Germplasm Evaluation, Environmental Impact Assessment and Genetic Improvement Studies in Jatropha curcas

Abstract

The utilization of plant biofuel based Jatropha curcas feedstock is emerging as promising solution to problems of depletion of fossil fuel, fuel crisis and concern over global climate change. Large scale profitable cultivation of Jatropha is still in its infancy due to low and inconsistent yield and slow progress in identification of elite germplasm. Identification of elite germplasm from diverse agro-climatic region vis-a-vis development of superior genotype for higher seed yield and oil content, earlier maturity, reduced plant height, resistance to pests and diseases, drought resistance/tolerance, higher ratio of female to male flowers and improved fuel properties is expected to enhance the utility of Jatropha seed feedstock for biofuel. Adaptation of Jatropha to a wide range of climatic conditions including Northeast India, one of the biodiversity hot spot of the world, suggests existence of considerable genetic variation in growth and seed oil traits which can be potentially harnessed for selection of elite germplasm having high oil content and yield. Systematic analysis of the seed oil content and physicochemical properties forms the basis for identification of elite lines of J. curcas for commercial biodiesel production program. Life cycle assessment of Jatropha based biodiesel production can indicate its environmental impact and this analysis can also assist in adapting to appropriate biodiesel feedstock with minimum impact on environment. Lack of disease and stress tolerant accessions of Jatropha prohibits its successful commercial plantation program. Introduction and expresssion of crystalline toxin genes (cry) derived from Bacillus thuringiensis (Bt) through transgenic approaches have proven as effective mechanisms for protecting crops against insect infestations. In Jatropha, absence of an efficient and reproducible in vitro regeneration system amenable to gene transfer through Agrobacterium-mediated transformation hinders its genetic improvement program. In the present study, elite accessions of J. curcas from Assam, a state in North East India were identified on the basis of their seed trait and oil content. The oil content of the four elite accessions was found in the range of 37.6-46.6%. Analysis of physico-chemical properties of the oil and biodiesel obtained from seeds of these elite accessions demonstrated that they were within acceptable range of standards specifications of ASTM D6751. Life cycle assessment of Jatropha biodiesel production indicated its cultivation process generating highest environmental impact as compared to other stages of its life cycle, and showed higher sustainability of biodiesel from Jatropha as compared to Pongamia. An efficient and reproducible de novo plant regeneration system from cotyledonary leaf segment explants amenable to genetic manipulation through Agrobacterium-mediated transformation was established. The choice of explants of appropriate age and the orientation of the explants in culture medium were found to exert significant influence on the frequency of de novo plant regeneration. Furthermore, the age of the explant was found to be the critical aspect in conferring appropriate biological condition of the explant vital for optimal infection and T-DNA transfer by Agrobacterium tumefaciens. Highest regeneration response was reported.