Witches' broom disease, caused by the fungus Moniliophthora perniciosa, decimated cocoa crops in southern Bahia state, Brazil, in the 1990s. It was even the subject of a local soap opera and continues to plague the chocolate industry in the Amazon region. However, a recent study published in Scientific Reports offers hope that increased cocoa production in the Amazon region will not rely so heavily on fungicides and fertilizers.
Supported by FAPESP and conducted at the Frederico Afonso Experimental Station (CEPLAC) in Rondônia state, the study evaluated 25 cocoa cultivars and identified two with superior performance. Both demonstrated a greater ability to maintain high productivity in mineral-poor soils and when attacked by the witches' broom fungus, known in the region as "lagartão." Production increased by up to 32% compared to more susceptible varieties.
The research project involved collaboration between scientists at São Paulo State University (UNESP), the Brazilian Agricultural Research Corporation (EMBRAPA) in Porto Velho, the Federal University of Rondônia (UNIR, Rolim de Moura campus), and the Federal University of Amazonas (UFAM, Humaitá campus).
"The study demonstrates, in practice, that combining genetic improvement and nutritional management is the most sustainable and long-term strategy for cocoa production. Since it isn't possible to modify the environment [the hot and humid climate of the Amazon favors the activity of the fungus], the solution is to plant varieties with high adaptability, strengthened by nutrition that ensures plant vigor and resistance," says Renato de Mello Prado , a professor at the Faculty of Agricultural and Veterinary Sciences (FCAV) at UNESP in Jaboticabal, who coordinated the research.
The study found that clones EEOP 63 and EEOP 65 stood out for their combination of high seed productivity, better nutritional balance, and greater tolerance to witches' broom under Amazonian climatic conditions.
The researchers emphasize the need for similar and broader studies in the Amazon region to develop new clones with all three characteristics: high nutritional efficiency, high productivity, and disease resistance. "This is important because only then will farmers have different clone options to grow on their properties. The study reinforces the idea that clone diversity on the farm is an essential strategy for addressing the current challenges of cocoa cultivation in a sustainable manner," says Prado.
Both cacao and the witches' broom fungus are native to the Amazon region. It is in the characteristic climate of the forest – with intense rainfall, high heat, and humidity – that the fungus finds ideal conditions to thrive. Additionally, in some areas of the region, the soil has a mineral imbalance, becoming acidic with low base saturation, which affects plant performance.
"The study confirms that tolerance to witches' broom in the Amazon isn't an isolated trait but rather can be modulated by the nutritional balance and productive capacity under stress of a cultivar," says Edilaine Istéfani Franklin Traspadini , a FAPESP postdoctoral fellowship recipient .
The two selected clones differ in the quality of their mineral profiles, particularly in their high concentrations of phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg).
"When attacked, the plant faces a dilemma: whether to invest energy in growth or in resistance. But if the plant receives adequate nutrition and has the right genetics, it can do both at the same time. With balanced genetics and nutrition, the plant overcomes this limitation," says Prado.
More balance, fewer pesticides
Another interesting aspect relates to the natural state of Amazonian soils. In the study, the researchers analyzed the balance of 17 nutrients in soil samples. They identified a boron deficiency and excess nitrogen in most samples and found that nutritional balance reduces the vulnerability of plants to witches' broom and ensures that plants maintain their productive capacity even under stress.
Traspadini points out that Amazonian soils are highly weathered and naturally poor in micronutrients. "Nutritional balance strengthens the plant's defense system, allowing growth and resistance to occur simultaneously without excessive reliance on agrochemicals," he explains.
The nutritional aspect directly impacts the plant. "We observed a consistent deficiency trend in these elements in the evaluated clones, especially in boron, which is essential for cell wall integrity and reproductive processes such as pollen tube growth and fruit set. This reinforces the importance of balanced fertilization that also pays attention to micronutrients, which are often neglected, to sustain plant productivity and resistance," says Traspadini.
Meanwhile, the accumulation of unmetabolized nitrogen generates compounds that serve as food for the fungus.
For Prado, the major distinction of the study lies in its integration of genetic improvement and nutritional data for the first time. "Tackling the disease requires a multidisciplinary approach because the plant's defense system is both genetic and nutritional. This is the cheapest, most sustainable, and most efficient way to limit production losses caused by witches' broom," she concludes.
About São Paulo Research Foundation (FAPESP)
The São Paulo Research Foundation (FAPESP) is a public institution with the mission of supporting scientific research in all fields of knowledge by awarding scholarships, fellowships and grants to investigators linked with higher education and research institutions in the State of São Paulo, Brazil. FAPESP is aware that the very best research can only be done by working with the best researchers internationally. Therefore, it has established partnerships with funding agencies, higher education, private companies, and research organizations in other countries known for the quality of their research and has been encouraging scientists funded by its grants to further develop their international collaboration. You can learn more about FAPESP at www.fapesp.br/en and visit FAPESP news agency at www.agencia.fapesp.br/en to keep updated with the latest scientific breakthroughs FAPESP helps achieve through its many programs, awards and research centers. You may also subscribe to FAPESP news agency at http://agencia.fapesp.br/subscribe.
