Pollen tube growth in interspecific crosses between Capsicum species

Crossing barriers between white- and purple-flowered species were exam- ined. Four accessions of Capsicum annuum and three of C. pubescens were reciprocally crossed with one to four accessions of C. baccatum, C. cardenasii, C. chacoense, C. chinense, C. eximium, C. frutescens, C. galapagoense, and C. praetermissum . Capsicum chacoense is the only white-flowered species that inhibits C. annuum pollen tube growth but allows C. pubescens pollen tube penetration into the egg cell. Capsicum cardenasii and C. eximium exhibit similar crossabilities with C. annuum and C. pubescens: pollen tubes of C. cardenasii and of C. eximium can penetrate the egg cells of C. annuum but not vice versa, and pollen tubes of C. pubescens can penetrate the egg cells of C. cardenasii and of C. eximium but not vice versa. The crossabilities between domesticated Capsicum spp. and close relatives are well documented by Pickersgill (1980). Two groups have been distinguished, the white- flowered species, including the domesticated C. annuum, C. fratescens, and C. baccatum, and the purple-flowered species, with C. pu- bescens as the main representative. In gen- eral, crossing barriers exist only between the species of these two groups. It is not known which part in the process of fertilization or embryo development is inhibited. More knowledge about these barriers may be help- ful in developing techniques for the in- trogression of genes from the purple-flowered