Peering into papaya's sex life

Agricultural Research, Sept, 2004 by Paul H. Moore

Both people and papayas have specialized chromosomes that carry genes that determine the gender of their offspring. They're called the sex chromosomes and are markedly different from ordinary chromosomes. Joint research with industry and university scientists has yielded the first direct evidence of the evolution of papaya sex chromosomes from others in the fruit's genetic makeup. One particular papaya chromosome resembles a primitive version of the human Y chromosome--perhaps as it existed 240 to 320 million years ago. It's thought that a similar process occurred in the human genome over millions of years of human sex chromosome evolution.

While sex-chromosome studies may explain inheritance of human conditions such as sickle-cell anemia or hemophilia, similar studies of papaya may shed light on inheritance traits responsible for the fruit's size, shape, and quality. In choosing papaya, consumers seem to prefer an elongated shape that's been linked to a specific combination of genes. Researchers want to find a way to make sure that more commercial papayas inherit this prized attribute. Paul H. Moore, USDA-ARS U.S. Pacific Basin Agricultural Research Center, Aiea, Hawaii; phone (808) 486-5411, e-mail pmoore@ pbarc.ars.usda.gov.