Breeding and genetic manipulation within the genera Buddleja and Trichostema

Recently ornamental and perennial plant breeding has received greater attention as consumers seek out novel plant material. Some genera such as Buddleja L. have been bred for over 70 years however, progress can still be made in areas of molecular, mutagenesis, and hybridization practices to incorporate traits such as flower color, winter hardiness, pubescence, and unique leaf morphology. Other genera such as Trichostema L. have received less attention, so basic breeding experiments would provide information into their genetic relationship.Hybrid production is important to breeding programs, so new populations of hybrid plants were generated in both genera to provide populations for selection and analysis. Within Buddleja, a hybridization experiment to sib-mate a population of B. davidii Franch. 'White Bouquet' x B. indica Lam. hybrids was initiated to assess landscape potential of such hybrids. The population proved to be highly variable for traits such as cold hardiness, number of flowers per panicle, leaf morphology, and resistance to spider mite damage. After three years, four plants remain in evaluation.In another case where B. indica was one of the parents of a hybrid, progeny among a population of hybrid B. davidii 'Empire Blue' x B. indica plants backcrossed to B. davidii 'Empire Blue' were found to be sterile. Since the original parent plant was highly fertile it is thought that the sterility was due to a genic or chromosomal imbalance. Flow cytometric analysis confirmed varying DNA content within the progeny. Morphological traits among this population varied and an increase in panicle length was seen, which would be more desirable to the consumer. Four sterile plants were selected from the population for further evaluation.Within Trichostema, hybridizations among T. arizonicum A. Gray x T. lanatum Benth, resulted in the released selection 'Blue Myth'. 'Blue Myth' was surprisingly sterile halting further hybridization, but the sterility allowed for profuse flowering in the field. Another Trichostema cross between T. purpusii Brandegee. and T. lanatum resulted in fertile offspring. Field evaluation of this hybrid showed a plant with a more compact growth habit but less abundant flower production than the T. arizonicum x T. lanatum hybrids.Experiments to induce polyploidy in Buddleja were carried out on an individual hybrid selection. An oryzalin experiment was set up with a combination of chemical concentration along with varying exposure times. Six confirmed tetraploid plants were generated. Hybridization using these tetraploids confirmed the restoration of fertility and generated a population of plants that were bi-colored. Open pollination of this F1 population did not generate completely orange-flowered hybrids, but did result in the first reported petaloid mutants.Besides hybridization to control unwanted fertility in Buddleja , a regeneration and gene insertion protocol using Agrobacterium was investigated. No transformed plants were developed, which was due largely to not being able to establish an efficient shoot regeneration protocol for B. davidii var. nanhoensis 'Alba' and B. davidii var. nanhoensis 'Mongo'. Factors likely affecting success rate included type of media used, hormone concentrations, plant material, bacterial strain, and selection method.