Despite the importance of okra, as one of the important vegetable crop, very little attention has been paid to its genetic improvement using advanced biotechnological tools. The exploitation of marker assisted breeding in okra is often limited due to the availability of a few molecular markers, the absence of molecular genetic-map(s) and other molecular tools. Chromosome linkage-groups were not yet constructed for this crop and reports on marker development are very scanty and mostly hovering around cultivar characterization. Besides, very little progress has been observed for transgenic development. However, high throughput biotechnological tools like chromosome engineering, RNA interference (RNAi), marker-assisted recurrent selection (MARS), genome-wide selection (GWS), targeted gene replacement, next generation sequencing (NGS) and nanobiotechnology can provide a rapid way for okra improvement. Further, the etiology of many deadly viral diseases like the yellow vein mosaic virus (YVMV) and okra enation leaf curl virus (OELCV) in okra is broadly indistinct and has been shown to be caused by various begomovirus species. These diseases cause systemic infections and have a very effective mode of transmission; thus, preventing their spread has been very complicated. Biotechnological interventions have the potential to enhance okra production even under different viral-stress conditions. In this background, this review deals with the biotechnological advancements in okra per se along with the begomoviruses infecting okra, and special emphasis has been laid on the exploitation of advanced genomic tools for the development of resistant varieties.

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Biotechnological Advancements and Begomovirus Management in Okra (Abelmoschus esculentus L.): Status and Perspectives.

Role of reduced nitrogen for induction of embryogenic callus induction and regeneration of plantlets in Abelmoschus esculentus L.

The present invention provides medium compositions and methods for the regeneration of the whole plant from explants obtained from plants belonging to the Malvaceae family, particularly the Abelmoschus genus, more preferably Abelmoschus esculentus L, through somatic embryogenesis. The present invention also provides an efficient methodology for genetic transformation of plants belonging to the Malvaceae family through somatic embryogenesis in semisolid culture with the use of the Agrobacterium . The present invention is also related to a method for the development of virus-resistant transgenic plants belonging to the Malvaceae family.

Regeneration and genetic transformation of okra through somatic embryogenesis

Regeneration of recalcitrant okra (Abelmoschus esculentus [L.] Moench) plants in vitro would permit their rapid propagation and also aid in genetic transformation. Explants (hypocotyls, cotyledonary nodal meristems, cotyledons and shoot tips) were excised from okra seedlings that were grown aseptically in Murashige and Skoog (MS) basal nutrient medium. The explants were cultured on MS medium supplemented with auxins, cytokinins, and different auxin-cytokinin combinations. More organogenic callus was obtained on medium fortified with MS nutrients with low concentrations of 2,4-D (dichlorophenoxy acetic acid), NAA (�-n aphthalene acetic acid) and TDZ (thidiazuron), in combination. Shoots were produced on hypocotyls, cotyledonary nodes, and shoot tips, and calli were derived from leaf and cotyledon explants cultured in medium supplemented with BAP (6-benzylaminopurine) and TDZ. Both Kn (kinetin) and Zn (zeatin) proved ineffective in inducing either shoot buds or shoots. Roots were induced on elongated shoots using MS medium containing NAA or IAA (indole-3-acetic acid). Genetic transformation was carried out with Agrobacterium tumefaciens carrying the plasmid pBI121 with a selectable marker gene for nptII (neomycin phosphotransferase). Transformed cells were cultured on kanamycin (50 mg/L) and cefatoxime (300 mg/L). Proliferation of callus was achieved, with complete suppression of Agrobacterium. About 50-60% calli showed GUS (�-glucuronidase) expression, confirming transformation. Thus, genetic transformation of okra was successfully achieved by optimizing various parameters for regeneration and Agrobacterium infection. The regenerated plants were successfully hardened in earthen pots after adequate acclimatization.

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VutukuriManorama Kanuri

Papers

In Vitro Plant Regeneration and Genetic Transformation of Okra (Abelmoscus esculentus (L.) Moench)