Induced nucellar embryogenesis <i style="">in vitro</i> for clonal multiplication of <i style="">Mangifera indica </i>L. var. Ambalavi: A dwarfing rootstock

Abstract

Nucellar embryogenesis was induced in <i style="">Mangifera indica </i>L. var. Ambalavi, a monoembryonic dwarfing rootstock. Nucellar tissue of young fruits of 3 developmental stages and measuring about. 2.5, 4 and 5 cm in length, responded differently to the same treatments of agarified nutrient medium used for induction of embryogenesis. Whilst 0.25 mg l^-l BAP along with 1 mg l^-l NAA was effective to induce embryogenesis in nucellus of youngest fruits, 0.5 mg l^-1 2iP alone was sufficient for nucellus of older fruits. However, all the differentiated embryos proliferated in a single treatment comprising 0.15 mg l^-1each of BAP and 2iP and 0.5 mg l^-l IAA, albeit with a different basal medium. Size of cotyledonary nucellar embryos ranging between 1.5 to 2 cm in length was necessary for their further development, maturation, germination (visible plumule and developed root) and convertibility (plantlet formation). Embryos of desirable size required the liquid state of the medium supplemented with 0.01 mg l^-1 ABA, 0.1 mg l^-1 IAA and 100 mg l^-1 PEG (M. Wt. 400), while the nitrogen content was also low for their near-synchronized development, maturation, germination and convertibility. In the optimum treatment, most of the embryos showed apparently normal development, of which 78.4% matured and 40.2% germinated, while 35.6% embryos produced plantlets. Such a high percentage of convertibility of nucellar embryos has not been obtained earlier. The hardened <i style="">in vitro</i>-raised plantlets survived <i style="">ex vitro </i>when first transplanted to Soilrite followed by their transfer to the garden soil. Furthermore, adventitiously rooted nucellar plantlets gave better transplant success, i.e., about. 70% than those with their initial root system, where it was about. 50%. The former also survived longer than the latter, i.e., beyond 4 months.