Page:Report of the Puerto Rico Experiment Station (IA CAT31294391015).pdf/13

 higher percentages of fruits and seeds obtained this year. Crosses this year included two new Jersey varieties (Yellow Jersey and Maryland Golden) and the new Fusarium-resistant, moist-flesh types (Introductions 153655, 153907, and 153909)

Of the 337 hybrid seeds produced this year, 116 are from crosses between Jersey and moist-flesh varieties 12 with a Jersey variety as the female parent and 104 with a Jersey variety as the male parent. Although a scarcity of flowers limited the number of crosses that could be made with Maryland Golden and Yellow Jersey these varieties appear to be more fertile than Orange Little Stem. The Jersey varieties, as a whole, set 11.21 seeds per 100 crosses when used as the female parent and 7.26 seeds per 100 crosses when used as the male parent. Among the moist-flesh varieties, Introductions 153907 and 153909 proved to be exceptionally fertile as females, with seed-sets of 30.38 percent and 21.97 percent, respectively. The native varieties, Mameya and Toro Negro Wild, were highly fertile as male parents, with seed-set percentages of 36.58 and 42.86, respectively. No seeds were obtained from a limited number of crosses with the varieties L-138, Queen Mary, and UPR-3.

The moist-flesh varieties, as a group, set 15.46 seeds per 100 crosses when used as a female and 29.99 seeds per 100 crosses when used as a male. Setting was poor at the beginning and at the end of the season (October-November, and the last part of March) and high during the middle of the season (January 16 to February 15). During the first 15 days of February, an average of 41.20 seeds were obtained for each 100 crosses. Numerous tests on emasculation and crossing techniques were carried out during the early part of the season. These tests indicate considerable cross-fertility, a high degree of self-sterility, a detrimental effect of bags for protection against insects, and that emasculation and protection techniques used were safe, and the emasculated flower (with petals removed) has little attraction for insects.

H. E. Warmke and H. Cruzado

Forty-four different varieties and introductions of papaya, Carica papaya L., coming from widely separated locations in the West Indies, South and Central America, Florida, Africa, and the Hawaiian Islands have proved susceptible to the destructive virus disease, "bunchy-top," in experimental plantings in Puerto Rico. At the end of 21 months no single line had escaped infection with the disease, and most of the plants were killed in plots at Mayagüez and Isabela. The few remaining healthy plants are to be experimentally infected with the virus to determine whether they are genetically resistant individuals, or only chance escapes from infection. Many valuable genes for fruit size, shape and quality, growth habits, and setting characteristics have been discovered in these stocks. Plants of the related species, Carica gaudotiana, C. monoica, Jacaratia hassleriana, and J. dodecaphylla have not exhibited symptoms of the disease in field plots, and some of these may possess true resistance.

E. P. Hume and N. Almeyda An experiment was conducted to determine the effect of various pruning methods and root treatments on the survival and subsequent growth of transplanted mangos, Mangifera indica L. The plants were dug, subjected to the treatments, and carried by truck and