Anther Culture in Jatropha curcas L.: A Tree Species.

The obstacles to breeding programs in Jatropha are the long reproductive cycle with a juvenile phase that lasts several months, the highly heterozygous nature of the genome, the large canopy size, and self-incompatibility that is a long-term process which requires multiple cycles of self-pollination to achieve complete homozygosity. In vitro plant tissue culture-based tools such as haploids and doubled haploid techniques can increase the selection efficiency, resulting into selection of superior plants with complete homozygosity in one generation. It bypasses the complications of greenhouse field evaluation or off-season generation advancement, which takes about 8-10 generations in traditional breeding with the time line of 10-12 years. The haploids have in fact a single set of chromosomes, which undergoes duplication spontaneously during in vitro culture conditions, and are further converted into doubled haploid plants. This represents a major biotechnological tool to accelerate plant breeding. Here, we have established a reproducible, unique anther culture protocol in Jatropha curcas to develop haploid and doubled haploid plants.

De Novo Sequencing and Hybrid Assembly of the Biofuel Crop Jatropha curcas L.: Identification of Quantitative Trait Loci for Geminivirus Resistance.

Jatropha curcas is an important perennial, drought tolerant plant that has been identified as a potential biodiesel crop. We report here the hybrid de novo genome assembly of J. curcas generated using Illumina and PacBio sequencing technologies, and identification of quantitative loci for Jatropha Mosaic Virus (JMV) resistance. In this study, we generated scaffolds of 265.7 Mbp in length, which correspond to 84.8% of the gene space, using Benchmarking Universal Single-Copy Orthologs (BUSCO) analysis. Additionally, 96.4% of predicted protein-coding genes were captured in RNA sequencing data, which reconfirms the accuracy of the assembled genome. The genome was utilized to identify 12,103 dinucleotide simple sequence repeat (SSR) markers, which were exploited in genetic diversity analysis to identify genetically distinct lines. A total of 207 polymorphic SSR markers were employed to construct a genetic linkage map for JMV resistance, using an interspecific F2 mapping population involving susceptible J. curcas and resistant Jatropha integerrima as parents. Quantitative trait locus (QTL) analysis led to the identification of three minor QTLs for JMV resistance, and the same has been validated in an alternate F2 mapping population. These validated QTLs were utilized in marker-assisted breeding for JMV resistance. Comparative genomics of oil-producing genes across selected oil producing species revealed 27 conserved genes and 2986 orthologous protein clusters in Jatropha. This reference genome assembly gives an insight into the understanding of the complex genetic structure of Jatropha, and serves as source for the development of agronomically improved virus-resistant and oil-producing lines.