Rice is a staple food for more than 3 billion people in more than 100 countries of the world but ironically it is deficient in many bioavailable vitamins, minerals, essential amino- and fatty-acids and phytochemicals that prevent chronic diseases like type 2 diabetes, heart disease, cancers, and obesity. To enhance the nutritional and other quality aspects of rice, a better understanding of the regulation of the processes involved in the synthesis, uptake, transport, and metabolism of macro-(starch, seed storage protein and lipid) and micronutrients (vitamins, minerals and phytochemicals) is required. With the publication of high quality genomic sequence of rice, significant progress has been made in identification, isolation, and characterization of novel genes and their regulation for the nutritional and quality enhancement of rice. During the last decade, numerous efforts have been made to refine the nutritional and other quality traits either by using the traditional breeding with high through put technologies such as marker assisted selection and breeding, or by adopting the transgenic approach. A significant improvement in vitamins (A, folate, and E), mineral (iron), essential amino acid (lysine), and flavonoids levels has been achieved in the edible part of rice, i.e., endosperm (biofortification) to meet the daily dietary allowance. However, studies on bioavailability and allergenicity on biofortified rice are still required. Despite the numerous efforts, the commercialization of biofortified rice has not yet been achieved. The present review summarizes the progress and challenges of genetic engineering and/or metabolic engineering technologies to improve rice grain quality, and presents the future prospects in developing nutrient dense rice to save the everincreasing population, that depends solely on rice as the staple food, from widespread nutritional deficiencies.

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Transgenic plants of an Indian isolate of Lemna minor have been developed for the first time using Agrobacterium tumefaciens and hard nodular cell masses 'nodular calli' developed on the BAP -pretreated daughter frond explants in B 5 medium containing sucrose (1.0 %) with 2,4-D (5.0 μM) and 2-iP (50.0 μM) or 2,4-D (50.0 μM) and TDZ (5.0 μM) under light conditions. These calli were co-cultured with A. tumefaciens strain EHA105 harboring a binary vector that contained genes for β-glucuronidase with intron and neomycin phosphortransferase. Transformed cells selected on kanamycin selection medium were regenerated into fronds whose transgenic nature was confirmed by histochemical assay for GUS activity, PCR analysis and Southern hybridization. The frequency of transformation obtained was 3.8 % and a period of 11-13 weeks was required from initiation of cultures from explants to fully grown transgenic fronds. The pretreatment of daughter fronds with BAP, use of non-ionic surfactant, presence of acetosyringone in co-cultivation medium, co-culture duration of 3 d and 16 h photoperiod during culture were found crucial for callus induction, frond regeneration and transformation of L. minor. This transformation system can be used for the production of pharmaceutically important protein and in bioremediation.

Sesame (Sesamum indicum) is an important oil seed crop that has not yet been transformed genetically. We report herein for the first time successful recovery of fertile transgenic plants of sesame from cotyledon explants inoculated with Agrobacterium tumefaciens carrying a binary vector pCAMBIA2301 that contains a neomycin phosphotransferase gene (nptII) and a b-glucuronidase (GUS) gene (uidA) interrupted with an intron. Green shoots recovered from A. tumefaciens-infected explants on selection medium [Murashige and Skoog (MS) basal medium containing 25.0 lM benzyladenine (BA), 25.0 mg l -1 kanamycin and 400.0 mg l -1 cefotaxime] were rooted on MS basal medium containing 2.0 lM indole-3-butyric acid and 5.0 mg l -1 kanamycin. The rooted shoots were established in soil and grown to maturity to collect seeds. The presence, integration and expression of transgenes in putative T 0 plants were confirmed by polymerase chain reaction (PCR), Southern blot hybridization and GUS histochemical assay, respectively. GUS activity was detected in vegetative and reproductive parts of T 0 and T 1 plants. Presence of thiol compounds in coculture medium and kanamycin selection at shoot regeneration and at rooting stages were found to be critical for transformation. The transgenes were inherited in Mendelian fashion in T 1 progeny as detected by PCR. RT-PCR analysis of T 1 plants confirmed the presence of transcripts of uidA gene. The transformation frequency was 1.01%, and 22-24 weeks were required from seed to seed generation time. This protocol can be used to transfer new traits in sesame for quantitative and qualitative improvement.

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An efficient and simple procedure for inducing high frequency direct shoot organogenesis and somatic embryogenesis in lentil from cotyledonary node explants (without both the cotyledons) in response to TDZ alone is reported. TDZ at concentration lower than 2.0 μM induced shoot organogenesis whereas at higher concentration (2.5-15 μM) it caused a shift in regeneration from shoot organogenesis to somatic embryogenesis. The cotyledonary node and seedling cultures developed only shoots even at high concentrations of BAP and TDZ, respectively. TDZ at 0.5 and 5.0 μM was found to be optimal for inducing an average of 4-5 shoots per cotyledonary node in 93 % of the cultures and 55 somatic embryos in 68 % of the cultures, respectively. The somatic embryos were germinated when transferred to lower TDZ concentration (0.5-1.0 μM). The shoots were rooted on MS basal medium containing 2.5 μM IBA. The plantlets were obtained within 8 weeks from initiation of culture and were morphologically similar to seed-raised plants. The possible role of stress in thidiazuron induced somatic embryogenesis is discussed.

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An efficient, rapid and direct multiple shoot regeneration system amenable to Agrobacterium-mediated transformation from primary leaf with intact petiole of blackgram (Vigna mungo) is established for the first time. The effect of the explant type and its age, type and concentration of cytokinin and auxin either alone or in combination and genotype on multiple shoot regeneration efficiency and frequency was optimized. The primary leaf explants with petiole excised from 4-day-old seedlings directly developed multiple shoots (an average of 10 shoots/ explant) from the cut ends of the petiole in 95 % of the cultures on MSB (MS salts and B 5 vitamins) medium containing 1.0 μM 6-benzylaminopurine. Elongated (2-3 cm) shoots were rooted on MSB medium with 2.5 μM indole-butyric acid and resulted plantlets were hardened and established in soil, where they resumed growth and reached maturity with normal seed set. The regenerated plants were morphologically similar to seed-raised plants and required 8 weeks time from initiation of culture to establish them in soil. The regeneration competent cells present at the cut ends of petiole are fully exposed and are, thus, easily accessible to Agrobacterium, making this plant regeneration protocol amenable for the production of transgenic plants. The protocol was further successfully used to develop fertile transgenic plants of blackgram using Agrobacterium tumefaciens strain EHA 105 carrying a binary vector pCAMBIA2301 that contains a neomycin phosphotransferase gene (nptII) and a β-glucuronidase (GUS) gene (uidA) interrupted with an intron.The presence and integration of transgenes in putative T 0 plants were confirmed by polymerase chain reaction (PCR) and Southern blot hybridization, respectively. The transgenes were inherited in Mendelian fashion in T 1 progeny and a transformation frequency of 1.3 % was obtained. This protocol can be effectively used for transferring new traits in blackgram and other legumes for their quantitative and qualitative improvements.