Recent emphasis on restoration of degraded wetland and riparian areas in the Intermountain area has created a demand for planting stock of native sedges (Carex spp.) and rushes (Juncus spp.). There are ≈ 100 native sedges and 20 rushes in this region, few of which have been propagated in the past. Many grow in moist to wet areas and are adaptable to water gardens. Some are upland species, capable of growing in drier areas and landscape plantings. Members of both genera are easily propagated vegetatively, but there is increasing interest in seed propagation of these species, with nurseries installing seed production blocks of common sledges. Longevity of sedge and rush seed in sealed, dry storage is unknown, but we have noted little or no viability loss in 15 species after 3 years of storage. Viability testing is used to estimate seed quality because rules for testing seeds of each species are not yet available. Researchers are beginning to examine germination requirements of individual species. Germinability and dormancy vary widely among species and seedlots, but germination is frequently improved by exposure to light and alternating incubation temperatures. Developing seedlings grow rapidly, producing dense, fibrous root systems.
Nancy L. Shaw and Emerenciana G. Hurd
Richard W. Robinson
Bumblebees are commercially used to improve fruit set of greenhouse tomatoes, but they seldom pollinate tomatoes outdoors if not confined in a no-choice situation. Bumblebees frequently pollinated L. peruvianum and other self-incompatible (SI) Lycopersicon species, but not tomato plants, in the field at Geneva, N.Y. Bumblebees were very efficient pollinators of Sl Lycopersicon species, averaging only 5 s to pollinate one flower and fly to the next. Transfer of this attractiveness to pollinating insects to the tomato could improve fruit set of tomatoes grown in greenhouses with introduced bumblebees. It could also improve fruit set in the field, especially when conditions are poor for pollination. It has potential use for producing F1 hybrid seed, but associated problems make hybrid tomato seed production by insect pollination impractical now. Attractiveness to pollinating insects is being introgressed from L. peruvianum, L. hirsutum, and L. pennellii in the tomato breeding program at Geneva, N.Y. Several floral characteristics were found to be of importance for attracting pollinators, including the reaction to ultraviolet light. Flowers of SI species absorbed UV, whereas tomato flowers reflected UV light.
Jonathan R. Schultheis, Wanda W. Collins, and Charles W. Averre
Micropropagated sweetpotato is utilized in California as pan of its seed production program. Sweetpotato yields and quality might be improved in North Carolina by incorporating micropropagation as pan of its plant production scheme. Field studies were conducted in 1992 and 1993 to determine the effects of micropropagation, virus, and hill selection on yield and qualify of Jewel and Beauregard varieties. In 1992, yield was increased in Beauregard with micropropagated plants compared with plants that were derived from the North Carolina seed program. However, no yield advantage was measured when Jewel was micropropagated. In 1993, yield from micropropagated Beauregard sweetpotato plants was the same as when plant material was derived from the North Carolina Certified Seed program. Virus-free micropropagated Beauregard plants yielded more number one and canner grade roots than micropropagated plants that harbored the virus at planting. Russet crack symptoms were significantly greater in roots that were not micropropagated compared with micropropagated plants. Total marketable yield of Jewel was increased when obtained from micropropagated versus nonmicropropagated plant stock. Micropropagated Jewel obtained from a California selection yielded nearly 20% less than the North Carolina selection. Yields from micropropagated planting stocks consistently were equal to or better (typically 10 to 20%) than from plant stock not micropropagated.
S.C. Myers and A.T. Savelle
`Guardian' peach rootstock has shown improved survivability in areas where root-knot nematode and peach tree short life are a problem. Many peach rootstocks are typically propagated from seed. Availability of seed may vary and the long-term genetic uniformity of rootstock material may be difficult to maintain due to out-crossing during seed production. A reliable, successful vegetative propagation method would potentially increase the rate at which material could be made available and more closely ensure genetic uniformity. Production of liners was compared between rooted cuttings and seed of mature `Guardian', `Lovell', and `Nemaguard' peach trees. Seed were stratified under uniform conditions, planted at initial germination, and seedling emergence recorded 30 days after planting. Terminal softwood and semi-hardwood cutting were treated with KIBA and rooted under intermittent mist in a greenhouse. Rooting percentage was equal to or greater than percent seedling emergence. Optimum results were obtained with semi-hardwood cuttings taken in July and August. Rooted cuttings transplanted to the field produced liners of equal or greater quality than liners produced from seed. Seedlings exhibited variability in growth in the nursery area. Rooted cuttings had fewer lateral branches in the lower 15 cm of rootstock where trees were T-budded with certified, virus-indexed buds of `Cresthaven' peach.
Civil war and the hostilities which followed it in Cambodia from 1972 to 1979 resulted in a 20% reduction in the country's population and the near total destruction of its educational and agricultural research infrastructure. As if this were not enough, western governments embargoed humanitarian aid to Cambodia during its most critical period of need from 1981 until multiparty elections were held in 1993. During this period a handful of nongovernmental agencies helped the government begin rebuilding some of its agricultural production capacity. One NGO, together with its government counterparts, established the country's first research station for vegetable crops in 1985 at the request of the Ministry of Agriculture. The Kbal Koh Vegetable Crops Research Station was built and its staff received training from 1985 to 1987. The facility has continued its four-part mission with very limited outside funding and technical support since 1987. Numerous variety and seed production trials have been conducted at the station and in farmers' fields since 1985; practical training programs for agricultural technicians and students began in 1986 and today provide much of the salary and operating budget support for the station. Coinciding with the phase out of NGO assistance in 1995, their are great expectations for continuing support through the newly formed Cambodia–Laos–Vietnam vegetable production and research network, AVRDC, and the Asian Development Bank.
Jennifer A. Gargiulo and Michael E. Kane
The genus Cryptocoryne (Araceae) contains some of the most commercially important amphibious species used in the aquarium plant trade. However, seed production is rare and vegetative propagation by rhizome division is extremely slow. Procedures for in vitro establishment, axillary shoot proliferation and plantlet acclimatization of Cryptocoryne Becketti Thwaites ex Trimen were determined. Surface sterilized rhizomatous shoot tips were established on a medium consisting of Linsmaier & Skoog mineral salts and organics supplemented with 87.6 mM sucrose, 2.2 μM benzyladenine (BA) and 0.57 μM indole-3-acetic acid (IAA) solidified with 0.8% TC® Agar. Effects of medium supplementation with factorial combinations of BA (0 - 25 μM) and IAA (0 - 10 μM) on axillary shoot proliferation from single node explants were determined after 28 days. Maximum axillary shoot proliferation (`l-fold increase) occurred on medium supplemented with 25 μM BA and 1.0 μM IAA. Excellent microcutting rooting (100%) was achieved by direct sticking in Vergro Klay Mix A. Greenhouse acclimatization of rooted microcuttings was 100%.
Ingrith D. Martinez and P.M. Lyrene
Fruit set, fruit size, and seed production after hand pollination in a greenhouse were compared for southern highbush blueberry managed in two ways: a) 69 clones were allowed to go dormant and lose their leaves in the field before being dug and subjected to 1000 hours at 5 °C and b) 26 clones were kept growing in a greenhouse through fall and winter without leaf loss and without chilling, to induce flowering on plants that had mature leaves. On each plant in both management systems, some flowers were self-pollinated, some were cross-pollinated, and others had the styles removed before anthesis to prevent pollination. For >1000 flowers per pollination treatment on the deciduous plants, fruit set averaged 1% for no pollination, 46% for self-pollination, and 76% for cross-pollination. The corresponding values for the evergreen plants were 23%, 59%, and 81%. Parthenocarpic berries averaged 0.37 g/berry for deciduous plants and 1.01 g for evergreen plants. Both crossed and selfed berry weights averaged slightly higher for the evergreen plants than for the deciduous plants, but seed number per berry was much lower for the evergreen plants (12 seeds in crossed berries and four seeds in selfed berries) compared to deciduous plants (37 and 8). Southern highbush blueberry plants that flower without going dormant appear to have much higher parthenocarpic capabilities than those that flower after a dormant period.
J. Frick and C.A. Mitchell
Due to its short time to flower (14-18 days) and rapid maturation cycle (50-55 days), dwarf rapid-cycling brassica (Brassica napus) is under consideration as a candidate oilseed crop for NASA's Controlled Ecological Life Support Systems program. Recent work has focused on defining a set of optimum environmental conditions which permit increased crop yield in terms of g·m-2d-1 of edible biomass. A wide range of environmental variables have been considered including lamp type, CO2 level, nutrient solution pH, and planting density. In addition, nitrogen nutrition regimes have been manipulated with respect to nitrogen concentration (2 to 30 mM), source (NH4 + and/or NO3 -), and time of stepwise changes in nitrogen level (day 14 to 28). The highest seed oil content (42% DW basis) has been found under limiting nitrogen levels (2 mM). However, the low nitrogen inhibits overall seed production potential. Different cultural techniques also have been compared, including solid-substrate, passive wicking hydroponics versus liquid culture systems. Trials are underway to assess crop growth and development under the “best set” scenario of environmental conditions. At present, the highest seed yield (10.6 g·m-2d-1) has been obtained using solid-substrate hydroponic systems under a combination of metal halide and high-pressure sodium lamps. Constant CO2 enrichment to 1000 μmol·mol-1 did not increase crop yield rate.
Research supported in part by NASA grant NAGW - 2329.
Mark W. Farnham, Katherine K. Stephenson, and Jed W. Fahey
Broccoli (Brassica oleracea L., Italica Group) seed and resulting sprouts can contain high levels of glucoraphanin, a glucosinolate, which can be converted to sulforaphane, a compound with cancer protective and antioxidant properties. This observation has stimulated interest in broccoli seed production. In this study, inbred lines, which produce relatively high yields of homogeneous, selfed-seed across different environments in the absence of insect pollinators, were used to evaluate the relative importance of genotype versus environment as a determinant of glucoraphanin concentration in broccoli seed. Glucoraphanin and glucoiberin were measured in broccoli seed lots generated from ten broccoli inbred lines grown in two greenhouse and two screen cage environments. Typically, seed glucoraphanin level ranged from 5 to 100 μmol·g-1 seed and glucoiberin ranged from 0 to about 40 μmol·g-1 seed, regardless of the environment in which seed was produced. Analysis of variance indicated that genotype was the most significant factor influencing levels of the two glucosinolates. Although significant environmental and genotype × environment effects were observed for glucoraphanin and a significant genotype × environment effect was observed for glucoiberin, these effects were small compared to the genotype effects. Results indicate that it is possible to identify broccoli inbreds that consistently produce relatively high yields of seed with a high glucoraphanin content across different environments.
David M. Czarnecki II, Zhanao Deng, Madguhuri N. Rao, Frederick G. Gmitter Jr., Young A. Choi, Jeffrey G. Norcini, and David G. Clark
As one of the Florida's state wildflowers, Coreopsis leavenworthii is highly desirable for roadside plantings in all parts of the state. Seeds of this species are being produced by growers. Where should seed be produced for different ecotypes? Where can the seed be used? These are among questions that have arisen in commercial seed production and distribution. To address these questions, it was necessary to assess the levels of genetic diversity. Eleven populations (242 total individuals) were collected from different parts of Florida, grown at one location in central Florida, and observed for morphological variations. North Florida natural populations had more complex leaves, while south Florida natural populations had smaller flowers. Principal component analyses revealed that two of the seven characteristics studied accounted for as much as 88% of the morphological variations observed. Molecular diversity was analyzed by using the fluorescent amplified fragment length polymorphism (AFLP) technique and the capillary sequencing system. Four primer combinations detected 320 AFLP fragments, of which 90.6% were polymorphic. The overall genetic diversity in the species was 0.2206 (estimated using AMOVA), of which 77.9% was within populations and 22.1% was among populations. The genetic distance among populations seemed to be loosely correlated with geographical distances. A high level of gene flow was found in several populations. Based on the results, a model has been developed to describe the genetic relationship of Coreopsis leavenworthii populations.