- Vegetables: tomatoes
- Additional Plants: ginger, other
- Crop Production: other
- Education and Training: extension
- Pest Management: competition, cultural control, disease vectors, eradication, integrated pest management, mulching - plastic, other, prevention, soil solarization
- Production Systems: agroecosystems, organic agriculture
- Soil Management: organic matter, other, soil chemistry, soil microbiology
- Sustainable Communities: other, quality of life
This applied crop disease research project is designed to evaluate a novel solution for farmers struggling with bacterial wilt diseases caused by Ralsonia solanacearum. This pathogen damages a remarkably broad range of crops. In the Western SARE region, R. solanacearum is particularly harmful to Zingiberaceae crops in Hawaii such as ginger (Zingiber officinale) and turmeric (Curcuma longa). Outbreaks in ginger spread quickly. They often lead to total losses in fields exposed to the pathogen (Yu 2003), which can remain indefinitely in the soil without effective means of remediation. Because of this, farmers are forced to frequently move their operations, sometimes even carrying the disease along with them on unsanitary equipment or in latently infected seed rhizome (Nelson 2013).
This research will test an organic management approach called anaerobic soil disinfestation (ASD) for suppressing diverse strains of R. solanacearum, including isolates pathogenic to ginger. Recent studies have shown ASD effectively suppresses strains infectious to other crops. A hopeful example is potato brown rot, caused by a distinct phylogeny of R.solanacearum, exhibiting remarkable suppression through ASD (Messiha 2007). This project will simulate ASD field treatments in soil mesocosms inoculated with diverse global strains for post treatment analysis of pathogen survival and virulence to susceptible host plants. The approach will determine whether ASD could be an effective management strategy for farmers in the Western region.
Research findings will be disseminated to growers through a combination of public presentations to farmer organizations, print and online publications, and through partnership with Hawaii Cooperative Extension.
Project objectives from proposal:
This project will determine whether ASD is an effective management approach against diverse R. solanacearum phylogeny, and it will also examine the taxonomy of R. solanacearum strains that infect Hawaiian turmeric.
Objective 1: Compare virulence of R. solanacearum wild-type ginger isolates with diverse global strains on model host plants
Use a controlled experimental approach to test the hypothesis that wild-type ginger isolates are also pathogenic on tomatoes, a practical model host and bioindicator plant, and establish baseline virulence data through observation of wilt symptoms after soil soak inoculations.
Objective 2: Examine R. solanacearum soil population density and virulence responses to ASD treatment amongst diverse natural isolates, including a virulent wild-type ginger strain.
Use controlled experimental approaches to test the hypotheses that ASD treatment will cause reductions in R. solanacearum soil bacterial concentrations and will also reduce wilt symptoms observed in tomatoes transplanted into post treatment soil as compared to controls.
Objective 3: Identify the taxonomic position of R. solanacearum from infected turmeric (Curcuma longa) plants in Hawaii.
Use DNA-based taxonomy to characterize the phylogeny of R. solanacearum isolates collected from infested Hawaiian turmeric crops and soil sampled from infested croplands in relation to known ginger strains.