Imaging sugar beet disease: MRI and PET reveal hidden damage from SBR

The study demonstrates that SBR reduces taproot growth and causes sectorial blockages in the flow of newly fixed sugars, offering early warning signs of crop decline.

Sugar beet is a cornerstone of Europe’s sugar economy, yet the fast-spreading SBR disease has emerged as a major threat. Transmitted mainly by the planthopper Pentastiridius leporinus, the proteobacterium ‘Candidatus Arsenophonus phytopathogenicus’ and the phytoplasma ‘Candidatus Phytoplasma solani’ cause severe above- and below-ground symptoms. Plants display chlorosis in leaves, narrowing of shoots, and, most critically, brown vascular discoloration in the taproot. These changes reduce taproot biomass by up to 29% and lower sugar content from around 18% to 13%, undermining both farmer income and industrial processing. Alarmingly, the pathogens have also been detected in potatoes and onions, suggesting a widening host range. Current management relies on vector control and agronomic measures, but no reliable solutions exist. Understanding how SBR alters sugar beet physiology at the organ level is essential to develop resistant varieties and integrated strategies.

A study (DOI: 10.1016/j.plaphe.2025.100053) published in Plant Phenomics on 15 May 2025 by Gregor Huber’s team, Institute for Bio- and Geosciences, could support the development of new disease management and breeding strategies to safeguard sugar production.

In this study, researchers combined molecular diagnostics with advanced imaging to investigate how SBR disrupts sugar beet taproot development over time. Quantitative PCR confirmed the presence of ‘Candidatus Arsenophonus phytopathogenicus’ in eight of ten inoculated plants, with diseased samples displaying characteristic brown discoloration in vascular tissues at harvest, while controls—including non-inoculated and qPCR-negative plants—showed no such symptoms. At harvest, infected taproots were notably smaller and lighter, with average fresh weight reduced from 43.6 ± 1.3 g in controls to 33.6 ± 2.1 g in diseased plants, and diameter shrinking from 29.6 ± 0.5 mm to 25.7 ± 0.8 mm. To capture disease progression non-invasively, magnetic resonance imaging (MRI) was conducted weekly from 21 to 63 days after inoculation, revealing progressive reductions in taproot volume (12–26% lower than controls) and narrowing of inner cambium ring widths (16–24% lower), alongside deformed ring structures and irregular tissue patterns that matched discolored vascular sectors observed destructively at harvest. Complementary positron emission tomography (PET), using radioactive carbon-11, tracked the allocation of recently fixed sugars within the developing taproot. Whereas healthy plants showed homogeneous tracer distribution, diseased plants displayed striking sectorial patterns, with entire regions devoid of tracer signal from 42 days onward, and tracer heterogeneity increasing nearly threefold by the end of the experiment. These disrupted sugar flows correlated with symptomatic tissue, reflecting localized pathogen spread through the vascular system and progressive blockages that worsened over time. By co-registering MRI and PET scans, the team achieved simultaneous structural and functional insight, demonstrating that SBR reduces biomass, alters vascular anatomy, and impairs sugar allocation at early developmental stages. This approach provides the first in-vivo visualization of a biotic stressor’s impact on sugar beet taproots, offering a detailed temporal-spatial view of disease progression.

These results carry significant implications for agriculture and food security. First, non-invasive imaging provides a powerful tool for early detection of SBR damage before symptoms are visible externally. This could help farmers and breeders screen sugar beet genotypes for susceptibility or tolerance, accelerating breeding programs for resistant varieties. Second, a better mechanistic understanding of how pathogens disrupt phloem transport and taproot development will aid in designing targeted interventions, from improved vector control to optimized crop management practices.

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References

DOI

10.1016/j.plaphe.2025.100053

Original URL

https://doi.org/10.1016/j.plaphe.2025.100053

Funding information

This study was funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany's Excellence Strategy - EXC 2070–390732324.

About Plant Phenomics

Plant Phenomics is dedicated to publishing novel research that will advance all aspects of plant phenotyping from the cell to the plant population levels using innovative combinations of sensor systems and data analytics. Plant Phenomics aims also to connect phenomics to other science domains, such as genomics, genetics, physiology, molecular biology, bioinformatics, statistics, mathematics, and computer sciences. Plant Phenomics should thus contribute to advance plant sciences and agriculture/forestry/horticulture by addressing key scientific challenges in the area of plant phenomics.