- Seed and transplant physiology: Impact in onion establishment
- Soil amendments and health: Applications on plants and soil-biota growth
- Tomato grafting: High tunnel and field production systems
- Organic systems: Soil health and phytochemicals in globe artichoke
- Hydroponics: Water and nitrogen management for leafy vegetable
- Genetic × Environment × Management (G×E×M) for stress tolerance, yield, and quality
Maximizing crop yield, quality and resource use efficiency in water limited areas and less fertile soils are major challenges under the increasing population, intense farming practices and climate change of south Texas. The Vegetable Physiology research program aims at understanding plant adaptation mechanisms to abiotic stresses (water limitation, drought and heat stress) and in developing sustainable cropping systems for high-value crops.
Seed and transplant physiology: Impact in onion establishment
Plant growth regulators (PGRs) can positively regulate seed germination and/or root growth and development. Research in onion seeds showed the PGR ethephon, to be beneficial in increasing seedling root surface area but reduced root length. Hydro-priming was shown to be a simple and viable method to enhance onion germination and root traits. A follow-up study aimed at selecting the best transplant strategies to improve onion crop performance. The impact of later planting dates and seedling densities in the trays were evaluated on growth, yield components, bulb quality and phytonutrient content of three onion cultivars (‘Caramelo’, yellow; ‘Don Victor’, yellow; and ‘Lambada,’ red). Our results demonstrated that the technique of establishing onion transplants grown from 1 or 3 seeds per cell in a tray from early November to early December provides a practical and economical alternative to achieve earlier crops while reducing the length of the production season.
Soil amendments and health: Applications on plants and soil-biota growth
Organic matter-derived soil amendments containing humic substances (HS) have a functional role in improving plant growth and soil quality. A recent study assessed the impact of lignite-derived HS on biota growth and evaluated their potential mitigative effects under water deficit stress in bell pepper plants grown in sandy and clay soil previously mixed with HS. Our results showed that HS increased plant root development and soil bacteria population in moderate and no stress conditions (60%, 80% water holding capacity). Physiologically, HS rapidly decreased leaf stomatal conductance and transpiration (reducing water loss) after imposing severe or mild stress (20%, 40%). Due to their capacity to improve plant root growth, soil nutrient cycling, and microbial activity, application of HS may have long-term benefits in agricultural systems. A follow-up HS study using path analysis distinguished abiotic factors that affected the rhizosphere microbial biomass in a bell pepper system. This study can be a reference to establish applied approaches to improve the persistence and benefits from rhizosphere microbial communities.
Tomato grafting: High tunnel and field production systems
Successful integration of tomato grafting with high tunnels (HT) could open new opportunities for the Texas tomato industry by using vigorous rootstocks for effectively managing soil diseases, abiotic stresses, and improve fruit quality and yield. Multilocation trials were conducted to evaluate the yield performance of grafted tomatoes in HT and open-field (OF) environments. Overall the HT system enhanced marketable yields by 116-161% relative to OF systems, with an additional 8-23% increase due to grafting adapted cultivars with interspecific rootstocks. Results from these studies demonstrated that grafting along with a protected environment system clearly has the potential to significantly increase tomato profitability. Current studies are focused on:
- Nutritional fruit quality such as sugars and antioxidant metabolites
- Root traits in commercial and TAMU rootstocks under water and nitrogen deficit
- Biochemical basis of drought tolerance in wild tomato accessions (Solanum pennellii, S. peruvianum S. habrochaites)
- Quality of grafted transplants based on enhanced root growth.
Organic Systems: Soil Health and Phytochemicals in Globe Artichoke
Soil amendments using organic fertilizers are widely used to dispose of animal waste, reduce environmental pollution and improve soil and fruit quality. A new study assessed the influence of plant- and animal-based soil amendments on soil nutrient availability, CO2 respiration (soil health indicator), yield and phytochemicals of artichoke (Cynara cardunculus cv. 179) heads. After two years of organic soil amended with plant-based fertilizer (alfalfa meal), soil respiration and content of organic matter (OM) was higher than when using animal-based fertilizers (fish meal, blood meal, and chicken manure). Conversely, marketable yield from soil amended with chicken manure and a fish meal was higher but with heads having less concentration of phytochemicals than those modified with alfalfa meal. Plant-based fertilizer can be an ideal option to improve soil and head quality of artichokes, but animal-based sources might be an appropriate choice for organic farmers when yield and cost are the main concerns. A second study also assessed the influence of organic and conventional production systems on growth, yield, quality and soil chemical properties of 7 artichoke cultivars. Overall the open pollinated cv. Imperial Star had the lowest yield and head quality. Plants grown in a conventional field have higher growth, physiological responses, and returns in comparison with an organic field; however, the latter produced higher quality artichoke heads with an increase in chlorogenic acid by 31% and cynarin by 12%. Notably, soil respiration-CO2 in the organic field increased by 20-fold compared to the conventional field. Our study suggests that organic farming was the best system to improve soil and artichoke head quality, but it may not be the best option for farmers when yield is the primary target short-term.
Hydroponics: Water and Nitrogen Management for Leafy Vegetables
Understanding growth, water use, N-nutrient uptake, and utilization is a prerequisite to effectively managing irrigation and fertilization programs in any cropping system including leafy vegetables in hydroponic systems. Earlier studies demonstrated the significant water savings (up to 90%) of lettuce cultivars grown in hydroponics versus open field cultivation under drip or center pivot systems. In a recent follow-up N-nutrition study we concluded that a pre- and post-transplant nutrient solution of up to 150 mg L−1 N was sufficient to ensure optimal growth and maximum yield of lettuce cultivars. Following the management strategies selected for Romaine and Bibb lettuce types, on-going studies are targeted to screen and select leafy Asian vegetables.
Genetic × Environment × Management (G×E×M) for Stress Tolerance, Yield and Quality
In conjunction with breeders, projects are focused on high-value vegetables such as fresh-market tomato and specialty melons rich in nutrients, vitamins and antioxidants, compounds important for human health. We are integrating production strategies with new soil, and canopy sensing methods to screen and select superior germplasm with potential for abiotic/biotic stress tolerance, high nutrition and adapted to hot and water-limited environments. The goal is to design specific cultural practices for new ‘branded products’ for growers, with the hope to create new opportunities to increase market share in Texas. Genotypic traits of interest are high root vigor, improved canopy growth, high fruit set, earliness, pest and disease resistance, water use efficiency, high flavonoids, carotenoids, vitamin C and sugars.
Dr. Daniel Leskovar
- Desire Dijdonou, Ph.D. Research Associate
- Madhumita Joshi, Ph.D. Research Associate
- Carrie Hensarling, Research Associate
- Manuel Pagan, Technician II
- Kuan Qin, Ph.D. student
- Samikshya Bhattarai, MS Student
- Michael Contreras, Undergraduate
- Juan Hernandez, Program Aide
Recent Related Publications (2017-2018)
- Macias-Leon, M. A. and D.I. Leskovar. 2018. Containerized onion transplant: Management systems to enhance growth, yield and quality. HortScience (In revision).
- Othman, Y.A. and D. I. Leskovar. 2018. Nitrogen management influenced root length intensity of young olive trees. Scientia Horticulturae (accepted).
- Leskovar, D.I. and Othman. 2018. Nitrogen management for improving root and shoot components of young ‘Arbequina’ olives. 2018. HortScience (accepted).
- Sharma, S.P., D.I. Leskovar and K.M. Crosby. 2018. Genotypic differences in leaf gas exchange and growth responses to deficit irrigation in reticulatus and inodorus melons (Cucumis melo L.). Photosynthetica (in press)
- Leskovar, D.I. and Y. Othman. 2018. Organic and conventional farming differentially influenced soil respiration, physiology, growth, and head quality of artichoke cultivars. Journal of Soil Science and Plant Nutrition http://dx.doi.org/10.4067/S0718-95162018005002502
- Sharma, S.P. and D.I. Leskovar. 2018. Phenotyping root traits for vegetable crop improvement: Advanced tools and techniques. Agric Res J 55 (3): 411-420, 2018 DOI No. 10.5958/2395-146X.2018.00076.5
- Sharma, S.P., Leskovar, D.I., Volder, A., Crosby, K.M., and A.M.H. Ibrahim. 2018. Root distribution patterns of reticulatus and inodorus melon (Cucumis melo L.) under subsurface deficit irrigation. Irrigation Science https://doi.org/10.1007/s00271-018-0587-7
- Mancini, M., Lanza Volpe., M., Gatti, B., Malik, Y., Moreno, A.C. Leskovar, D.I. and V. Cravero. 2018.Characterization of cardoon accessions as feedstock for biodiesel production. Fuel 235:1287-1293.
- Qin, K. and D.I. Leskovar. 2018. Lignite-derived humic substances modulate pepper and soil-biota growth under water deficit stress. Journal Plant Nutrition and Soil Science (1-9) DOI: 10.1002/jpln.201800078
- Othman, Y. and D.I. Leskovar. 2018. Organic soil amendments influence soil health, yield, and phytochemicals of globe artichoke heads. Biological Agriculture & Horticulture. DOI: 10.1080/01448765.2018.1463292
- Kyriacou, M.C., Leskovar, D.I., Colla, G., and Y. Rouphael. 2018. Watermelon and melon fruit quality: The genotypic and agro-environmental factors implicated. Scientia Horticulturae 234:393-408. https://doi.org/10.1016/j.scienta.2018.01.032
- Dong, X. Peng, B., Liu, X., Xue, Q, and D.I. Leskovar.2018. A rapid method for estimating plant root distribution pattern from field measurements. Computers and Electronics in Agriculture
- Agehara, S., Crosby, K., Holcroft, D. and D.I. Leskovar. 2018. Optimizing 1-methylcyclopropene concentration and immersion time to extend shelf life of muskmelon (Cucumis melo L. var. reticulatus) fruit. Scientia Horticulturae 230:117-125. https://doi.org/10.1016/j.scienta.2017.09.021
- Leskovar, D.I. and Othman, Y. 2018. Efficacy of 1-methylcyclopropene in promoting shoot growth of tomato transplants. Acta Hortic. 1204, 229-234 DOI: 10.17660/ActaHortic.2018.1204.30https://doi.org/10.17660/ActaHortic.2018.1204.30
- Macias-Leon, MA. and D.I. Leskovar. 2017. Plant growth regulator effects on germination and root traits of ‘Lambada’ and ‘Don Victor’ onion cultivars. HortScience 52(12):1759–1764. 2017. doi: 10.21273/HORTSCI12473-17
- Goreta Ban, S., Selak, G.V., and D.I. Leskovar. 2017. Short- and long-term responses of pepper seedlings to ABA exposure. Scientia Horticulturae 225, 243-251.https://doi.org/10.1016/j.scienta.2017.06.047
- Liu, X., Feakins, S.J., Dong,X., Xue, Q., Marek, T., Leskovar, D.I., Neely, C.B. and M.H Ibrahim. 2017. Experimental study of leaf wax n-alkane response in winter wheat cultivars to drought conditions. Organic Geochemisty 113:210-223. https://doi.org/10.1016/j.orggeochem.2017.07.020
- Agehara, S. and D.I. Leskovar. 2017. Growth suppression by exogenous abscisic acid and uniconazole for prolonged marketability of tomato transplants in commercial conditions. HortScience 52(4):605-611. doi: 10.21273/HORTSCI11518-16
- Shinohara, T. Martin, E.A., and D.I. Leskovar. 2017. Ethylene regulators influence germination and root growth of globe artichoke seedlings exposed to heat stress conditions. Seed Science and Technology, 45, 1-12.
- Sharma, S.P., Leskovar, D.I., Crosby, K. and A. Volder. 2017. Root growth dynamics and fruit yield of melon (Cucumis melo L) genotypes at two locations with sandy loam and clay soils. Soil & Tillage Research 168:50-62.https://doi.org/10.1016/j.still.2016.12.006
- Liu, X., Dong, X., Xue. Q., Leskovar, D.I., Jifon, J., Butnor, J.R. and T. Marek. 2017. Ground penetrating radar (GPR) detects fine roots of agricultural crops in the field. Plant Soil. https://doi.org/10.1007/s11104-017-3531-3