Fluctuations in climate and sea level rise have increased the frequency and harshness of drought and other stresses impairing agricultural production. Kale, Brassica oleracea, is a good source of health-beneficial substances. However, locally produced kale only fulfilled 20.9% of the amount consumed in Maryland in 2012. Ensuring adequate and reliable production of kale under drought and high salinity conditions is crucial for increasing net farm income and diversifying produce available to consumers. All fresh produce must also present low risk of foodborne illness such as salmonellosis caused by Salmonella enterica. The association of S. enterica with kale is not well studied and requires further investigation as consumption of raw baby kale increases. Plant growth promoting rhizobacteria (PGPR) colonize plant roots and provide beneficial services to the plant, such as growth promotion and enhanced stress tolerance. PGPR use is a promising way to sustain food production and increase crop resilience under variable conditions. Compounds produced by PGPR alter plant metabolism, and the influence of these changes on associating microorganisms could lead to strategies to enhance crop protection and food safety. In this proposal, I aim to study the beneficial effects of PGPR strains of Pseudomonas putida on growth, nutritional and food safety aspects of kale plants under drought and high salinity stresses. I will disseminate data to growers through local grower meetings. Deliverables from this study will augment current knowledge of PGPR in sustainable agriculture and ways to enhance kale production, nutritional value, safety and resilience.
Project objectives from proposal:
This project aims to evaluate the effects of Pseudomonas putida strains on promotion of kale growth, nutritional value and resilience to drought, salinity and the human pathogen S. enterica under restricted water and high salt conditions. Specifically, this study proposes to investigate how kale plants can mitigate abiotic (drought and salinity) and biotic (S. enterica) stresses in an age-dependent manner in the presence or absence of PGPR strains of P. putida strains S2 and S4 colonizing roots. The objectives of this study are to address three aspects of crop production, growth promotion, nutritional quality and microbial safety.
The specific aims are described below:
1) Promoting Growth: Investigate the effect of root colonization of kale plants with P. putida on plant shoot and root biomass in drought-affected, salt-affected and regularly watered plants. Assessment of biomass accumulation and leaf chlorophyll content using kale plants from different treatments will determine if P. putida associating with kale roots enhance root and shoot biomass accumulation and promoting plant growth under regular watering conditions and protecting kale plants from drought and salt stress without reducing biomass.
2) Improving Nutritional Quality: Investigate the effect of root colonization of kale plants with P. putida on the major health-beneficial bioactive substances of kale plants under regular watering, irrigation-withholding conditions and salt stress. Assessment of kale nutritional value under different treatments will determine if P. putida association with roots induces the synthesis of bioactive compounds under regular watering conditions and protecting kale plants from stress while increasing nutritional value.
3) Ensuring Microbial Safety: Assess the effect of root colonization of kale plants with P. putida on the metabolomic and exo-metabolomic (surface) profiles of leaf tissue and exudates and leaf surface survival of S. enterica Newport under regular watering, irrigation withholding conditions and salt stress. This measurement will reveal if P. putida create a less favorable surface environment for S. Newport under different treatments and change the phytonutrient landscape for bacteria.
4) Providing Educational Opportunities: Promote kale farming and the use of P. putida and other PGPR strains with growers in a sustainable and safe manner. I will provide information on kale production to Maryland growers and point out the need to increase kale farming. I will attend meetings with local growers, present my research and disseminate factsheets summarizing key findings. These seminars aim to promote kale farming and the use of PGPR among growers while considering agricultural and environmental sustainability.