Evolving techniques for in vitro somatic embryogenesis in polyembryonic mango varieties

Abstract

Studies were conducted for evolving techniques for in vitro somatic embryogenesis in polyembryonic mango varieties during 1994 - 1996 in the Plant Tissue Culture Laboratory of the Department of Horticulture, College of Agriculture, Vellayani. Attempts were made to standardise the various stages of somatic embryogenesis, namely, induction, initiation, maturation and germination using nucellus and embryo mass as explants. Among the SIX varieties attempted for induction of somatic embryogenesis from nucellus, Kalluvarikka recorded the highest percentage of response (85.0) and Vellari Manga the least (68.9). Induction of somatic embryogenesis from nucellus was found to occur at its maximum on MS medium having half strength major salts, supplemented with 2,4 - D 5.0 mg/l, GA3 5.0 mg/l, glutamine 400 mg/l, sucrose 60 g/l, coconut water 200 ml/l, agar 6.0 g/l and activated charcoal 2.5 g/l, in darkness. The highest callus index was recorded when 2,4 - D 5.0 mg/l was substituted with BA 16 mg/l in the same medium. Initation of .somatic embryo genesis from nucellus occurred at its best in darkness on MS medium having half strength major salts, supplemented with BA 1.0 mg/l, glutamine 400 mg/l, casein hydrolysate 500 mg/I, sucrose 60 g/l, coconut water 200 mIll agar 5.5 g/l and activated charcoal 2.5 g/l.

Maturation of nucellus derived somatic embryoids was found at its best on a combination of basal media with B-5 major salts and MS minor salts supplemented with ABA 3.0 mg/l, casein hydrolysate 100 mg/l, sucrose 40 g/l, PVP 10 g/l, coconut water 200 ml/l and agar 5.0 g/l, in darkness. Germination of somatic embryoids derived from nucellus occurred only in presence of light, on a combination of basal media with B-5 major salts, MS minor salts, supplemented with BA 0.1 mg/l, sucrose 50 g/l, PVP 10 g/1 and agar 5.0 g/l. Somatic embryos were produced directly from embryo mass explants in darkness on solid MS medium having half strength of major salts supplemented with 2,4 - D 5.0 mg/l, GA3 5.0 mg/l, glutamine 400 mg/l, sucrose 60 g/l, coconut water 200 ml/l, agar 6.0 g/I and activated charcoal 2.5 g/l. The embryoids having sufficient size resulted from this treatment were able to attain near normal germination in presence of light on medium having a combination of B - 5 major salts and MS minor salts, supplemented with BA 0.1 mg/l or 0.2 mg/l, sucrose 50 g/l, PVP 10 g/l and agar 5.0 g/1.