Diversity and pathogenicity of Lasiodiplodia species associated with banana crown rot in Northern and Northeastern Brazil – Nature

Report on the Diversity and Pathogenicity of Lasiodiplodia Species Associated with Banana Crown Rot in Brazil

Executive Summary

This report details a comprehensive 2023 survey identifying the fungal pathogens responsible for banana crown rot, a major postharvest disease causing substantial economic losses in Brazil. The study aligns with critical Sustainable Development Goals (SDGs), particularly SDG 2 (Zero Hunger) and SDG 12 (Responsible Consumption and Production), by addressing a key threat to food security and a driver of food loss. Through morphological and multigene phylogenetic analysis, a complex of at least six distinct Lasiodiplodia species was identified as the causal agent of the disease. Pathogenicity tests confirmed the virulence of all identified species. These findings provide a crucial foundation for developing targeted, sustainable disease management strategies to reduce food waste, enhance food security, and promote sustainable agricultural practices in line with global development objectives.

Introduction: Global Food Security and Sustainable Agriculture

The Role of Bananas in Achieving SDG 2 (Zero Hunger)

Bananas (Musa spp.) are a cornerstone of global food security, serving as the fourth most important staple food crop worldwide after rice, wheat, and maize. Cultivated in over 130 countries, they are vital for nutrition and economic stability in tropical and subtropical regions. Brazil is one of the world’s largest producers, with its northern and northeastern regions contributing significantly to national output. The stability of banana production is therefore directly linked to achieving SDG 2, which aims to end hunger, achieve food security, and promote sustainable agriculture.

The Threat of Postharvest Disease to SDG 12 (Responsible Consumption and Production)

Crown rot is the most significant postharvest disease affecting bananas, severely compromising fruit quality, limiting marketability, and leading to substantial food and economic losses. This issue directly contravenes the objectives of SDG 12, particularly Target 12.3, which calls for halving per capita global food waste at the retail and consumer levels and reducing food losses along production and supply chains. The disease, caused by a variety of fungal pathogens, creates a major bottleneck in the value chain, undermining efforts to establish responsible and sustainable consumption and production patterns.

Research Objectives for Sustainable Disease Management

A precise understanding of the etiological agents of crown rot is fundamental for developing effective and sustainable management strategies. Such strategies are essential for protecting terrestrial ecosystems, as outlined in SDG 15 (Life on Land), by reducing reliance on broad-spectrum chemical fungicides. This study aimed to conduct the first large-scale survey to characterize the Lasiodiplodia species associated with banana crown rot in key production areas of North and Northeastern Brazil using morphological, pathogenic, and molecular data.

Methodological Framework

Sample Collection and Fungal Isolation

Banana fruit samples were collected from commercial plantations across 34 municipalities in ten states of Northern and Northeastern Brazil. A total of 116 fungal isolates exhibiting morphological traits consistent with the genus Lasiodiplodia were recovered from fruits showing symptoms of crown rot. The isolates were purified and deposited in the phytopathogenic fungal Culture Collection of the Federal University of Alagoas (COUFAL) for further analysis.

Pathogen Identification: A Polyphasic Approach

A polyphasic strategy combining classical and molecular techniques was employed for accurate species identification, a crucial step for developing targeted interventions that support SDG 12.

• Morphological Analysis: Colony and conidial characteristics were observed and measured to provide a baseline for identification.
• Multigene Phylogenetic Analysis: To resolve cryptic species and ensure precise identification, DNA was extracted from isolates and four genomic regions were sequenced:
  1. Internal transcribed spacer (ITS)
  2. Translation elongation factor 1-alpha (tef1-α)
  3. β-tubulin (tub2)
  4. RNA polymerase II subunit (rpb2)

Pathogenicity and Aggressiveness Assessment

To confirm the role of the identified fungi as causal agents of crown rot, pathogenicity tests were conducted. Mycelial plugs of representative isolates were used to inoculate wounded banana fruits of three cultivars: ‘Prata’, ‘Pacovan’, and ‘Terra’. The development of disease symptoms was monitored, and the fungi were re-isolated from symptomatic tissues to fulfill Koch’s postulates. This step is vital for confirming the direct threat these pathogens pose to food production systems, impacting SDG 2.

Key Findings and Implications for Sustainable Development

Identification of a Pathogen Complex

Multilocus phylogenetic analysis of the concatenated dataset (ITS, tef1-α, tub2, and rpb2) revealed that banana crown rot in Brazil is not caused by a single species but by a complex of at least six phylogenetically distinct Lasiodiplodia species. This finding complicates disease management and underscores the need for robust, integrated strategies to protect this vital food resource.

1. Lasiodiplodia brasiliensis
2. Lasiodiplodia hormozganensis
3. Lasiodiplodia iraniensis
4. Lasiodiplodia laeliocattleyae
5. Lasiodiplodia pseudotheobromae (First report on bananas in Brazil)
6. Lasiodiplodia theobromae

L. theobromae was the most prevalent species across the surveyed regions, although its distribution varied. The discovery of this species complex highlights a significant challenge to ensuring resilient and sustainable agriculture under SDG 2.

Pathogenicity Confirmation and Virulence

All six identified Lasiodiplodia species were confirmed to be pathogenic on the three tested banana cultivars, inducing typical crown rot symptoms such as necrotic lesions and pulp softening. This confirmation directly links the pathogen complex to postharvest losses that undermine SDG 12. Significant differences in aggressiveness were observed:

• L. pseudotheobromae and L. hormozganensis were among the most aggressive species, causing the largest lesions on ‘Pacovan’ and ‘Prata’ cultivars.
• Intraspecific variation in aggressiveness was also noted, particularly within L. theobromae isolates.

This variability in virulence suggests that management strategies must be robust enough to handle a diverse and dynamic pathogen population.

Conclusion: Aligning Disease Management with Sustainable Development Goals

This study provides the first systematic identification of the Lasiodiplodia species complex causing banana crown rot in Brazil, revealing a greater diversity of pathogens than previously known. This research is a critical step toward mitigating a major threat to a globally important food crop and aligns directly with several SDGs.

• Contribution to SDG 2 (Zero Hunger): By identifying the specific causal agents of a disease that threatens a staple food source, this work provides the foundational knowledge needed to protect crop yields, stabilize farmer incomes, and enhance food security.
• Advancing SDG 12 (Responsible Consumption and Production): The detailed characterization of the pathogen complex enables the development of targeted, integrated pest management (IPM) strategies. Such strategies can significantly reduce postharvest losses, thereby reducing food waste and minimizing the need for broad-spectrum chemical fungicides, promoting more sustainable production systems.
• Supporting SDG 15 (Life on Land): A precise understanding of the pathosystem allows for more targeted interventions, reducing the environmental impact of disease control measures and helping to conserve biodiversity within agricultural ecosystems.

The identification of six pathogenic species, including the first report of L. pseudotheobromae on bananas in Brazil, underscores the urgent need for ongoing surveillance and research. Future efforts should focus on the epidemiology of these species and the development of innovative, non-chemical control methods to build a more resilient and sustainable banana production system for the future.

Analysis of Sustainable Development Goals (SDGs) in the Article

1. Which SDGs are addressed or connected to the issues highlighted in the article?

The article on banana crown rot disease connects to several Sustainable Development Goals (SDGs) due to its focus on agriculture, food security, economic stability, and environmental factors.

• SDG 2: Zero Hunger

  This is the most directly relevant SDG. The article highlights that bananas are the “fourth most important staple food crop in the world” and a primary food source in over 130 countries. The crown rot disease causes “substantial economic losses by compromising fruit quality and limiting marketability,” which directly threatens food availability and security. The study’s ultimate goal is to inform “effective and sustainable disease management strategies,” which is crucial for protecting this vital food source and ending hunger.

• SDG 12: Responsible Consumption and Production

  The article focuses on “crown rot,” which it identifies as a “major postharvest disease.” Post-harvest losses are a critical issue in sustainable food systems. By investigating the causes of this disease, the research directly contributes to understanding and potentially reducing food losses that occur between harvest and consumption, aligning with the goal of ensuring sustainable consumption and production patterns.

• SDG 13: Climate Action

  The article establishes a connection between the fungal pathogens and climate conditions. In the discussion, it notes that “temperature is a key factor in Lasiodiplodia pathogenicity, particularly under projected climate change scenarios.” The research on the optimal growth temperatures of the fungi suggests that rising global temperatures could exacerbate the disease’s impact. This links the agricultural problem to the broader challenge of climate change and the need to build resilience in food systems.

2. What specific targets under those SDGs can be identified based on the article’s content?

Based on the issues discussed, several specific SDG targets can be identified:

1. SDG 2: Zero Hunger

   • Target 2.1: By 2030, end hunger and ensure access by all people, in particular the poor and people in vulnerable situations, including infants, to safe, nutritious and sufficient food all year round. The article addresses this by focusing on a disease that threatens a staple food crop, thereby impacting the sufficiency and availability of food.
   • Target 2.3: By 2030, double the agricultural productivity and incomes of small-scale food producers… The disease causes “substantial economic losses,” directly impacting the productivity and income of farmers in Brazil and other banana-producing nations. Managing the disease would help achieve this target.
   • Target 2.4: By 2030, ensure sustainable food production systems and implement resilient agricultural practices that increase productivity and production… The study’s stated aim to contribute to “effective and sustainable disease management strategies” is in perfect alignment with this target.

2. SDG 12: Responsible Consumption and Production

   • Target 12.3: By 2030, halve per capita global food waste at the retail and consumer levels and reduce food losses along production and supply chains, including post-harvest losses. The article’s entire focus is on a “major postharvest disease,” which is a primary driver of post-harvest food loss in the banana supply chain. Understanding the pathogens is the first step toward reducing these losses.

3. SDG 13: Climate Action

   • Target 13.1: Strengthen resilience and adaptive capacity to climate-related hazards and natural disasters in all countries. The article’s finding that higher temperatures may increase pathogen virulence highlights how climate change is a hazard to agriculture. Research into the pathogen’s response to temperature is essential for developing adaptive strategies to protect crops in a warming world.

3. Are there any indicators mentioned or implied in the article that can be used to measure progress towards the identified targets?

The article does not explicitly mention SDG indicators, but it contains data and discusses concepts that serve as or contribute to them:

• Implied Indicator for Target 12.3 (Food Loss)

  The article’s focus on “postharvest disease” and “substantial economic losses” directly relates to Indicator 12.3.1: (a) Food loss index. While the study does not calculate this index, its investigation into the causes of fruit loss provides the foundational scientific data needed to develop strategies that would reduce the food loss index for bananas.

• Proxy Indicators for Disease Severity and Impact

  The study uses specific, measurable data points that act as proxies for assessing the problem and measuring the effectiveness of future interventions:

  • Lesion Diameter (mm): In the pathogenicity tests, researchers measured the “lesion diameter (mm)” on inoculated fruits. This is a direct, quantifiable indicator of disease severity and aggressiveness, which correlates with the extent of food quality degradation and potential loss.
  • Mycelial Growth Rates at Different Temperatures: The experiment measuring the “optimal growth temperatures” of the fungi provides a clear indicator of how environmental conditions, linked to climate change, affect the pathogen. This data can be used to model future disease risk under different climate scenarios, contributing to resilience planning (Target 13.1).

4. Table of Findings

Source: nature.com