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 several
reports 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.