Abstract
A papaya (Carica papaya L.) variety development program was initiated using breeding lines with transgenic resistance to papaya ringspot virus. Selected PRSV-resistant transgenic lines (R[sub0]) were all female and were crossed with six papaya genotypes to produce the R[sub1] generation. The R[sub1] generation was evaluated in the field in 2001-2002, and the R[sub2] generation, derived from self-pollinated R[sub1] selections, was evaluated in the field in 2002-2003. In the R[sub2] generation, a total of 1263 fruits were harvested from 150 hermaphroditic trees selected from the 1196 trees planted. Mean fruit weight was 1.2 kg for those lines with 'Solo Sunrise' papaya as the original pollen parent and was 2.4 kg for those lines with "Red Lady' as the original pollen parents. The mean weights for the other pollen parents, 'Puerto Rico 6-65,' 'Experimental No. 15,' 'Tainung No. 5' and 'Solo 40' were between these values. Those lines with 'Solo Sunrise' as an original pollen parent also had the highest mean concentration of soluble sugars in fruits. The concentration of soluble sugars declined in January and February when the temperatures were cool. Of the 1196 trees evaluated, 24 trees representing four transgenic lines and the six original pollen parents were selected for production of the next breeding generation.
