Optimal protocol for efficient genetic transformation has been defined to aid future strategies of genetic engineering in pigeon pea with agronomically important genes. Transgenic pigeonpea plants were successfully produced through Agrobacterium tumefaciens-mediated genetic transformation method using cotyledonary node explants by employing defined culture media. The explants were co-cultivated with A. tumefaciens strain C-58 harboring the binary plasmid, pCAMBIA-1301 [con-ferring $\beta$-glucuronidase(GUS) activity and resistance to hygromycin] and cultured on selection medium (regeneration medium supplemented with hygromycin) to select putatively transformed shoots. The shoots were then rooted on root induction medium and transferred to pots containing sand and soil mixture in the ratio of 1:1. About 22 putative TO transgenic plants have been produced. Stable expression and integration of the transgenes in the putative transgenics were confirmed by GUS assay, PCR and Southern blot hybridization with a transformation efficiency of over 45%. Stable integration and expression of the marker gene has been confirmed in the TO and T1 transgenics through PCR, and Southern hybridization.

Development of efficient plant regeneration and genetic transformation protocols (using the Particle Inflow micro-projectile Gun and the shoot-tips as target tissue) of Sorghum bicolor (L.) Moench in terms of expression of the reporter gene, $\beta$-glucuronidase(uidA) is reported here. Two Indian cultivars of sorghum were used in the study, viz. M-35-1 and CSV-15. Plant regeneration was achieved from one-week-old seedling shoot-tip explants via multiple-shoot-clumps and also somatic embryos. The multiple-shoot-clumps were produced on MS medium containing BA (0.5, 1.0 or 2.0 mg/$L^{-1}$), with biweekly subculture. Somatic embryos were directly produced on the enlarged dome shaped expansive structures that developed from shoot-tip explants (without any callus formation) when cultured on MS medium supplemented both with BA (0.5, 1.0 or 2.0 mg/$L^{-1}$) and 2,4-D (0.5 mg/$L^{-1}$). Whereas each multiple-shoot-clump was capable of regenerating more than 80 shoots via an intensive differentiation of both axillary and adventitious shoot buds, the somatic embryos were capable of 90% germination, plant conversion and regeneration. The regenerated shoots could be efficiently rooted on MS medium containing 1.0mg/$L^{-1}$ IBA and successfully transplanted to the glasshouse and grown to maturity with a survival rate of 92%. The plant regeneration efficiency of both the genotypes were similar. After the micro-projectile bombardment, expression of uidA gene was determined by scoring blue transformed cell sectors in the bombarded tissue by an in situ enzyme assay. The optimal conditions comprising a helium pressure of 2200 K Pa, the target distance of 11 cm with helium inlet fully opened and the use of osmoticum have been defined to aid our future strategies of genetic engineering in sorghum with genes for tolerance to biotic and abiotic stresses.

An efficient plant regeneration system in alfalfa (Medicago sativa L.) through somatic embryogenesis was established. Embryogenic callus was obtained by culture of hypocotyl segments on MS medium with 0.02mg $L^{-1}$ IAA and 1.0mg $L^{-1}$ zeatin after 45 days of culture. Embryogenic calli were converted to the somatic embryos when transferred to either MS medium without plant growth regulators (PGRs) or MS medium containing various cytokinin (BA, kinetin and zeatin). Most of the somatic embryos were developed into plantlets on MS medium supplemented with 0.1 mg $L^{-1}$ kinetin. Also, secondary embryos appeared on the surface of primary embryo but they showed abnormal growth. Regenerated plantlets were transplanted to pots containing vermiculite and perlite for further analysis.

The use of liquid-medium-based procedure relative to the solid media led to a 4.5-fold increase in the number of cotyledon-stage embryos. The most efficient system for multiplication and regeneration of somatic embryos was CP6 procedure with the media MSD40/MSD20/MSM6AC/FNL0S3S3GM. However, the rate of regeneration was lower. About 71％ of the embryos with dicotyledon were continued to develop the roots after desiccation treatment and 92％ of the germinated embryos produced shoots in 10 days. Of the four morphologically different types of embryos, dicotyledonous ones showed a high frequency of conversion, while only a few with fused and horn type cotyledon developed shoots. Mature somatic embryos were desiccated in empty petri dishes for 12-72 h. Embryo survival rate was the highest after 12 h of desiccation, but maximal germination was observed at 24 h. After desiccation, they were placed on MS medium without growth regulators for germination. Germinating embryos were transferred to small pots with vermiculite for plant regeneration. The etiolating the plants during the growth was resolved to add 1％ activated charcoal on hormone-free MS medium.

This study was carried out to establish The regeneration of healthy seedlings from the nodal segment culture of Chinese yam (Dioscorea opposita cv. Danma), cultivated in Korea. Different explants such as leaves, petioles, roots and nodal pieces, excised from the in vitro grown seedlings of Chinese yam, were cultured on MS medium supplemented with various combinations of growth regulators. All the growth regulators used induced plantlet regeneration from the nodal segments at a high frequency, while there was no induction of shoot or callus from leaf, petiole or root tissues. The medium supplemented with 0.01mg/L NAA, 0.5mg/L BA, 0.5-1.0mg/L kinetin and without plant growth regulator was effective for shoot development of buds from the nodal segment culture. The concentration of BA and NAA was an important factor in the bud induction of buds from the nodal segments of Chinese yam. Nodal segments cultured on the medium containing 1.0mg/L NAA and 0.5-1.0mg/L BA gave the best response to bud formation. The addition of GA$_3$ to the culture medium suppressed shoot induction and growth, while it increased microtuber formation. The shoot growth and microtuber formation were also affected by medium strength and solidity. The MS basal medium containing 1 g/L gelrite was suitable for microtuber formation from the nodal segment of Chinese yam.

Plantlet regeneration from the shoot apex was studied in three different genotypes of the chinese yam (Dioscorea opposita Thunb) cv. Jnagma and Danma, Dunggunma. The effects of plant growth regulators and inorganic salts concentration of the culture medium on bud induction and shoot growth were examined. The combinations of 0.2 mg/L BAP + 0.2mg/L kinetin, 0.01mg/L NAA + 0.2 mg/L kinetin and a single treatment of 0.2mg/L BAP were equally effective for bud and shoot formation from the shoot apices in the three cultivars. Auxin (2,4-D, NAA) treatment enhanced calli formation from the cultured apices. Also, the shoot apices of the cv. Dunggunma produced more callus and buds on the culture medium (MS) containing 0.05mg/L NAA and 0.5-1.0mg/L SAP. Lower salt strength of medium inhibited shoot elongation but did not have much effect on the shoot and bud induction from the shoot apices. These results will be useful to obtain disease-free plants of the Chinese yam.

To establish an efficient acclimation system for regenerated plantlets of soybean, we used various media with hydroponic nutrient solutions before regenerants were transplanted into soil. The hydroponic nutrient solution was essential for the survival of the plantlets. The vermiculite with nutrient solution at pH 5.5 was found to be the best medium with 97-100% survival rate and better growth of regenerants plantlets. Regeneraed grew best in the following order of solutions: Yoshida solution, modified Yoshida solution, SoyI, Soy II, and MS medium. However, Soy I solution (EC 2.9 mS/cm), developed by the Honam Agricultural Research Institute proved to be the most effective for acclimation in terms of the time required for vigorous growth and economical use of chemicals.

Somatic embryos were formed from calli obtained from axillary shoots (raised from nodal segments of glasshouse-grown plants under aseptic conditions), internodal segments (from in vitro-raised plants), and root and coty-ledonary leaf segments (from in vitro-raised seedlings) after 8 weeks of initial culture. Embryo formation was the highest (97.33%) from cotyledonary leaf callus on Mura-shige and Skoog's (MS) medium containing kinetin (KN) (3 mg/L). Somatic embryo induction was lesser with different combinations of auxins while it increased to 100% in internodal segment and cotyledonary leaf calli with 6-benzyladenine (BA) (2mg/L) along with 2,3,5-triiodobenzoic acid (TIBA) (2mg/L). The shoots were induced from somatic embryos raised from root, coty-ledonary leaf and internodal segment calli grown on MS medium containing BA in combination with indole-3-acetic acid (IAA). Maximum of 66.67% cultures formed shoots on MS medium containing BA (1mg/L) in combination with IAA (2mg/L). The shoots raised from somatic embryos were rooted on MS medium supplemented with indole-3-butyric acid (IBA) (2mg/L). The plantlets transferred to the field showed 70% survival rate after one year.

For long-term conservation of germ plasm, somatic embryos of sweet potato are important because shoot tips are not amenable to liquid nitrogen storage. Somatic embryos from different genotypes were used for induction of somatic embryogenesis in a large number of genotypes. Somatic embryogenesis was induced on 2,4-D medium in all the 11 genotypes, collected from geographically distinct locations. Genetic fidelity of the regenerated plants was confirmed by morphological and RAPD markers.

Callus and cell suspension cultures of Eurycoma longifolia Jack could be an alternative supply of 9-hydroxycanthin-6-one and 9-methoxycanthin-6-one. The callus tissues were initiated from leaves of different trees. The friable calli were used for the preparation of the cell suspension cultures of E. longifolia. The leaf explant of tree Eu-9 produced the most callus and also induced high cell biomass in the cell suspension culture, but it produced low quantity of 9-methoxycanthin- 6-one and 9-hydroxycanthin-6-one. The leaf explant from tree Eu-8 produced low quantity of callus and cell biomass, but produced the highest quantity of 9-methoxycanthin- 6-one and 9-hydroxycanthin-6-one. Optimum production of cell biomass was obtained on cell culture medium with pH 5.75 prior to autoclaving, but high alkaloids content could be induced in culture medium in acidic condition with pH 4.75 and 5.25 prior to autoclaving.