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
R.G. Fjellstrom, D.E. Parfitt, and G.H. McGranahan
J. M. Al-Khayri, F. H. Huang, and T. E. Morelock
Regenerated spinach (Spinacia oleracea L.) maintained under a 10-h photoperiod (65 uE m-2 s-1) after an incubation period on a GA-containing medium were induced to flower in vitro. The plantlets were regenerated from callus initiated on MS medium with 2.0 mg L-1 kinetin and 0.5 mg L-1 2,4-D and were subsequently transferred to a medium containing 2.0 mg L-1 kinetin, 1.0 mg L-1 GA, and 0.01 mg L-1 2-4,D. While on the regeneration medium, the cultures were exposed to a long-day photoperiod. Regenerants were transferred to an IBA-containing medium for rooting, after which flowering was observed. In vitro flowering plantlets exhibited male and female flowers depending on the sex of the explant donor. Female plantlets developed seeds in the culture vessels. This method of seed production from regenerants can eliminate time-consuming steps in acclimation, transplanting to soil, and plant maintenance.
Kanti M. Rawal and Keith Redenbaugh
Polygalacturonase (PG) is the principal enzyme responsible for the softening of tomato during ripening. Transformation of tomatoes with antisense PG (asPG) results in significant delay in softening so that fruits with color and flavor can be harvested and shipped from the fields to distant markets. Safety evaluations of the genetically engineered tomato varieties were conducted from two perspectives: a) agricultural, and b) human food. Data were submitted to the appropriate agencies to obtain approvals for commercial production and to seek advisory opinion for the safety of food for human consumption. Calgene Fresh Inc. was created to develop human resources, physical facilities and logistic capabilities for year round supply of high quality branded produce. Vertical integration from seed production to direct consumer marketing is necessary to optimize the business endeavor.
Michael N. Dana and Ricky D. Kemery
Interest in direct-seeding establishment of wildflowers as a component of landscape planting has continued to increase. Seed may be very expensive. Information is needed on the quality of seed available to consumers and the landscape industry. The goal of this work was to assess the level and consistency of seed quality available from the wildflower seed production/marketing industry. Eleven species of native prairie forb wildflowers and eight species of “garden” wildflowers from seven companies were purchased in 1992 and 1993 and subjected to germination testing. Germination procedures were those of AOSA where available, or generalized from the literature when no guidelines existed. Results showed significant variation among wildflower species, among companies supplying the same species, and over the two seed years tested in the study. These data reinforce the need for seed quality testing and reporting as a part of the sales of wildflower seed.
Bruce M. Pollock
The book, Agricultural Biotechnology: Issues and Choices Information for decision Makers, from USDA and Land Grant Colleges discusses risk evaluation for the use of legislators concerned with public policy. However, that discussion is entirely theoretical. The 1970 epidemic of Southern Corn Leaf Blight caused by the pleiotropic gene for Cytoplasmic Male Sterility provides material to use in real-world risk evaluation for biotechnology. Approximately 1×1012 corn seeds are planted annually in the US. Assuming a mutation rate of 1×10-6, then 1×106 mutations can be expected annually. The poster will evaluate the importance of this number using assumptions based on fold-increase during seed production. Unfortunately, it is not possible to evaluate the risk of incorporating another pleiotropic gene into commercial crops because insufficient data are available on the frequency of pleiotropy.
Michael E. Compton, D.J. Gray, and G.W. Elmstrom
Tetraploid individuals were identified among plants regenerated from cotyledons of diploid watermelon [Citrullus lanatus (Thunb.) Matsum. & Nakai] cultured in vitro. Tetraploid and diploid plants were distinguished by counting the number of chloroplast per guard cell pair. The mean number of chloroplasts was 19 and 11 for tetraploid and diploid plants, respectively. Self-fertile tetraploids were obtained from the diploid cultivars Mickylee, Jubilee II and Royal Sweet. `Dixielee' and `Minilee' tetraploids failed to set fruit. Progeny obtained from self-fertile tetraploids were crossed with diploid pollinators to produce triploid hybrid seed. All triploid plants produced seedless fruit that was superior or equal to fruit produced by currently available triploid hybrids. This demonstrates that tissue culture can be used to produce high quality tetraploid plants for use in triploid hybrid seed production.
Jianhua Zhang and Miller B. McDonald
Varietal identification of cyclamen and petunia is important for flower seed production because these crops are marketed as hybrids and genetic purity determinations assure the purity of the seed lot and the success of hybridization. Random amplified polymorphic DNA (RAPD) banding patterns have been shown to be useful in identifying genotypes of various crops. This molecular biology technique was applied to five commercial cyclamen and six petunia hybrids. Using bulk seed/seedling samples, the varieties could be differentiated. However, when individual seeds of the cyclamen hybrid were tested, differing polymorphisms were observed. These variations were attributed to genetic variability in the inbred parents. We conclude that the genetic purity of cyclamen seeds can be improved and that the use of RAPDs can assist breeders of hybrid flowering crops in better monitoring seed quality.
Erik J. Sacks and Dina A. St. Clair
The influence of cryogenic pollen storage on fruit set and seed production in tomato (Lycopersicon esculentum Mill.) was investigated. Flowers pollinated with pollen samples stored for 5 weeks at –80C, with or without 20 h precooling at 4C, had similar fruit set and number of viable seed per fruit as those pollinated with fresh pollen. Pollen samples, which were repeatedly cooled (–80C) and warmed (to 22 to 24C) for up to six cycles, continuously maintained the same viability as the fresh pollen. When cryogenically stored pollen of L. esculentum 2-837, LA359, LA3198, and LA3199 were used to pollinate LA359, the number of viable seed formed per fruit differed significantly. Results of this study suggest that pollen cryopreservation can be used successfully for tomato breeding and germplasm storage.
Scott Reid, Judy Harrington, and Harrison Hughes
Inland saltgrass, Distichlis spicata var. stricta (Torr.) Beetle, is a native western U.S. grass that has potential in turf situations. Elite clones with outstanding potential have been selected. Poor seed production appears to be the main limiting factor for its use as turf in saline conditions. In order to better understand seed set, 40 genotypes were examined for chromosome number and morphology. Chromosome numbers of root tip metaphase spreads varied with the most common being 2n = 38. However, chromosome numbers of 39, 40, 42, and 74 were also observed. Meiotic examination of anthers revealed 19 bivalents for those with 38 chromosomes while those with 42 had 20 bivalents with 2 unpaired chromosomes. The unpaired chromosomes lagged at anaphase. Crosses among genotypes of different chromosome number have resulted in good seed set. Harvested seed are germinable and plants from these crosses are being grown for further studies.
Most farmers in Sub-Saharan Africa plant local cultivars introduced generations ago. Various national and international organizations and development projects introduce annually hundreds of improved germplasms to a country, and test these under farmer conditions for adaptability and acceptability. Although some local varieties perform well under traditional farming practices, many disease and insect pest resistant improved varieties out-yield local cultivars even under low-input production conditions of Africa. Regrettably, the seed production and distribution system in most of these countries are poorly developed; thus the promising varieties remain unavailable to the majority of farmers. To overcome this problem, the University of Arkansas-led Rwanda Farming Systems Research Project (FSRP) personnel trained farmer-cooperators in the production of good quality bean (Phaselous sp.) seeds. This, and the development of a farmer to farmer seed distribution system that led to quick diffusion of improved bean varieties in the project area will be discussed.