Karyotype and genome size determination of Jarilla chocola, an additional sister clade of Carica papaya

Jarilla chocola is an herbaceous plant species that belongs to the Jarilla genus and the Caricaceae family. No information on chromosome number or genome size has been reported for J. chocola that confirms the occurrence of dysploidy events and explore the existence of heteromorphic sex chromosomes. Therefore, the total number of chromosomes of this species was determined by karyotyping and counting the number of chromosomes observed, and the genome size of female and male plants was estimated separately by flow cytometry. Results showed that J. chocola has eight pairs of chromosomes (2n = 2x = 16), and its chromosomes are classified as metacentric for five pairs, submetacentric for two pairs and telocentric for one pair. The nuclear DNA content (1C-value) in picograms and diploid genome size was estimated separately from female and male plants using two species as the standards, Phaseolus vulgaris (1C = 0.60 pg) and Carica papaya (1C = 0.325 pg), to look for the possible existence of heteromorphic sex chromosomes. C. papaya proved to be a better standard for the determination of J. chocola DNA content and diploid genome size. No significant difference on the DNA content was observed between female (1C = 1.02 ± 0.003 pg) and male (1C = 1.02 ± 0.008 pg) plants. The estimated genome size of J. chocola per haploid genome in base pairs was calculated from the obtained C-values. Results showed an estimated genome size per haploid genome of 1018.44 ± 3.07 Mb and 1022.08 ± 7.76 Mb for female and male plants, respectively. Due to the observed chromosome number and genome size, only the occurrence of one of two previously reported dysploidy events in Jarilla could be confirmed for J. chocola and no evidence of heteromorphic sex chromosomes was found. These results provide fundamental information of the J.