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- Author or Editor: Anson E. Thompson x
Plants with a compact growth habit have been identified in populations of Cuphea leptopoda Hemsley. The primary morphological effect has been shown to be conditioned by a single recessive gene, designated si for shortened internodes. Short internodes on compact plants result in reduced length of the main stem, reduced number and length of both primary and secondary branches, and reduced flowering resulting from a decrease in number of flowers per node on the main stem and branches. The compact growth habit and more concentrated flowering of the shortened-internode plants may have horticultural and agronomic value in new interspecific hybrids being developed.
In the June 1982 issue of HortScience (2), Cecil Blackwell, Executive Director of the American Society for Horticultural Science, wrote a Viewpoint article strongly supporting an amendment to the ASHS By-Laws establishing an International Affairs Division. He emphasized that the Society's commitments to international horticulture were long-standing and that the purposes of the Society are to promote and encourage national and international interest in scientific research and education in horticulture throughout all its branches. The International Affairs Division officially was established by a vote of the Members at the 79th Annual Business Meeting of the Society held on 12 Aug. 1982 at Ames, Iowa.
Vernonia galamensis (Cass.) Less. (Asteraceae) constitutes a species complex of six subspecies, one of which contains four varieties. Crossing barriers between the subspecies and varieties are being examined. In the analysis of microspore mother cells, no differences in chromosome number (n=9) were found, and meiosis appeared to be normal within and between subspecies. However, an extended delay in time was observed in all subspecies in which chromosomes remained condensed during the post-meiotic tetrad stage. No apparent effect on pollen formation or pollen tube growth was observed from this unusual phenomenon. Self and reciprocal intraspecific crosses are being made, and pollen tube growth into the ovules assessed by fluorescent microscopy. These techniques are being used to characterize self-incompatibility within subspecies and varieties, and to determine the possible barriers to pollen tube growth and autofertility.
Genetic markers have not yet been described for Lesquerella fendleri (Gray) Wats. a potential new industrial oilseed crop. Seeds of this species are also utilized as a primary component in some desert wildflower seed mixes. Allozyme variation was analyzed for aconitase (ACO), phosphoglucomutase (PGM), and phosphoglucose isomerase (PGI). Four codominant loci, useful as markers, were clearly resolved. In an open-pollinated population, an outcrossing rate and pollen gene frequency was obtained from 20 random families, using these loci. This initial estimate indicated that seed production primarily resulted from outcrossing. Male sterility was discovered in six bulk populations derived from single plant selections. The frequency of this trait, which could affect the outcrossing rate, was found to occur in 15 percent of the plants. Additional populations will be analyzed for validation.
Eighteen interspecific hybrids from eight different Cuphea species have been confirmed morphologically and cytologically. Seven hybrids from reciprocal crosses of various accessions of the herbaceous annual C. procumbens (N = 9) and the semiwoody perennial C. llavea (N = 9) exhibited a relatively high degree of fertility. Some hybrids have horticultural potential and are currently undergoing evaluation as new pot or bedding plants. Other hybrids that are sterile due to meiotic irregularities are: C. procumbens (N = 9) × C. crassiflora (N = 12); C. procumbens (N = 9) × C. leptopoda (N = 10); C. procumbens (N = 9) × C. leptopoda (N = 8); C. procumbens (N = 9) × C. lanceolata (N = 6); C. lanceolata (N = 6) × C. llavea (N = 9); C. lanceolata (N = 6) × C. lophostoma (N = 8); C. leptopoda (N = 10) × C. laminuligera (N = 10); C. procumbens (N = 9) × C. caesariata (N = 18); and C. lanceolata (N = 6) × C. caesariata (N = 18). C. leptopoda × C. laminuligera is of considerable interest, because it is the first successful interspecific hybrid between species in different fatty acid groups. A relatively fertile amphidiploid of C. leptopoda × C. laminuligera was induced by colchicine. Seed has been produced by self-pollination of the amphidiploid and attempts are being made to backcross the hybrid to the original parents.
Lesquerella fendleri (Gray) Wats. (Brassicaceae) is a potential oilseed crop with many commercial applications, primarily as lubricant additives, but also in resins, waxes, plastics, and cosmetics. This species is native to the southwestern United States where new populations have been collected over the past 2 years to increase germplasm diversity for plant breeding. Some of these new accessions were evaluated and seeds increased at Phoenix, Ariz., over the 1994–95 season. Measurements of stand establishment; plant height and width; leaf, shoot, and flower characteristics; and growth habit were taken over the season. Plants were also examined for autofertility and male sterility. Seed-oil characteristics, seed size and yield, glucosinalate content, and seedcoat gum content will be measured at harvest. Plant descriptors for Lesquerella have been developed as a result of these measurements. Following seed increase, germplasm will be entered into the National Plant Germplasm System. This information will be useful in determining the most promising material for plant breeding.
Five interspecific Cuphea hybrids were examined for isozyme banding patterns. In three of the five hybrids (C. viscosissima × C. lutea, C. ignea × C. angustifolia, and C. lanceolata × C. viscosissima), F1 plants could be distinguished from either parental species. Phosphoglucomutase and 6-phosphogluconic dehydrogenase enzyme stains produced distinct F1 band patterns for all three hybrids. Phosphoglucose isomerase and shikimate dehydrogenase enzyme stains produced distinct F1 band patterns for C. viscosissima × C. lutea and C. lanceolata× C. viscosissima, respectively. For the C. lanceolata × C. viscosissima hybrid. the banding patterns were used to identify 32 selfs among 161 putative F1 plants.
Leaf intumescences of 16 Cuphea species were evaluated in three greenhouse tests. Cuphea crassiflora S.A. Graham had the greatest severity of leaf intumescences followed by C. tolucana Peyr. and C. wrightii A. Gray. Cuphea koehneana Rose, C. inflata S.A. Graham, C. lanceolata Ait., and C. leptopoda Hemsley had fewer than 10% of the leaves with intumescences. Cuphea carthagenensis (Jacq.) Macbr., C. glutinosa Chamb. & Schldl., C. hookeriana Walp., C. paucipetala S.A. Graham, and C. procumbens Gomez O. were free of leaf intumescences. Leaf intumescences for C. wrightii ranged from 100% for seed accession number A0243 to 0% for seed accession numbers A0378 and A0305. White flies (Trialeurodes vaporariorum Westwood) did not contribute to leaf intumescences development.
Vernonia galamensis is a potential new crop for production of epoxidized oil with many industrial applications. This plant is native to equatorial Africa, and not adapted for culture in temperate zones since it requires a short daylength to initiate flowering and subsequent seed development. One collection of V. galamensis ssp. galamensis var. petitiana, flowered freely and produced seeds during long-day conditions throughout the United States. This variety lacks important plant characters for successful commercialization. The favorable genetic recombination of day-neutral response with more desirable plant growth characteristics, desirable seed oil and fatty acid content from other accessions of V. galamensis has been accomplished in hybrids and segregating populations, and selections are being widely evaluated throughout the U.S..