(2026-02-02 02:39:00) – Antananarivo, Madagascar
A recent outbreak of bacterial leaf blight (BLB) in Madagascar originated from a single introduction of the disease from Asia, most likely India, according to new research that identifies potential resistance genes for rice farmers.
- Bacterial leaf blight (BLB), a devastating rice disease, was detected in Madagascar for the first time in 2019.
- Researchers found the Malagasy strains of the disease are closely related to those found in India, suggesting a recent introduction from Asia.
- the study identified four resistance genes – Xa8, Xa13, Xa21, adn Xa23 – that could be used to protect Malagasy rice crops.
A new study has traced the origin of a recent bacterial leaf blight (BLB) outbreak in Madagascar to Asia, offering crucial insights for disease control and safeguarding the nation’s food security.The research, based on analysis of 73 Xanthomonas oryzae pv. oryzae (Xoo) strains collected between 2019 and 2023, indicates the disease was introduced to Madagascar relatively recently.
BLB, caused by the bacterium Xoo, is a major threat to rice production, capable of causing yield losses of up to 70% in Asia and West Africa. First described in Japan in 1884, the disease spread to West Africa in the 1970s and more recently emerged in east Africa, with an epidemic reported in Tanzania in 2019. The simultaneous detection of BLB in Madagascar in 2019 raised concerns about its potential impact on the island nation’s rice crops.
Identifying the Source and Vulnerabilities
Table of Contents
Researchers used MLVA genotyping,which revealed a low diversity of strains,forming a single clonal complex. This suggests a single, recent introduction of the disease. Further analysis, including whole-genome sequencing, showed that the Malagasy strains are most closely related to those originating from India, according to the study. Notably, the Malagasy strains did not cluster with recently reported Xoo strains from Tanzania, indicating independent introductions of the disease to the two East African nations.
The study also identified a key vulnerability in Malagasy rice varieties. researchers found that all 19 Malagasy rice varieties assessed were susceptible to the BLB strains.Analysis of SWEET knock-out lines confirmed that the Malagasy strains rely on the susceptibility gene OsSWEET11 for full virulence, and identified a PthXo1 ortholog predicted to induce OsSWEET11.
Potential for Resistance
Importantly, the research identified four resistance genes – Xa8, Xa13, Xa21, and Xa23 – that confer resistance to all Malagasy strains tested. This finding offers a pathway for developing disease-resistant rice varieties tailored to the specific strains circulating in Madagascar.
Why It Matters
The rapid spread of BLB poses a significant threat to global food security, especially in regions heavily reliant on rice as a staple crop. This study’s pinpointing of the origin of the outbreak in Madagascar, and the identification of effective resistance genes, is a critical step toward mitigating the disease’s impact. The findings allow for targeted breeding programs and deployment of resistant varieties, potentially preventing widespread crop losses and protecting the livelihoods of Malagasy rice farmers. The research underscores the importance of ongoing surveillance and rapid response to emerging plant diseases to safeguard food supplies.
time.news based this report on research findings published in [source article] and added independent analysis and context.
