Carica papaya L. (papaya) single somatic embryos (2.0 mm diameter) produced in a high-frequency liquid production system were encapsulated in two different synthetic encapsulation compounds. The frequency of regeneration from encapsulated embryos was significantly affected by (1) the concentration of sodium alginate, (2) the presence or absence of nutrient salts in the capsule, and (3) the duration of exposure to calcium chloride. A 2.5% sodium alginate concentration in a half-strength MS salts base resulted in significantly higher germination frequencies than other treatments. A relatively short (10 min) exposure to CaCl 2 provided uniform encapsulation of embryos and the highest frequencies of successful germination (77.5%). Germinated artificial seeds produced normal plantlets.

A range of antibiotics and short-term exposure to an acidified (pH 3.0) medium were evaluated for their effects on eliminating Agrobacterium tumefaciens, supervirulent strain EHA101 (pEHA101/pGT100), from leaf explants of `Royal Gala' apple (Malus ×domestica Borkh.) and on shoot regeneration. Exposure of leaf explants to regeneration and elongation media containing 100 μg·mL-1 concentrations of the antibiotics carbenicillin (crb), cefotaxime (cef), and cefoxitin [=mefoxin (mef)], singly or in combination for 52 days did not eliminate A. tumefaciens from the explants. The percentage of regeneration on crb, cef, and mef was 97%, 11%, and 50%, respectively, compared to 67% for the controls. Short-term (1- to 18-hour) vacuum infiltration with 500 μg·mL-1 of any of the above antibiotics did not inhibit regeneration and failed to eliminate A. tumefaciens from leaf explants. Cef (2000 μg·mL-1) did not inhibit the percentage of regeneration and was more effective than crb or mef in preventing growth of A. tumefaciens when vacuum infiltrated into apple leaf explants for 30 minutes. Further experiments demonstrated that the incidence of A. tumefaciens contamination could be reduced to 28% without negatively impacting shoot regeneration by using a 1-hour vacuum infiltration with an acidified medium, an 18-hour vacuum infiltration with cef (5000 μg·mL-1), and a 52-day incubation on regeneration and elongation media containing 100 μg·mL-1 each of mef and crb. Kan resistant, GUS (β-glucuronidase) positive, putative transformants without A. tumefaciens were generated by adding kan (10 μg·mL-1) to the regeneration and elongation media.

The important role that chlorophyll (CHL) plays in plants necessitates its estimation in various types of studies. Singh and Anantrao (6) realized the need for a reasonably simple, rapid, and accurate method of CHL determination capable of accommodating small quantities of leaf tissue and a large number of quantitative estimates in a short time, and thus, in 1937, they developed a photoconductive photometer for quantifying CHL in 80% methanol. Since then, CHL determination techniques have improved considerably, but complete extraction of CHL is laborious, slow, and inconvenient in some plant species (3). Conventional methods used for isolating and measuring chlorophyll in aqueous acetone or similar organic solvents are sometimes cumbersome and slow, and always destructive to leaf tissue (1, 4, 7). Furthermore, steps involved in sample preparation, pigment extraction, and dilution result in pigment loss and contribute to variability. Moran (5) developed an efficient method for extracting small quantities of CHL from intact cotyledons with N,N-dimethyl-formamide (DMF). Inskeep and Bloom (3) further improved this technique by using extinction coefficients of chlorophyll a and b extracted in DMF. Evans (2) extracted CHL in 80% acetone and adapted Amon's modification of the method of McKinney (5), who provided equations (μmol CHL/1 = 22.22 D645 + 9.057 D663) to evaluate the molar concentrations of total chlorophyll (CHL a and b) in the tissue extracts. Nevertheless, these procedures are still time consuming since they require tissue extraction and spectrophotometric measurement. The objective of this investigation was to determine area concentrations of total chlorophyll (CHL a + b) using a portable chlorophyll meter (SPAD-501) and to compare and correlate these data with area concentrations of total CHL obtained by conventional methods.

The 1990 census of the United States revealed a substantial increase in the ethnic diversity of the American population. Federal dietary guidelines recommend that American consumers double their intake of fresh fruits and vegetables. For quite some time, the ethnic diversity of the population and the associated food patterns have been exposing Americans to a panorama of exotic produce from overseas as well as from selected domestic sources (Greene, 1992). The specialty produce industry in the United States is hardly more than 30 years old, but the niche market for these fresh food items is the fastest growing segment of the produce industry (Vietmyer, 1984). Over the last decade, the consumption of produce has increased steadily, whereas the demand for exotic specialties grew exponentially. Consumer awareness of the nutritional value and health benefits of exotics and adventurism to try fascinating and unusual produce and other edibles raise the demand for exotic fruits, vegetables, and other horticultural commodities (Ritchy, 1978). Displays of exotic horticultural specialties are now becoming a mainstay in supermarkets, with specialty themes ranging from the islands of Asia, Latin America, and the tropics, among others. Shipments of tropical produce and goods rose from 2000 t in 1980 to 70,000 t in 1990, and to 680,000 t in 1991, while more than 1,000,000 t of specialty crops were shipped during 1992 and after (Greene, 1992). Americans not only are more health-conscious but also demand more diverse and ethnically flavored foods. With population shifts, changes in diet, and the persistent fascination of Americans with novelty items, the demand for specialty fruits and vegetables likely will continue to rise through the 1990s and beyond. Domestic production to satisfy ethnic demands for exotic or nontraditional horticultural commodities necessitates developing the technologies to grow these crops locally. To accomplish this objective, there is a definite need for systematic horticultural research to generate the required information for cultivation and management of these crops. Ongoing small-or large-scale research projects at several institutions indicate ample enthusiasm among the horticultural community. These trends demonstrate that an overview of current research efforts on these commodities is appropriate at this time. This workshop precisely served that purpose through a structured open forum for researchers in various

No abstract