Selected breeding lines and cultivars of tomatoes (Lycopersicon esculentrum Mill.) were evaluated for heat tolerance in the greenhouse (39°C day and 28°C night) and field using flowering, fruit-set, yield, fruit quality, and seed production as criteria. Under high temperature, heat tolerant lines performed better than the other two groups in all evaluation criteria except for seed production. The opposite was found under normal field conditions where heat sensitive commercial cultivars outyielded the heat tolerant lines and cultivars. Production of viable seeds under high temperature was severely reduced regardless of the heat tolerance level exhibited by the line or cultivar. Some of the heat tolerant lines could provide valuable sources of plant material for physiological studies to establish the molecular basis of heat tolerance and also could provide excellent germplasm sources for breeding heat tolerant tomato cultivars.
Aref A. Abdul-Baki
Marietta Loehrlein and Sandy Siqueira
Coreopsis rosea is important as a landscape plant and is of some impor-tance for restoration of native species. In both situations it is important to understand the breeding system so that the pollination process may be controlled for optimal seed production. The study of the incompatibility system is important to seed production. In commercial crops, seeds may be products of open pollination or F1 hybrids. In the former, genetic variability exists. In conservation and recovery programs of local flora, seeds with genetic variability are desirable. In development of commercial crops, uniform seeds and plants are desirable. Regardless of whether seeds will ultimately be used for commercial crops or for species restoration, an understanding of self-incompatibility will allow the pollination process to be manipulated for optimal seed production. The purpose of this research was to investigate the sexual reproduction mode in Coreopsis rosea. The objectives were to determine whether Coreopsis rosea operates with a self-incompatibility system, and, if so, to discover whether it is a sporophytic or gametophytic mode. The sporophytic form of self-incompatibility has been found in other plants in the Asteraceae family, but no one has studied self-incompatibility in Coreopsis rosea. The purpose of this research was to identify the self-incompatibility system in Coreopsis rosea. A series of self- and cross-pollinations were made in situ, and in vivo pollinations were made and the pistils studied under the microscope. Results indicate that Coreopsis rosea is self-incompatible and operates under the sporophytic mode.
Mark W. Farnham and Howard F. Harrison
The discovery that broccoli (Brassicaoleracea L., Italica Group) sprouts contain high levels of sulforaphane, a constituent that may provide chemoprotection against certain carcinogens, has stimulated much interest in seed production of this crop. Studies were undertaken to determine the potential for producing broccoli seed using self-compatible selections from open-pollinated (OP) populations or doubled-haploid (DH) programs. In all outdoor and greenhouse trials, three OP selections and seven DH lines produced selfed seed, but seed weight per plant and number per plant varied significantly among the entries. In all environments there were individuals with relatively high (i.e., >3 g/plant) production that were significantly different from low (i.e., <2 g/plant) producers. The relative productivity of some lines varied greatly between experiments, which indicates that seed production of particular genotypes is affected differently by environmental conditions. This indicates the importance of identifying lines that are high producers of selfed seed across different environments. Two OP cultivar-derived lines (USVL102 and USVL104) and two DH lines (USVL062 and USVL093) were identified that consistently produced relatively high yields in greenhouse and screen cage trials. These lines are good candidates for evaluating seed production in field tests and as possible sources of seed for sprouting.
Douglas C Needham and Homer T. Erickson
Mean seed production in tetraploid × diploid crosses of Salpiglossis sinuata R et P. was similar to that in diploid × diploid crosses, but germination of the resultant triploid seeds was low (8%). Parental line selection resulted in some germination improvement. Triploid hybrids from these crosses were vigorous, with floral characteristics resembling tetraploids. The fertility indices of self-pollinations of triploids and pollinations by diploid and tetraploid plants were <1, 22, and 6, respectively, compared with 176 for diploid × diploid crosses. Thus, the self-pollinated triploids were virtually sterile.
Vincent A. Fritz, Harold A. Cloud, Robert F. Deef, and Alicia M. Borowski
An experimental research seed dryer based on the heat pump principle was built to dry sweet corn (Zea mays var. rugosa L.) seed on husked ears. The dryer is not susceptible to environmentally induced drying rate fluctuations that are common with a conventional open-system forced-air oven. The dryer operates as a closed system and, as a result, provides a more constant drying environment. The ability to control air flow, temperature, and humidity makes the dryer a valuable tool for seed production research.
Cecil Pounders, Sandra Reed, and Margaret Pooler
Crapemyrtle (L. indica and L. indica × L. fauriei hybrids) is one of the most popular flowering landscape plants in the U.S. Although many cultivars have been developed through breeding efforts, little has been published on the reproductive biology of the genus. The objective of this study was to evaluate barriers to successful self-seed production in crapemyrtle. Self-compatibility was assessed by comparing pollen tube growth, fruit and seed production, and seed germination following controlled self- and cross-pollinations. Observations of pollen tube growth at intervals up to 24 hours after self- and cross-pollination indicated no barriers to self-fertilization acting at the stigmatic or stylar level in L. indica, L. fauriei or cultivars derived from inter-specific hybrids of these two species. Self-pollinations of `Catawba', `Whit IV', `Tonto' and `Tuscarora' had lower percent seed pod set and seed germination than did cross-pollinations of these cultivars. The number of seeds per pod was lower when `Catawba', `Whit IV' and `Tuscarora' were self-rather than cross-pollinated, but no difference between `Tonto' self- and cross-pollinations was observed. When decreased pod set is combined with much lower seed germination for self-pollinations, selfing of crapemyrtle is extremely unproductive when compared to cross-pollination. A late-acting self-incompatibility system or inbreeding depression is indicated for L. indica and inter-specific crosses with L. fauriei.
Anatoli Dzhurmanski, Georgi Dzhurmanski, and Valtcho Jeliazkov (Zheljazkov)
Leuzea, or Maralroot, is a perennial medicinal plant originating from Siberia, and is characterized with significant metabolic and tonic effects. A 3-year study was conducted at the Research Institute for Roses, Aromatic and Medicinal Plants Kazanluk, Bulgaria, on the introduction of various genotypes of Leuzea (Rhaponticum carthamoides Willd/Iljin.) from the Altai region, Russia. Phenological observations, and up to 11 morphological indices were characterized for 1-, 2-, and 3-year-old plants. Generally, it was found that the climatic and soil conditions in the region were not very favorable for the growth and development of Leuzea. Also, for the tested region, Leuzea should be grown only under irrigation. Yields of Leuzea roots and rhizomes reached 7.19 t/ha in the 2nd year, and up to 8.62 t/ha in the 3rd year. Yields of aboveground herbage were up to 8.73 t/ha when plants were harvested at the beginning of blossoming. Second cut of the above-ground herbage of Leuzea was not satisfactory under the climatic conditions of the region. When grown for seed production, seed yields during the 3rd year were up to 128 kg/ha. Leuzea may have a potential as a cash crop for the region if grown for seed production.
Marietta Loehrlein and Sandy Siqueira
Landscape and garden use of Coreopsisrosea has been growing recently. With the introduction of the new varieties of Coreopsisrosea `Sweet Dreams' and `Limerock Ruby', there are increased opportunities for commercial sales. While plants can be propagated by vegetative means, seed production is generally less expensive, seed can be stored, and hybrid development depends on seed production. As a result, it is beneficial to understand the reproductive process of the plant. The purpose of this research was to investigate the reproductive development of Coreopsisrosea. This research also seeks to identify, describe and record inflorescence morphological characters, which could be useful in plant systematic and phylogeny studies. To this end, the anthesis process of pink tickseed, Coreopsisrosea Nutt., was studied in 100 inflorescences from 10 plants. Inflorescences were tagged when they were first visible and measured daily for a month. The following measurements were taken: number of ray flowers, inflorescence diameter, diameter of the disc floret cluster (head), timing of anthesis, presence of pollen, and the longevity of opened flowers. The inflorescence anthesis process was 19.8 (±1.6) days long and was subdivided into 13 stages of development. During the 20 days of inflorescence anthesis, the flower was open 27.5% of the time (5.4 days). When the disc florets started to open, they did so from the outer layer of the cluster to the center of the cluster; therefore, florets in the head did not mature at the same time. Micrographs were taken using a dissecting microscope (Cobra dynascope) to illustrate the entire process.
Laura C. Merrick
Cucurbita argyrosperma, formerly known as C. mixta, is a squash species native to Mexico and Central America. Cultivars of the species which have been grown in the United States include many of the cushaws and the `Silverseed Gourd. A recent biosystematic analysis-which included studies of experimental and natural hybridization, isozymatic and morphological variation, ethnobotany, and ecological and geographical distribution-has shown that the closest relative of C. argyrosperma is C. moschata. The data reveal intriguing implications for evolution of the genus as a whole, since the previous hypothesis that C. lundelliana is the progenitor of C. moschata is refuted. A wild ancestor, three cultivated varieties and a feral derivative are recognized within C. argyrosperma. Two of the three cultivated botanical varieties-vars. argyrosperma and stenosperma -have been selected in many regions almost exclusively for seed production. The relatively large seeds are marketed either with or without hulls. The other botanical variety, var. callicarpa, has been selected for both fruit and seed production. Northern cultivars of var. callicarpa arc notable for their adaptation to marginal environments, including hot climates and poor soil conditions.
R.G. Fjellstrom, D.E. Parfitt, and G.H. McGranahan
1 Present address: U.S. Dept. of Agriculture-Agricultural Research Service, National Forage Seed Production Research Center, Corvallis, OR 97331. This research was funded in part by the California Agricultural Experiment Station, the California