In vitro propagation of walnut - A review

<i>In vitro</i> propagation of walnut has played a very important role in rapid multiplication of cultivars with desirable traits and production of healthy and disease-free plants. During the last several years, different approaches have been made for in vitro propagation of walnut. Micropropagation using apicale bud, nodale segement, leaves, petioles, cotyledons, embryos and understanding the specific requirement at different stages has been comprehensively covered in literature. New challenges for refinements of protocols for high rate of shoot multiplication and development of cost effective methods has gained importance in the recent past. Importance of liquid and solid static culture for callus induction, embryogenesis, shoot proliferation and root induction for walnut is also discussed in the present review. Further, the development of protocols for in vitro propagation, culture nodal segment from seedling, somatic embryogenesis and plant regeneration which is considered the most important step for successful implementation of various biotechnological technique used for plant improvement programmes has been adequately addressed in literature. In walnut, there are severalreports which indicate rapid regeneration and multiplication through organogenesis or somatic embryogenesis. On the whole, the present review gives a consolidated account of in vitro propagation in walnut.Key words: Walnut, <i>Juglans</i> spp. L, root induction, shoot multiplication, regeneration, medium culture, micropropagation, somatic embryogenesis

The effects of BAP, IBA and genotypes on in vitro germination of immature walnut embryos

Abstract A prerequisite for most plant transformation systems is an efficient and reliable method to regenerate phenotypically normal plants. The present studies were undertaken with a view to the effects of Benzyl amino purine (BAP) and Indol butyric acid (IBA) hormones and genotypes on in vitro germination of immature embryos in walnut (Juglans regia L.). The immature embryos of walnut were excised from different cultivars and cultured on DKW basal medium supplemented with different plant growth regulators. Significant differences were observed among different cultivars and different concentration of BAP and IBA. The BAP and IBA induced the shoot, root and callus proliferation and embryo germination, but it was dependent on genotypes and hormones concentrations. The best performing medium for immature embryos germination was DKW basal medium supplemented with 1 mg L -1 alone and 1.5 mg L -1 BAP in conjunction with 0.01, 0.05 and 0.1 mg L -1 IBA (germination ratio vary between 49.32% and 67.76%). Percent germination of immature embryos was more when BAP and IBA were simultaneously applied as compared to those when applied separately