We investigated whether lines of transgenic tomato (Solanum lycopersicum) expressing the Bs2 resistance gene from pepper, a close relative of tomato, demonstrate improved resistance to bacterial spot disease caused by Xanthomonas species in replicated multi-year field trials under commercial type growing conditions. We report that the presence of the Bs2 gene in the highly susceptible VF 36 background reduced disease to extremely low levels, and VF 36-Bs2 plants displayed the lowest disease severity amongst all tomato varieties tested, including commercial and breeding lines with host resistance. Yields of marketable fruit from transgenic lines were typically 2.5 times that of the non-transformed parent line, but varied between 1.5 and 11.5 fold depending on weather conditions and disease pressure. Trials were conducted without application of any copper-based bactericides, presently in wide use despite negative impacts on the environment. This is the first demonstration of effective field resistance in a transgenic genotype based on a plant R gene and provides an opportunity for control of a devastating pathogen while eliminating ineffective copper pesticides.

/pdf/transgenic-resistance-confers-effective-field-level-control-1h1arb2o6u.pdf

Transgenic Resistance Confers Effective Field Level Control of Bacterial Spot Disease in Tomato

Plant defense against fungal pathogens by antagonistic fungi with Trichoderma in focus.

Antimicrobial peptides are a potent group of defense active molecules that have been utilized in developing resistance against a multitude of plant pathogens. Floral defensins constitute a group of cysteine-rich peptides showing potent growth inhibition of pathogenic filamentous fungi especially Fusarium oxysporum in vitro. Full length genes coding for two Petunia floral defensins, PhDef1 and PhDef2 having unique C- terminal 31 and 27 amino acid long predicted prodomains, were overexpressed in transgenic banana plants using embryogenic cells as explants for Agrobacterium–mediated genetic transformation. High level constitutive expression of these defensins in elite banana cv. Rasthali led to significant resistance against infection of Fusarium oxysporum f. sp. cubense as shown by in vitro and ex vivo bioassay studies. Transgenic banana lines expressing either of the two defensins were clearly less chlorotic and had significantly less infestation and discoloration in the vital corm region of the plant as compared to untransformed controls. Transgenic banana plants expressing high level of full-length PhDef1 and PhDef2 were phenotypically normal and no stunting was observed. In conclusion, our results suggest that high-level constitutive expression of floral defensins having distinctive prodomains is an efficient strategy for development of fungal resistance in economically important fruit crops like banana.

/pdf/petunia-floral-defensins-with-unique-prodomains-as-novel-aq7ibyuy38.pdf

Petunia floral defensins with unique prodomains as novel candidates for development of fusarium wilt resistance in transgenic banana plants.

Research continues to show that many artificial pigments are actually detrimental to our health. According to [1], there is an increasing consumer preference for healthy foods, which has invit‐ ed considerable demand for the use of anthocyanins as natural colorants, because of their natu‐ ral pedigree and healthful properties. Anthocyanins are the most widely distributed group of water-soluble plant pigments in nature. They are mainly responsible for the mauve, red, blue, and purple colors in flowers, fruits, leaves, seeds and other organs in most of the flowering plants. The other important class of water-soluble pigments are betalains, which are present on‐ ly in plants belonging to 13 families of Caryophyllales order [2-5]. An interesting phenomenon is the existence of mutual exclusiveness of anthocyanins and betalains in plant kingdom [3, 5-9]. Recent research demonstrated that simultaneous production of anthocyanins and betalains is possible in cell cultures and seedlings of anthocyanin producing plants by introduction and ex‐ pression of genes encoding dihydroxyphenylalanine (L-DOPA) dioxygenases in combination with substrate precursor feeding [10]. However, the co-occurrence of both pigments in the same plant species have never been found in nature and the plants which produce anthocyanins nev‐ er produce betalains and vice versa [6]. The commercial production of anthocyanin pigments is one of the fastest growing segments of the food colorant industry [2, 11]. The only industrial sources for anthocyanin pigments are from whole plant extracts [1], with the most common source being grape skins from the wine industry. According to [1], the demand of natural colo‐ rants continues to rise by 5-15% every year and this translated to the sales of anthocyanins isolat‐ ed from grape skins in 2002, which was estimated to be US$200 million worldwide. The increase

/pdf/production-of-anthocyanins-in-grape-cell-cultures-a-3875xwpgd7.pdf

Production of Anthocyanins in Grape Cell Cultures: A potential Source of Raw Material for Pharmaceutical, Food, and Cosmetic Industries

Transgenic banana (Musa acuminata ‘Gros Michel’) integrating either of two rice chitinase genes was generated and its resistance to Black Leaf Streak disease caused by the fungus Mycosphaerella fijiensis was tested using a leaf disk bioassay. PCR screening indicated the presence of the hpt selectable marker gene in more than 90 % of the lines tested, whereas more than three quarters of the lines contained the linked rice chitinase gene resulting in a co-transformation frequency of at least 71.4 %. Further, a unique stable integration of the transgenes in each line revealed some false negative PCR results and the expected co-transformation frequency of 100 %. The transgene insert number per line ranged from 1 to 5 and single transgene insert lines (25 % of all) were identified. Considerable delay in disease development (up to 63 days post-incoculation) over a monitoring period of 108 days occurred in nine lines with extracellularly targeted chitinase out of 17 transgenic lines tested and their necrotic leaf area decreased by 73–94 % compared to the untransformed susceptible control line. Finally, correlation between symptom development and rice chitinase expression was confirmed in two lines by Western analysis. The potential of rice chitinase genes to enhance resistance against M. fijiensis in banana was demonstrated as well as the usefulness of the leaf disk bioassay for early disease screening in transgenic banana lines.

/pdf/expression-of-a-rice-chitinase-gene-in-transgenic-banana-3nw5sh6xd8.pdf

Expression of a rice chitinase gene in transgenic banana (‘Gros Michel’, AAA genome group) confers resistance to black leaf streak disease

The most devastating disease currently threatening to destroy the banana industry worldwide is undoubtedly Sigatoka Leaf spot disease caused by Mycosphaerella fijiensis. In this study, we developed a transformation system for banana and expressed the endochitinase gene ThEn-42 from Trichoderma harzianum together with the grape stilbene synthase (StSy) gene in transgenic banana plants under the control of the 35S promoter and the inducible PR-10 promoter, respectively. The superoxide dismutase gene Cu,Zn-SOD from tomato, under control of the ubiquitin promoter, was added to this cassette to improve scavenging of free radicals generated during fungal attack. A 4-year field trial demonstrated several transgenic banana lines with improved tolerance to Sigatoka. As the genes conferring Sigatoka tolerance may have a wide range of anti-fungal activities we also inoculated the regenerated banana plants with Botrytis cinerea. The best transgenic lines exhibiting Sigatoka tolerance were also found to have tolerance to B. cinerea in laboratory assays.

Improved tolerance toward fungal diseases in transgenic Cavendish banana (Musa spp. AAA group) cv. Grand Nain

Suppression and overexpression of ubiquitin extension protein S27a affects cell proliferation and in vitro regeneration in Nicotiana benthamiana.

A system for genetic transformation and subsequent plant regeneration via indirect organogenesis from callus was developed for Aloe vera. Young seedlings served as primary explants. Callus cultures were established on Murashige and Skoog (1962) medium supplemented with 3 mg l−1 benzylaminopurine and 2 mg l−1 indole acetic acid. A protocol was developed to switch from the differentiated stage, using in vitro shoots or young regenerated plants, back to the de-differentiated stage of the callus and vice versa. Long-term maintenance of this callus paved the way for genetic manipulation of Aloe vera. Calluses were bombarded with a plasmid containing uidA and hpt genes, both under the control of the 35S promoter. Dithiothreitol and gibberellic acid were found to play a major role in reducing tissue necrosis following bombardment. Transformed shoots were regenerated under stepwise selection in hygromycin-containing liquid medium supplemented with different antioxidants. Amberlite XAD-4 resin was embedded into alginate beads and added to the selection medium. Amberlite was best for adsorbing different phenolic compounds and blocking explant necrosis. Shoot initiation occurred after transfer of the transformed cells to Murashige and Skoog medium supplemented with 2.0 mg l−1 thidiazuron and 0.1 mg l−1 indole butyric acid. Murashige and Skoog medium supplemented with 1 mg l−1 zeatin riboside promoted shoot elongation. Rooting and plant development were obtained on Murashige and Skoog basal medium supplemented with 15 mg l−1 hygromycin lacking growth regulators. The transgenic nature of the regenerated plants was verified by histochemical GUS assay and Southern blot hybridization.

https://www.jstor.org/stable/info/40981336

Aloe vera transformation: the role of Amberlite XAD-4 resin and antioxidants during selection and regeneration

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Improved tolerance toward fungal diseases in transgenic Cavendish banana (Musa spp. AAA group) cv. Grand Nain

Suppression and overexpression of ubiquitin extension protein S27a affects cell proliferation and in vitro regeneration in Nicotiana benthamiana.

Aloe vera transformation: the role of Amberlite XAD-4 resin and antioxidants during selection and regeneration