The interspecific hybrid Petunia parodii � P. inflata and its relevance to somatic hybridization in the genus Petunia

Abstract

Attempts at the reciprocal cross between Petunia parodii and P. inflata using standard emasculation and pollination techniques failed. Limited pollen tube growth down the style in reciprocal crosses led to reproductive isolation between the self-compatible P. parodii and self-incompatible P. inflata. The interspecific hybrid was successfully produced by bud-pollination of P. parodii with P. inflata as the male parent in 22 percent of attempts, but not in the opposite direction. In vitro pollination of P. parodii ovaries with P. inflata pollen also produced hybrids. The small size of the ovary made it technically impossible to use P. inflata as the female parent for in vitro pollination. The interspecific hybrids were intermediate, as compared to the two parents, for six of the seven plant and flower characters measured. Furthermore, the hybrids had high pollen fertility, set abundant seed upon self-pollination, and readily inter-crossed with the parental species. The results are consistent with a high degree of chromosomal homology in the parental species and with minor genetic divergency leading to reproductive isolation that is pre-zygotic in nature. Overcoming the barriers to cross-incompatibility by practical techniques resulted in fertile interspecific hybrids that segregated for parental characters. The potential value of employing the parental species in somatic hybridization experiments is discussed.

Pollen Tube Growth in Interspecific Crosses between Capsicum Species

“…Apparently, pollen tubes may overcome the barriers in the ovaries that we observed. Several experimental approaches, such as bud pollination or in vitro pollination, have been applied in other crops (Namai, 1980;Sink et al, 1978). Such approaches might also be successfully applied in Capsicum breeding programs aimed at the introduction of a character from incongruent species.…”

Protoplast Fusion for Plant Improvement

“…Horticultural crops regenerated from protoplasts. Subsequently, somatic hybrids were produced between P. parodii {In -14) and P. inflata Fries (2n = 14), two species which exhibit unilateral incompatibility, with pollination of the former species mandatory at the bud-stage to obtain the hybrid (32,41). Selection of somatic hybrid callus was based on limited growth of P. parodii, albino color of chlorophyll-deficient P. inflata and both sustained division and competency for chlorophyll synthesis in the hybrid cells.…”

Wide Crosses in Herbaceous Perennials1

“…With morphological manipulation. Emas culation to preclude selfing, stylar excission to reduce the physical distance from stigma to ovule so that pollen tubes from remote male parents can successfully traverse the length of the style, and removing or bypassing mechan ical obstacles that may prevent pollen from reaching the stigmatic surface can improve chances for success (43,78,97).…”

“…Excised pistils can be pollinated and maintained in an environment which is " ideal" for the repro ductive processes to occur. By reducing com petition from other plant organs for growth regulators, nutrients, water, etc., it may be possible to complete some difficult crosses (61,78,98).…”