Cytological characterization of an interspecific hybrid in Jatropha and its progeny reveals preferential uniparental chromosome transmission and interspecific translocation

Genetic variation in Jatropha curcas, a prospective biodiesel plant, is limited, and interspecific hybridization needed for its genetic improvement. Progeny from interspecific crosses between J. curcas and Jatropha integerrima can be used to improve agronomic characters and to increase oil content and yield. However, these hybrids have not been characterized cytologically. The present study was aimed at the analysis of chromosome behavior during meiosis and chromosome composition of S(1) plants derived from an interspecific F(1) hybrid using genomic in situ hybridization (GISH) and fluorescence in situ hybridization (FISH). Bivalents that formed as a result of interspecific pairing were frequently observed, suggesting the presence of homoeologous chromosomes from the two species. Almost half of microspores were derived from the reduction division; GISH analysis indicated random transmission of the parent chromosomes to microspores. Male fertility measured as pollen staining with acetocarmine was 48.4%. In contrast, GISH analysis of S(1) plants revealed preferential transmission of J. curcas chromosomes. We also found segment exchange between chromosomes of the two species (interspecific translocation) by GISH and FISH analyses. Introgression of J. integerrima chromosome segments into the J. curcas genome would help to improve Jatropha cultivars for mass production.