Intergeneric Hybrids between Weigela and Diervilla (Caprifoliaceae)

Abstract

Weigela Thunb. consists of 12 species distributed throughout Northeast Asia. Diervilla Mill. is a closely related genus containing three species endemic to North America. Taxa from both of these genera are important nursery crops. Hybrids between these genera could potentially combine the excellent cold hardiness and adaptability of Diervilla with diverse forms, foliage colors, and flower colors found in Weigela. Prior attempts to create intergeneric hybrids between these genera were unsuccessful and resulted in embryo abortion before seeds matured. To overcome this barrier, ovule culture and micropropagation procedures were used to develop intergeneric hybrids. Cleaved amplified polymorphic sequences (CAPS) analysis was used to verify hybrids. Intergeneric crosses, D. lonicera × W. middendorfiana, D. sessilifolia × W. florida (two clones), and D. lonicera × W. florida were attempted. Crosses of D. lonicera × W. middendorfiana did not produce viable hybrids. From the remaining three crosses, a total of 544 plants were obtained from 1278 ovules. About 85% of the 544 plants appeared very chlorotic or had low vigor, and senesced when transferred to multiplication medium. Only 80 of the 544 plants were successfully maintained in tissue culture, of which 10 have been successfully transferred ex vitro. CAPS analysis indicated that a majority of these plants were hybrids. Further studies are focused on improving tissue culture procedures and other methods to develop tetraploids to increase plantlet vigor and fertility.