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United States Department of Agriculture

Agricultural Research Service

Research Project: Pacific Fruit Genetic Resource Management and Sustainable Production Systems

Location: Tropical Plant Genetic Resources and Disease Research

Title: Genome size variation among sex types in dioecious and triecious Caricaceae species

Authors
item Gschwend, Andrea -
item Wai, Ching Man -
item Zee, Francis
item Arumuganathan, Aru -
item Ming, Ray -

Submitted to: Euphytica International Journal on Plant Breeding
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 28, 2012
Publication Date: October 20, 2012
Repository URL: http://handle.nal.usda.gov/10113/56411
Citation: Gschwend, A.R., Wai, C., Zee, F.T., Arumuganathan, A.K., Ming, R. 2012. Genome size variation among sex types in dioecious and triecious Caricaceae species. Euphytica International Journal on Plant Breeding. DOI: 10.1007/s10681-012-0815-9.

Interpretive Summary: The family Caricaceae consists of 35 species most of which resides in subtropical and tropical regions of North and South America. The genus Carica contains one species, papaya, which is agronomically important worldwide. Vasconcellea or “highland papaya” is the largest genus with 21 species. Caricaceae species are sexually dimorphic, 32 of the 35 species are dioecious having separate male and female individual. Papaya and Vasconcellea cundinamarcensis are trioecious (male, female and Hermaphrodite individuals, and V. monoica has separate male and female flower on the same plant (monoecious). Sex plays a large role in the agriculture of papaya, since the sex of papaya trees cannot be physically determined until the plant flower. This study determined whether genome size difference can be detected between the sexes in 11 species from three of the six genera (Carica, Jacaratia and Vasconcellea) using flow cytometry. Genome sizes ranged from 442.5 to 625.9 megabases (Mb) likely due to variation in the accumulation of retrotransposons in the genomes. The C. papaya genome size was estimated to be 442.5 Mb, larger than previously reported. Significant differences were detected between male and female samples in Jacaratia spinosa, Vasconcellea horovitziana, and V. stipulata, and between male and hermaphrodite. The small size differences between genomes of the papaya sexes were not detected using flow cytometry. The project also provides insight into whether these Caricaceae species have sex chromosomes. The genome size can be used as references for future Caricaceae genome sequencing project genome size of a variety of species.

Technical Abstract: Caricaceae is a small family consisting of 35 species of varying sexual systems and includes economically important fruit crop, Carica papaya, and other species of “highland papayas”. Flow cytometry was used to obtain genome sizes for 11 species in three genera of Caricaceae to determine if genome size differences can be detected between sexes. Genome sizes ranged from 442.5 to 625.9 megabases (Mb) likely due to variation in the accumulation of retrotransposons in the genomes. The C. papaya genome size was estimated to be 442.5 Mb, larger than previously reported. Significant differences were detected between male and female samples in Jacaratia spinosa, Vasconcellea horovitziana, and V. stipulata, and between male and hermaphrodite samples of V. cundinamarcensis, suggesting the presence of sex chromosomes for these species. The small size differences between genomes of the papaya sexes were not detected using flow cytometry. Vasconcellea horovitziana was discovered to have a larger female genome size than male, suggesting the possibility of a ZW sex chromosome system in the family. The estimated genome sizes of these 11 species will be used in sequencing their genomes and in sex chromosome research for this family.

Last Modified: 10/1/2014
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