Correction to: TDZ-induced direct shoot organogenesis and somatic embryogenesis on cotyledonary node explants of lentil (Lens culinaris Medik.).

[This corrects the article DOI: 10.1007/s12298-008-0033-z.].

Progress and challenges in improving the nutritional quality of rice (Oryza sativa L.).

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.

Development of an efficient in vitro plant regeneration system amenable to Agrobacterium- mediated transformation of a recalcitrant grain legume blackgram (Vigna mungo L. Hepper).

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 B5 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 ß-glucuronidase (GUS) gene (uidA) interrupted with an intron. The presence and integration of transgenes in putative T0 plants were confirmed by polymerase chain reaction (PCR) and Southern blot hybridization, respectively. The transgenes were inherited in Mendelian fashion in T1 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.

Increase in growth, productivity and nutritional status of wheat (Triticum aestivum L. cv. WH-711) and enrichment in soil fertility applied with organic matrix entrapped urea.

Field experiments were conducted during two consequent years in semi-arid, subtropical climate of Rohtak district situated in North-West Indian state Haryana to evaluate the effects of eco-friendly organic matrix entrapped urea (OMEU) on wheat (Triticum aestivum L. cv. WH-711). The OMEU prepared in granular form contained cow dung, rice bran (grain cover of Oryza sativa), neem (Azadirachta indica) leaves and clay soil (diameter of particles < 0.002 mm) in 1:1:1:1 ratios and saresh (plant gum of Acacia sp.) as binder entrapping half of the recommended dose of urea. A basal application of organic matrix entrapped urea showed increase in plant growth in terms of fresh and dry weights, root length, root number, leaf number, tillers, plant height earlet number, earlet length and productivity in terms of grain yield and straw yield over free form of urea (FU) and no fertilizer (NF) application. The OMEU increased total soluble proteins, organic N and free ammonium content in the leaves at 45 and 60 days. The nutritional status of wheat grains in OMEU applied plants was almost similar to that observed for FU applied plants. An increase in organic carbon and available phosphorus (P) was observed in OMEU applied plots on harvest whereas pH was slightly decreased over FU applied plots. The microbial population and activity in terms of fungal and bacterial colony count and activities soil dehydrogenase and alkaline phosphatase were significantly higher in OMEU applied plots as compared to the FU applied plots. Our data indicate that OMEU which are low cost, biodegradable and non-toxic can be used to replace the expensive chemical fertilizers for wheat cultivation in semi-arid, subtropical climate.

Plant regeneration from mature embryo of commercial Indian bread wheat (Triticum aestivum L.) cultivars.

A simple, efficient, reproducible and comparatively genotype-independent in vitro plant regeneration protocol was developed for ten commercial Indian bread wheat cultivars using mature embryos as the explants. Three different auxins and five different combinations of growth regulators in a modified Murashige and Skoog's basal medium were assessed for their effect on callus induction and plant regeneration, respectively, in a high yielding and widely grown cultivar, PBW-343. The optimized conditions were further evaluated with nine other commercial cultivars. A simple novel approach of physical isolation of regenerable calli from non regenerable structures during the early callus phase was used to improve plant regeneration. Callus induced on 2.0 mg(-1) 2,4-dichlorophenoxyacetic acid (2,4-D) showed a regeneration frequency of 86 % with 7.5 shoots per explants on hormone-free medium. A considerable improvement in the regeneration frequency (up to 97 %) and the average of shoots (19 shoots per explants) was obtained with a combination of thidiazuron (TDZ) and 2,4-D.

Assessment of heavy metal tolerance in native plant species from soils contaminated with electroplating effluent.

Heavy metals concentrations of (Cr, Zn, Fe, Cu and Ni) were determined in plants and soils contaminated with electroplating industrial effluent. The ranges of total soil Cr, Zn, Fe, Cu and Ni concentrations were found to be 1443-3240, 1376-3112, 683-2228, 263-374 and 234-335 mg kg⁻¹, respectively. Metal accumulation, along with hyperaccumulative characteristics of the screened plants was investigated. Present study highlighted that metal accumulation in different plants varied with species, tissues and metals. Only one plant (Amaranthus viridis) accumulated Fe concentrations over 1000 mg kg⁻¹. On the basis of TF, eight plant species for Zn and Fe, three plant species for Cu and two plant species for Ni, could be used in phytoextraction technology. Although BAF of all plant species was lesser than one, these species exhibited high metal adaptability and could be considered as potential hyperaccumulators. Phytoremediation potential of these plants can be used to remediate metal contaminated soils, though further investigation is still needed.

Genetic transformation of Indian isolate of Lemna minor mediated by Agrobacterium tumefaciens and recovery of transgenic plants.

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 B5 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 ß-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.

Tissue Culture- and Selection-Independent Agrobacterium tumefaciens-Mediated Transformation of a Recalcitrant Grain Legume, Cowpea (Vigna unguiculata L. Walp).

A simple and generally fast Agrobacterium-mediated transformation system with no tissue culture and selection steps has been developed for the first time in a recalcitrant food legume, cowpea. The approach involves wounding of 1-day-old germinated seeds with a needle or sonication either alone or in combination of vacuum infiltration with A. tumefaciens EH105 (pCAMBIA2301) carrying a ß-glucuronidase (GUS) gene (uidA) and a neomycin phosphotransferase (nptII) gene for stable transformation. Sonicated and vacuum infiltrated seedlings showed the highest transient GUS activity in 90% of the explants. The sprouted co-cultured seeds directly established in soil and without selection were allowed to develop into plants which on maturity produced T0 seeds. The presence of the alien genes, nptII and uidA in T0 plants and their integration into the genome of T1 plants were confirmed by polymerase chain reaction (PCR) and Southern blot analyses, respectively. The transgenes were inherited in the subsequent T2 generation in a Mendelian fashion and their expression was confirmed by semi-quantitative PCR. The transformation frequency of 1.90% was obtained with sonication followed by vacuum infiltration with Agrobacterium. This approach provides favorable circumstances for the rapid meristem transformation and likely makes translational research ease in an important recalcitrant food legume, cowpea.

TDZ-induced direct shoot organogenesis and somatic embryogenesis on cotyledonary node explants of lentil (Lens culinaris Medik.).

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.

Sesame (Sesamum indicum L.).

Sesame (Sesamum indicum L.) is an important oilseed crop grown in India, China, Korea, Russia, Turkey, Mexico, South America, and several countries of Africa. Sesame seeds are rich in oil, proteins, unsaturated fatty acids, vitamins, minerals, and folic acid. Nearly 70% of the world's sesame is processed into oil and meal, while the remainder is channeled to food and confectionery industries. Production of sesame is limited by several fungal diseases, water logging, salinity, and shattering of seed capsules during harvest. Introgression of useful genes from wild species into cultigens by conventional breeding has not been successful due to postfertilization barriers. The only alternative for the improvement of S. indicum is to transfer genes from other sources through genetic transformation techniques. Here, we describe a simple, fast, and reproducible method for the Agrobacterium-mediated genetic transformation of S. indicum which may be employed for the transfer of desirable traits into this economically important oilseed crop.