Study of morpho-agronomic diversity and oil content in desert gourd (Citrullus colocynthis (L.) Schrad.)
Citrullus colocynthis (L.) Schrad., also known as desert gourd, is a xerophytic perennial creeper. In a field trial conducted on sandy soil and under arid conditions in the United Emirates (UAE), 27 germplasm accessions were studied for their potential as feedstock for biodiesel production. All accessions were evaluated for two qualitative and eleven quantitative morpho-agronomic traits over a period of one year (November 2013- December 2014) in a field trial laid out in a randomized complete block design with three replicates. Analysis of the data revealed high variability among the accessions, with seed yields ranging between 12 and 374 grams per plant and seed oil content from 7.8 to 43.8% of seed weight. When the data were statistically analyzed using principal components analysis, traits of economic importance such as seed yield, oil content and number of fruits per plant grouped together, while others such as number of branches and branch length grouped separately. Agglomerative hierarchical clustering grouped the accessions into three main clusters. The extrapolated annual oil yield in several accessions exceeded 1 ton ha-1 (the highest being 3.44 tons ha-1) – showing the desert gourd to be a highly attractive biodiesel feedstock species for cultivation on marginal lands. The oil from most accessions had a free fatty acid content of less than 0.5% which is within suitable limits for biodiesel production. The observed variability in saponification values suggests that the oil is prone to oxidation upon storage. The wide range of variation found in this study for seed yield, oil quantity and oil quality provides the opportunity for genetic improvement to develop desert gourd into an economically-viable, non-edible, alternative biodiesel feedstock crop.