**15. Targeting enhanced oil production in** *Jatropha curcus*

Various plant breeding strategies are employed in the last few decades to increase oil yield and quality, as well as resistance to biotic and abiotic challenges in edible and non-edible oil plants. Marker-aided selection, next-generation sequencing, "omics" technologies, and genetic engineering are some of the new biotechnological methods that have sped up the breeding process for such features in these plants. The use of omics technologies to identify and isolate important genes involved in lipid biosynthesis pathways, as well as their transfer to edible and non-edible oil plants is predicted to result in cost-effective oil production as a feedstock for biodiesel generation [112]. Biodiesel production from non-edible oil plants would be far more realistic if new varieties/hybrids of oil plants could be developed that contain more oil, are resistant to biotic and abiotic challenges, and do not contain harmful proteins. Through various breeding techniques, oil plants that produce edible and non-edible oils have increased these properties over recent decades. In the field of plant breeding, development, selection, target trait evaluation, multiplication, and distribution are the major objectives [113, 114]. Breeding targets for various crops have been rapidly accelerated by genetic and metabolic engineering techniques over the last few decades. Genetic engineering can be used to increase the amount of oil found in seeds of nonedible plants by engineering lipid biosynthesis pathways [115]. It is the simplest and most efficient way to increase oil yields in nonedible plants. Furthermore, the expression of genes encoding fatty acyl carrier thioesterase A (FatA), glycerol-3-phosphate dehydrogenase (GPD), and lysophosphatidyl-acyltransferases (LPAT) has enhanced the oil production pathway and therefore could be regarded as key genes to boost oil content in bioenergy plants [113, 116]. Engineering other genes involved in agronomical traits such as seed, fruit, and leaf size, plant growth and biomass, root architecture, and vegetative/reproductive transition, in addition to the genes involved in TAG biosynthesis.


#### **Table 2.**

*Genetic manipulation strategies used to improve Jatropha.*

Genetic engineering for oil content has a significant impact on the potential of bioenergy plants as a source of biodiesel production. Because seed size plays such an essential role in Jatropha oil yield, it has been prioritized as a breeding target to improve oil yields. In Jatropha, a candidate gene (CYP78A98) with the potential to increase seed size has just been discovered [117, 118]. Improvement of Jatropha through genetic engineering was listed in **Table 2**. The growing demand for biofuels has prompted plant scientists to develop plant feedstocks specifically for biodiesel production, using either traditional or modern breeding techniques to develop oilseed varieties with higher oil content and optimal fatty acid composition. Biodiesel is a fuel made up of mono-alkyl esters of long-chain fatty acids derived from plant oils, with the majority of the fatty acids being triacylglycerols (TAGs) and shortchain alcohols (>95%). Waste vegetable oils and non-edible crude vegetable oils are another source of biodiesel that reduces its price. Jatropha, castor bean, cotton, Pongamia, tobacco, mahua, neem, and Camelina are currently used as non-edible oil yielding plants for second-generation biodiesel production [131]. Gene editing techniques like CRISPR can be used in precision breeding to improve yield, disease resistance, herbicide resistance, induce haploids, fix hybrid vigor, solve self-incompatibility, and help de novo domesticate oil crops. While it will likely be a long time before genome-edited oil crops become commercially available, we anticipate that regulatory constraints on them will gradually be eased in the near future [132].
