Regeneration of soybean (Glycine max L. Merrill) through direct somatic embryogenesis from the immature embryonic shoot tip

We describe here a simple and efficient system of soybean (Glycine max L. Merrill) regeneration through direct somatic embryogenesis by using immature embryonic shoot tips (IEST) as explants. The cultivar Kaohsiung 10 (cv. K10) used in this study did not show embryogenic response either from mature seed-derived explants (cotyledon, embryonic tip, leaf, shoot and root) or immature cotyledons. However, it showed a high percentage (55.8%) of somatic embryo (SEm) formation from the IEST excised 2-3 wk after flowering, thus indicating the crucial roles of type and age of explants. The IEST put forth primary SEm after 2 mo of culturing on Murashige and Skoog (MS) medium supplemented with 6% sucrose, 164.8 A mu M 2,4-dichlorophenoxyacetic acid (2,4-D), 5 mM asparagine and 684 A mu M glutamine. Subsequently, secondary SEm were developed 1 mo after culturing on MS medium containing 123.6 A mu M 2,4-D and 3% sucrose. Cotyledonary embryos were induced on MS medium supplemented with 0.5% activated charcoal after 1 mo. The embryos were desiccated for 72-96 h on sterile Petri dishes and regenerated on hormone-free MS medium. Plantlets with well-developed shoots and roots were obtained within 5-6 mo of culturing of IEST. The SEm-derived plants were morphologically normal and fertile. Various parameters thought to be responsible for efficient regeneration of soybean through somatic embryogenesis are discussed. To our knowledge, this is the first report to employ IEST as explants for successful direct somatic embryogenesis in soybean

Forced flowering of pineapple (Ananas comosus cv. Tainon 17) in response to cold stress, ethephon and calcium carbide with or without activated charcoal

Ethylene, a gaseous plant hormone, is responsible for the initiation of reproductive development in pineapple. Reproductive development can be forced in pineapple (Ananas comosus var. comosus) throughout the year with ethylene. Inhibition of natural flowering initiation with aviglycine [(S)-trans-2-amino-4-(2-aminoethoxy)-3-butenoic acid hydrochloride], an inhibitor of ethylene biosynthesis, provides evidence that reproductive development in response to cold stress and short daylength is also in response to ethylene production. We studied the effect of cold treatment of pineapple on ethylene production and flower induction by applying a short-term cold stress to stem apices. Shoot apices of pineapple treated with ice crystals also produced twice as much ethylene as did those of control plants and significantly more than was produced by "D" leaf basal tissue. Moreover, pineapple plants treated four times with ice crystals or ice water were induced to flower under field conditions and the forcing efficiency, as evaluated by the percentages of inflorescence emergence and fruit harvest, was comparable to forcing with calcium carbide (CaC(2)) and ethephon. In another field experiment two applications of a 1.0% solution of CaC(2) or 0.15% ethephon applied at 48 h intervals was sufficient to force reproductive development of 'Tainon 17'. Furthermore, 0.5 or 1.0% solutions of CaC(2) supplemented with 0.5% activated charcoal (AC) significantly improved the forcing effectiveness of CaC(2). This could/would make it possible to reduce the number or concentration, or both, of CaC(2) required to effect forcing in pineapple

Delaying natural flowering in pineapple through foliar application of aviglycine, an inhihitor of ethylene biosynthesis

In Taiwan, the major yield constraint in pineapple cultivation is natural flowering, which occurs when daylengths are shorter and nights are cooler. This natural (precocious) flowering increases the cost of cultivation and reduces the percentage of fruits of marketable size. Two field experiments were conducted to evaluate the inhibitory potential of aviglycine [(S)-trans-2-amino-4-(2 aminoethoxy)-3-butenoic acid hydrochloride, AVG on natural flowering of 'Tainon 17' pineapple plants during the 2003 to 2004 and 2004 to 2005 cropping seasons. In the 2003 to 2004 season, bolting in the control exceeded 80% on 2 Mar. 2004, whereas no bolting was observed in the treatments. Inhibition of bolting by aviglycine (AVG) was dependent on the concentration and frequency of application. Bolting was less than 40% when plants were treated in Nov. and Dec. 2003 with 500 mg center dot L-1 of AVG four times at 15-day intervals or with five applications made at 10-day intervals. For the 2004 to 2005 season, bolting of plants treated with 250 or 375 mg center dot L-1 AVG was delayed 4 weeks relative to the control, whereas bolting was delayed 7 weeks by four or five applications of 500 mg center dot L-1 of AVG applied at 10- or 15-dav intervals. Both experiments showed that four to live applications of 500 mg center dot L-1 of, VG at 10- or 15-day intervals delayed inflorescence emergence relative to the control for the duration of the treatments. We assume control was maintained for 1 to 2 weeks after treatments stopped. Based on these results, the date AVG treatments stop can be used to estimate the duration of delay in flowering. AVG inhibits ethylene biosynthesis and has the potential to be effectively used to delay or completely control the problem of precocious flowering and associated crop losses in pineapple