacao inhibited the frosty pod rot fungus in vitro

De la Cruz-López and colleagues, 2022. Current microbiology. doi:10.1007/s00284-021-02696-2

Question: Which volatile compounds do endophytic bacteria from cacao produce, and do they inhibit Moniliophthora roreri?
How: Volatiles from six endophytic bacterial strains (five Bacillus and one Novosphingobium) collected and identified by SPME and GC-MS, and tested against mycelium growth and spore germination of M. roreri, alongside five synthetic volatile compounds alone and in mixtures.
Finding: Volatiles from three of the strains inhibited mycelium growth by more than 35%, sporulation by more than 81% and spore germination by more than 74%. Of the synthetic compounds, 2-ethyl hexanol at 100,000 ppm inhibited mycelium growth by 100%.

Does not establish: It does not show that these bacteria or their volatiles control frosty pod rot on a tree.

Limits: Laboratory assays in closed dishes, with synthetic compounds at very high concentration. Nothing was tested on a plant.

On this site: Frosty pod rot

Gene-edited cacao without the transgene: smaller black pod lesions in a leaf test

Guiltinan and colleagues, 2026. Plant biotechnology journal. doi:10.1111/pbi.70365

Question: Can editing a cacao gene that restrains the plant's own defences reduce susceptibility to Phytophthora, and can the edit be kept while the inserted editing machinery is bred out?
How: CRISPR-Cas9 editing of the TcNPR3 gene. Edited first-generation plants were grown to maturity and crossed with unmodified cacao; the parents and 22 progeny were whole-genome sequenced, gene expression was analysed, and susceptibility was tested by challenging tissue with Phytophthora. The first-generation lines were tested in in vitro foliar assays.
Finding: Seven progeny kept the edited alleles and carried no inserted DNA. Genome-edited plants looked comparable to unmodified controls and showed a 42% reduction in lesion size when challenged with Phytophthora. The authors report that field trials are under way.

Does not establish: It does not show that an edited tree loses fewer pods to black pod on a farm, that the effect lasts, or that such trees could legally be planted or their cocoa sold anywhere.

Limits: Susceptibility was measured as lesion size in a challenge test, not as pods lost in a field. The abstract reports no yield, no flavour and no result from the field trials. A published correction to the paper exists and was not read.

On this site: Black pod · Cacao pests and diseases: the studies

Inserted genes passed to the next generation of cacao as inheritance predicts

Austin and colleagues, 2026. Plants (Basel, Switzerland). doi:10.3390/plants15040642

Question: Does a transformation method for cacao work in elite cultivars, and are the inserted genes inherited stably by seed?
How: Agrobacterium-mediated transformation of explants from secondary somatic embryos of two cultivars, INIAPG-038 and Matina 1-6, with three vectors carrying a yellow fluorescent marker gene and a selection gene. Three events in one cultivar and one in the other were crossed, and the progeny were scored for the marker and the transgene.
Finding: The plants produced fertile seed. The marker segregated 1:1 when a transgenic plant was crossed with an unmodified one and 3:1 when transgenic plants were crossed with each other, whichever parent supplied the pollen. The transgenic plants had a normal phenotype and their seeds germinated at 97%.

Does not establish: It shows that the tool works, not that any useful trait has been added to cacao by it.

Limits: The inserted genes were markers with no agronomic purpose. Four events in two cultivars were followed. The abstract does not state who funded the work.

On this site: Cacao genetics: the studies

Trichoderma living inside Peruvian cacao suppressed frosty pod rot in the laboratory

Santillan-Culquimboz and colleagues, 2026. Frontiers in microbiology. doi:10.3389/fmicb.2026.1811538

Question: Which Trichoderma species live as endophytes in Peruvian cacao, and do they antagonise Moniliophthora roreri and Fusarium?
How: Endophytic Trichoderma isolated from cacao in Peru, identified by three gene regions and by morphology, and tested in vitro for antibiosis, mycoparasitism and antagonism against the two pathogens.
Finding: Six named species were identified, two reported from cacao for the first time, and several isolates fitted no known species. In the laboratory assays the strains showed antagonism of approximately 80% against M. roreri and approximately 70% against Fusarium.

Does not establish: It does not show that applying any of these fungi protects a cacao crop. Laboratory antagonism has often failed to carry over to the field.

Limits: Every result is from a laboratory plate. No tree, pod or field was treated.

On this site: Frosty pod rot · Cacao pests and diseases: the studies

What is still open

Whether an edited tree loses fewer pods in a field, over years, and what it yields.
How any producing or importing country would regulate gene-edited cacao. No regulatory text was read.
How trees raised from somatic embryos perform on farms compared with grafted or seedling trees.
Whether any endophyte that works on a plate protects pods on a tree. Field trials of biological control are summarised in the pests and diseases area.
Reviews of each field. The five studies here are individual papers chosen from searches of titles, not a systematic sample.

These are questions the studies read for this page leave unanswered. They are not a claim that nobody has answered them.

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