Ornamental Breeding Program Research Articles

The first high-quality genome assembly and annotation of Lantana camara, an important ornamental plant and a major invasive species

This study presents the first annotated, haplotype-resolved, chromosome-scale genome of Lantana camara, a flowering shrub native to Central America and known for its dual role as an ornamental plant and an invasive species. Despite its widespread cultivation and ecological impact, the lack of a high-quality genome has hindered the investigation of traits of both ornamental and invasive. This research bridges the gap in genomic resources for L. camara, which is crucial for both ornamental breeding programs and invasive species management. Whole-genome and transcriptome sequencing were utilized to elucidate the genetic complexity of a diploid L. camara breeding line UF-T48. The genome was assembled de novo using HiFi and Hi-C reads, resulting in two phased genome assemblies with high Benchmarking Universal Single-Copy Orthologs (BUSCO) scores of 97.7%, indicating their quality. All 22 chromosomes were assembled with pseudochromosomes averaging 117 Mb. The assemblies revealed 29 telomeres and an extensive presence of repetitive sequences, primarily long terminal repeat transposable elements. The genome annotation identified 83,775 protein-coding genes, with 83% functionally annotated. In particular, the study mapped 42 anthocyanin and carotenoid candidate gene clusters and 12 herbicide target genes to the assembly, identifying 38 genes spread across the genome that are integral to flower color development and 53 genes for herbicide targeting in L. camara. This comprehensive genomic study not only enhances the understanding of L. camara’s genetic makeup but also sets a precedent for genomic research in the Verbenaceae family, offering a foundation for future studies in plant genetics, conservation, and breeding.

Breeding of ornamental orchids with focus on Phalaenopsis: current approaches, tools, and challenges for this century.

Ornamental orchid breeding programs have been conducted to develop commercially valuable cultivars with improved characteristics of commercial interest, such as size, flower color, pattern, shape, and resistance to pathogens. Conventional breeding, including sexual hybridization followed by selection of desirable characteristics in plants, has so far been the main method for ornamental breeding, but other techniques, including mutation induction by polyploidization and gamma irradiation, and biotechnological techniques, such as genetic transformation, have also been studied and used in ornamental breeding programs. Orchids are one of the most commercially important families in floriculture industry, having very particular reproductive biology characteristics and being a well-studied group of ornamentals in terms of genetic improvement. The present review focuses on the conventional and biotechnological techniques and approaches specially employed in breeding Phalaenopsis orchids, the genus with highest worldwide importance as an ornamental orchid, highlighting the main limitations and strengths of the approaches. Furthermore, new opportunities and future prospects for ornamental breeding in the CRISPR/Cas9 genome editing era are also discussed. We conclude that conventional hybridization remains the most used method to obtain new cultivars in orchids. However, the emergence of the first biotechnology-derived cultivars, as well as the new biotechnological tools available, such as CRISPR-Cas9, rekindled the full potential of biotechnology approaches and their importance for improve ornamental orchid breeding programs.

Collecting horticulturally useful traits in the wild: methodology to maximize genetic gain and minimize risk

Many ornamental crops have extremely narrow germplasm bases, e.g., Lilium longiflorum and Pelargonium domesticum. Thus, there is an imperative need for germplasm collection of wild species both of the crop and its relatives. The downy mildew (Plasmopara obducens) outbreak in Impatiens walleriana is a modern example of narrow germplasm risks with economic consequences. The perils of not collecting novel germplasm in species relatives include specific crop production requirements, which could have been eliminated if wild species had been collected at the commencement of ornamental breeding programs. The potential value to be found in collecting wild species of ornamental crop relatives is immensely proportional to the careful planning of collection trips, integration of local experts, serendipity in finding mutant genotypes, and risk management both during collection and thereafter in the breeding, domestication, and selection process. The objectives of this paper are to demonstrate the value of well-planned collecting trips to maximize genetic gain in future breeding and minimize risks in collected plant materials. More than 30 years of plant collecting experience throughout the world (S. Africa, Europe, N. America) and testing these findings with undergraduate students in a plant production course for new crop development are the basis for these recommendations and guidelines. Essential collection procedures include creating a crop ideotype to identify which traits are of importance in the new germplasm. These traits will direct the timing of when to collect, the best location of populations to maximize trait expression in wild populations, and the existence of natural hybrids, rather than collecting only when seeds are produced and implementing targeted (centers of origin, diversity) vs. random collections. Methods of population sampling to maximize genetic diversity, the numbers of genotypes to collect, and minimizing invasion risk also influence potential genetic gain.

Going nuts: continuing a 40-year-old woody ornamental breeding program©

The Rutgers University Woody Ornamental Breeding Program began in 1960 under the direction of Dr. Elwin Orton. He was initially charged to develop a holly (Ilex species) breeding program with the ambitious goal of crossing I. opaca, our native eastern holly, with the English holly, I. aquifolium. The main premise was to develop an improved plant for the holiday cut branch market that expressed the excellent glossy foliage and berry display found on the English holly combined with the cold hardiness and wide adaptation of the American species. Dr. Orton, a scientist trained in classical corn genetics at the University of Wisconsin, accepted this responsibility and put in a tremendous effort to achieve this goal. Unfortunately, however, after over a decade of tedious work, Dr. Orton abandoned the I. opaca × I. aquifolium project, largely due to genetic incompatibilities between the two species. Fortunately, during this time he also did selection and breeding work within I. opaca alone, which yielded several cultivar releases. These include I. opaca ‘Jersey Princess’, ‘Jersey Knight’, ‘Dan Fenton’, Jersey Delight’, and most recently ‘Portia Orton’. All are female except ‘Jersey Knight’, and several have become well known in the nursery and landscape trade especially noted for their excellent dark green, glossy foliage. Besides I. opaca, Dr. Orton also worked with Japanese holly. Ilex crenata ‘Beehive’ was his best known release—a plant selected from more than 21,000 seedlings derived from crossing I. crenata ‘Convexa’ × I. crenata ‘Stokes’. ‘Beehive’ was selected for its mite resistance, cold hardiness, and compact form. In addition, he also released several dwarf forms of the species—‘Green Dragon’ and ‘Dwarf Pagoda’ were the most widely known (Galle, 1997).

COMPARISON AMONG HYBRIDS AND PRE-SELECTED CULTIVARS FOR RESISTANCE TO ETHYLENE IN ORNAMENTAL PEPPERS

There are many factors affecting the post-production phase that determine the quality and extend the shelf life in ornamental plants and flowers. In general, ethylene present during shipping and marketing is one of the most important factors affecting quality of many potted plants. The aim of this work was to compare two hybrids with two cultivars one resistant and another susceptible to ethylene. The plants of four genotypes were grown in greenhouse until 30% of the fruits were ripe. Then the vases were transferred to a room at 25°C with 8-10 µmol s-1 m-2 with white fluorescent light. Afterwards, the vases were transferred to a 60-L container and treated with 10 µl L-1 ethylene for 48 h. Afterwards, the plants were analyzed for number of leaves and fruits abscised at 0 and 144 h after ethylene treatment. The hybrid 76A—BP showed the lowest leaf abscission compared to the resistant cultivar. The hybrid DRA—BP showed no difference and was similar to the resistant cultivar. For the fruit abscission, there was no significant difference among the hybrids and cultivars. These hybrids will be used in the ornamental breeding program of Capsicum at the Federal University of ParaA­ba and Federal University of ViA§osa.

MAPPING OF DISEASE RESISTANCE IN ORNAMENTALS: A LONG HAUL

Although disease control is of importance in ornamental production, breeding efforts to reach higher levels of resistance in most ornamental breeding programs have been relatively limited. If resistance is considered as a selection criterion it is often used at a relative late stage in the breeding process or when cultivars are in the trialling stage. This is due to a number of specific problems related to ornamental breeding such as the many different ornamental crops and ploidy level in a number of the most important ornamentals. Nevertheless, in the last few years a number of new developments have changed the roadmaps for research in the life sciences and also the feasibility of disease resistance mapping and marker assisted breeding in ornamentals. A number of examples of these new developments will be presented as well as some direct applications for disease mapping research in tulip will be shown.

‘Raider Azure’ Mealy Blue Sage (Salvia farinacea var. farinacea Benth.)

Native wildflowers provide a rich germplasm resource for continued plant improvement. Over the past 10 years, native accessions of Salvia farinacea var. farinacea Benth. have been collected and introduced into an ornamental breeding program. Texas Tech University announces the release of a new mealy blue sage cultivar named ‘Raider Azure’. ‘Raider Azure’ is intended for use as a drought-tolerant native ornamental for demanding landscapes. It has been trialed for use as a perennial bedding plant where it has displayed attractive violet–blue flowers and a vigorous growth habit, which is common in this species. The extended bloom period for mealy blue sage suggests the cultivar ‘Raider Azure’ is well suited for full sun bedding displays in a variety of locations.

Molecular Marker Use in Tree Fruit and Woody Ornamental Plant Breeding

Fruit and ornamental breeders were surveyed about their use of molecular markers in either their breeding programs or in their related research programs. Responses were obtained from over 100 fruit and ornamental breeding programs from throughout the world. Of these, less than 50% used molecular markers in their programs. The two most common uses of these markers were for studies in plant identification and diversity. These were followed by the use of markers in developing molecular maps, in discovering molecular tags and/or trying to identify the genes for specific plant traits, for marker assisted selection, and finally, for the elucidation of plant taxonomy. In conclusion, although there is much research in this area, few programs are actually using markers in the context of an applied breeding program. The major reason for this situation is the lack of available markers and the cost of using these markers to screen large numbers of progeny. Those that use markers in their breeding tend to use them to verify the genotype of the parents or confirm the genotype of selected seedlings rather than screen unselected seedlings.

Update on the Ornamental Breeding Program at the University of New Hampshire

The Ornamental Breeding Program at the University of New Hampshire (UNH) was initiated in 1998, aiming to develop new or improved vegetatively propagated cultivars. Initially, breeding focused on Anagallis monelli (Pimpernel). At the time, only one blue and one orange cultivar (`Skylover Blue' and `Sunrise') were grown commercially. Main breeding goals were to develop plants with more compact habit and earlier flowering in the spring. In 2002, the first two UNH cultivars were released as Proven Selections™: Anagallis`Wildcat Blue' and `Wildcat Orange'. We have also developed breeding lines with new pink, violet, lilac, and white flower colors that are currently in industry trials. Studies on genetics, biochemistry, and anatomy of flower color in A. monelli have been performed and molecular studies are in progress. Breeding of Nolana and Browallia started in 2000 and UNH lines are currently in industry trials. Nolana is comprised of over 80 species native to desert areas of Peru and Chile. Only two cultivars, N. paradoxa`Bluebird' and `Snowbird', and interspecific hybrid `Blue Eyes' are currently commercially available. We now have several Nolana species at UNH representing a wide germplasm base. Based on ornamental potential, some species have been selected for breeding, aiming to develop sterile interspecific hybrids. Studies to break seed dormancy to optimize germination rates are in progress, as well as research on floral development, which is being conducted in collaboration with Peruvian researchers. Interspecific hybridizations have been used in Browallia to develop breeding lines with new or improved traits than those available from seed cultivars.

ANCHORED ISSR AS MOLECULAR MARKER TO CHARACTERIZE ACCESSIONS OF JACARANDA MIMOSIFOLIA L. DON.

Anchored inter-simple sequence repeats (ISSR) were used to identify 21 accessions of Jacaranda mimosifolia, collected mainly in Buenos Aires City, and the others in Mendoza, Salta and Jujuy Province and La Plata City, as part of an ornamental breeding program. DNA was extracted and purified from young leaves and amplified by four anchored primers based on dinucleotide repeats with 5' or 3´extension. A total of 42 polymorphic bands, obtained after electrophoresis in agarose gels stained with ethidium bromide, were used to construct a molecular identification matrix. A mean of 12.75 bands per primer were generated, ranging from 140 to 1,400 bp. The genomic relationship of the genotypes was evaluated using Jaccard coefficient, and the dendrogram was constructed using UPGMA linkage method. All the accessions were differentiated by this technique, which showed a range of Resolving Power from 1.2 to 5.721. The anchored microsatellite analysis was shown to be a promising method to identify selected material in a breeding program of J. mimosifolia and with high potential to be applied to other ornamental crops.

Florida Red Ruffles and Florida Irish Lace: Two New Lance-leaf Caladium Cultivars

Two lance-leaf caladium cultivars are to be released from the ornamental breeding program at the University of Florida. `Red Ruffles', whose pedigree is Red Frill × (`Red Frill' × `Candidum Jr.'), has elongated medium red leaves with ruffled green margins. Plants are upright with strong petioles, have leaf blades 25 cm long and 14 cm wide, and attain a height of 61 cm when grown in full sun in the field. Plants have more leaves and are more cold tolerant than `Red Frill', the major red lance-leaf cultivar of commerce. Tuber yields of `Red Ruffles' are similar to `Red Frill' but less than `Rosalie', with production indices of 95.0, 97.8, and 121.0, respectively. Foliage of `Red Ruffles' is more upright and less likely to elongate under reduced light than the other cultivars. `Irish Lace', an F2 selection from a cross of “Candidum Jr.' × “Red Frill', has elongated dark green leaves with heavily ruffled margins, which are etched with a thin red border. Leaf blades are 26 cm long and 8 cm wide and have heavy substance. Plant height is 65 cm in the field. Tuber yields of `Irish Lace' are greater than `White Wing', a major green/white cultivar. Use of a green caladium would be as a border or a mixture with red or white lance-leaf cultivars.