Citrus Stubborn Severity Is Associated with Spiroplasma citri Titer But Not with Bacterial Genotype
Alexandre F S Mello1, Raymond K Yokomi2, Ulrich Melcher3
1Oklahoma State University, Department of Entomology and Plant Pathology, Stillwater 74078.
Plant Disease
|February 14, 2019
Summary
Citrus stubborn disease severity is linked to Spiroplasma citri bacterial levels, not distinct genotypes. Higher Spiroplasma citri titers in fruit correlate with more severe symptoms in citrus trees.
Area of Science:
- Plant Pathology
- Bacteriology
- Agricultural Science
Background:
- Citrus stubborn disease, caused by Spiroplasma citri, significantly impacts citrus production.
- The relationship between Spiroplasma citri bacterial levels, genetic variations, and disease symptom severity remains unclear.
Purpose of the Study:
- To investigate the association between Spiroplasma citri genotypes, bacterial titers, and the severity of citrus stubborn disease symptoms.
- To determine if bacterial levels or genetic differences in Spiroplasma citri are responsible for varying disease impacts.
Main Methods:
- Cultivation and genetic fingerprinting (RAPD and SSR) of 58 Spiroplasma citri isolates from symptomatic citrus trees.
- Analysis of the pathogenicity-related fructose operon.
- Quantitative PCR to determine Spiroplasma citri titers in fruit from mildly and severely affected trees.
Main Results:
- Four major Spiroplasma citri genotypes were identified, present in both mildly and severely symptomatic trees.
- No significant genetic variation was found in the fructose operon related to symptom severity.
- Bacterial titers were over 6,000 times higher in fruit from severely symptomatic trees compared to mildly symptomatic ones.
Conclusions:
- Spiroplasma citri genotype does not appear to be the primary driver of citrus stubborn disease severity.
- Higher bacterial titers, rather than genotypic differences, are likely responsible for increased symptom severity in infected citrus trees.
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