Opuntia ficus-indica: a climate-resilient biomass feedstock for low-input drylands agriculture
AuthorMayer, Jesse Allen
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Prickly pear cactus (Opuntia ficus-indica) is a rapidly growing member of the Cactaceae that thrives in semi-arid and arid regions with many beneficial traits compared to other species grown under drylands conditions. O. ficus-indica is currently used as a food crop, a forage and fodder for livestock under drought conditions, and as a source for a variety of medicinal and nutraceutical products. While Opuntia ficus-indica is not native to Nevada, the southern region of the state has a large underutilized land area suitable for prickly pear cultivation. O. ficus-indica has been well-characterized from a physiological perspective and is known to possess adaptations including modified photosynthetic stems (cladodes), robust heat and drought tolerance, a thick cuticle, and crassulacean acid metabolism. The molecular composition that drives these adaptations is not well known. Furthermore, the tools needed to further analyze mechanisms, including genetic transformation and genome editing, have not been established in this species. The goal of this work is to develop Opuntia ficus-indica both as a model to understand adaptations that allow biomass productivity on semi-arid lands and as a platform for producing food, forage, fodder, and fuel in areas uninhabitable by traditional crops. Molecular analysis of the Opuntia cuticle has identified putative polymeric aldehydes in the epicuticular wax layer and recalcitrant epoxy-ω-hydroxy fatty acids in cutin that might help to reduce water losses through the cuticle. A metabolic study using well-watered and water-deficit stressed mesophyll and epidermis tissues identified numerous responses to an oxidative environment including high tryptophan, raffinose family oligosaccharides, and oxidized glutathione levels. Analysis of the forage quality of O. ficus-indica combined with a three-year field trial in southern Nevada demonstrated high productivity with minimal irrigation and an adequate nutrient and mineral content for livestock consumption. While attempts to genetically transform O. ficus-indica stably were unsuccessful, a transient transformation protocol was developed successfully to test the ability to produce oils in vegetative tissues of O. ficus-indica.