Interspecific hybridization, ploidy manipulation, and cytological and genetic analyses as tools for breeding and improvement of Callicarpa L., Cryptomeria D. Don, Hibiscus L., and Tecoma Juss
Contreras, Ryan Nelson
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Research was conducted as part of breeding programs to improve Callicarpa, Cryptomeria, Hibiscus, and Tecoma including field evaluation, polyploidization, genetic and cytogenetic studies, and interspecific hybridization. These techniques were successfully integrated into existing improvement programs. Polyploidy was induced in Hibiscus acetosella ‘Panama Red’ PP20121 to develop a more compact plant. Plant height and fertility was reduced, leaves were smaller, internodes were shorter, and canopy volume were reduced in the induced octoploid. Japanese cedar chromosomes were doubled by spraying seedlings with oryzalin. Eighty-three percent of selected seedlings were tetraploids, 9.3% were cytochimeras, and 7.6% were diploids. Performance of Japanese cedar cultivars was evaluated by measuring chlorophyll and carotenoids and assigning color ratings. There were differences in chlorophyll, ratio of chlorophyll a:b, carotenoids, and color rating (greeness). There were no consistent trends for differences between winter and summer or between traits. Crosses were performed to investigate the genetics of fruit color, leaf variegation, self-compatibility, and apomixis in American beautyberry. Crosses between purple and white fruit showed white fruit is recessive and is controlled by a single recessive gene called white fruit (wf). Progeny developed sexually and all genotypes were self-compatible. We propose that purple, pink, and white fruit are allelic with proposed symbols Wf > wf p > wf. Maternal effects appear to be involved in leaf variegation; however, germination was too low to draw conclusions. Callicarpa americana seeds were treated with sulfuric acid to increase germination. The control, 15 min, and 30 min treatments germinated at 8.9%, 57.8%, and 48.9%, respectively, indicating that scarification benefits germination. Genome sizes of Callicarpa were calculated using flow cytometry and ranged from 1.34 to 3.11 pg. Chromosome counts revealed most were diploid (2n = 2x = 34) but two were tetraploid. Interspecific hybridization in Tecoma was conducted. Fertile hybrids between T. garrocha and T. stans (F1) were backcrossed to parents and self-pollinated. Tecoma garrocha, T. stans, and T. guarume ‘Tangelo’ were self-fertile. Complex hybrids were developed: F1 x T. capensis; F1 x T. guarume ‘Tangelo’. Leaf morphology of F1 was intermediate. GISH successfully identified hybridity. Four copies of rDNA were observed in F1s using FISH.