Crossability In Interspecific Hybrid Between Eucalyptus Pellita and E. Urophylla

A controlled crossing experiment using a factorial mating design, involving female parents of E. pellita and male parents of E. urophyla that randomly sampled from the breeding population of both species, was conducted to assess the degree of genetic control on interspecific crossability for hybrid between E. pellita and E. urophylla. As measures of crossability, number of seeds per capsule and percentage of germinated seed were determined for each individual cross. The effect of female, male and female × male was significant on number of seed per capsule and percentage of germination. There was a slight tendency that the family produced more viable seed might produce less viable seed. Additive and dominance genetic varians were estimated as measures of the genetic control. The dominance variance had the major contribution to the genetic control of seed production and seed germination. Female source of variation has the major contribution to the additive genetic influence. Therefore, to maximize the production of viable seed, parent trees with desired traits should be selected on specific cross basis.

Interspecific Crossability of Nine Diploid Fragaria Species

As part of a wild species introgression program, Fragaria vesca, F. viridis, F. nubicola, F. nipponica, F. nilgerrensis, F. pentaphylla, F. gracilis, F. daltoniana, and F. iinumae were crossed in most combinations possible, the exceptions being F. daltoniana and F. iinumae, which produced only a few flowers each. Crosses with F. vesca as a female and either F. gracilis, F. nipponica, or F. iinumae as males produced good seed set, but seedlings died in the cotyledon stage in every case. No seed set occurred when F. iinumae was crossed with F. viridis or F. nubicola. F. pentaphylla, F. gracilis, and F. iinumae were observed to be self-incompatible while F. daltoniana was self-compatible. Three overlapping groups based on crossing data have emerged. Within the following groups, hybrid plants were obtained in all species combinations, although not necessarily for reciprocal combinations: Group A: F. vesca, F. viridis, F. nubicola, and F. pentaphylla. Group B: F. vesca, F. nilgerrensis, F. daltoniana, and F. pentaphylla. Group C: F. pentaphylla, F. gracilis, and F. nipponica. Fertile or semifertile diploid hybrids were obtained for all species combinations within group A indicating genomic similarity or that breeding at the diploid level could occur with these species. Fertility has not been determined for hybrids in groups B and C. It is interesting to note the presence of F. pentaphylla in all three groups, perhaps this species plays an important role in Fragaria evolution.

Interspecific Crossability of Fragaria vesca as a Female Parent

Fragaria vesca has been introgressed into F. ×ananassa in the form of decaploids and synthetic octoploids. As F. vesca is self-incompatible and crosses with most diploid Fragaria species when used as a female parent, it could serve as a bridge for introgression of additional genetic material. A primary goal of this study was to screen selections of F. vesca for interspecific crossability among diploid species. The F. vesca collection included 10 cultivars of the alpine strawberry, F. vesca var. semperflorens, as well as 30 wild runnering types gathered from around the world. The following diploid species were represented by one to three genotypes each: F. viridis, F. nubicola, F. nipponica, F. nilgerens, F. iinumae, F. daltoniana, F. gracilis, as well as two unnamed species from China. Fragaria vesca was used as the female parent and the other species provided the pollen. Crossing took place in the greenhouse, with one pollination occurring during the “popcorn” or “balloon” stage. Germination was performed in vitro using cut achenes shortly after fruit ripening. The alpine strawberry cultivars were easier to cross than wild selections of F. vesca. Their continuous blooming habit combined with higher positioning of flowers allowed for easier and perhaps less-damaging emasculation. Crossability, as measured by seed set and germination, was more variable in wild-type F. vesca and generally lower than alpine strawberry cultivars.