PG Thesis
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Item Optimising in vitro somatic embryogenesis in polyembryonic mango (Mangifera indica L.) varieties(Department of Horticulture, College of Agriculture, Vellayani, 1995) Bindu, C P; Rajmohan, KStudies were conducted to optimise the in vitro propagation techniques via somatic embryogenesis in polyembryonic mango varieties (Vellari, Kalluvarikka, Thalimanga, Kilichundan, Pulichi and Varikka) of Kerala, during 1993-1994 at the Department of Horticulture, College of Agriculture, Vellayani. Culture media and conditions could be standardised for the first two stages of somatic embryogenesis, namely induction and initiation. However, attempts for inducing normal maturation and germination of the embryoids were not so successfu I . Five out of the six varieties of mango (except Ki I ichundan) responded to the induct ion treatments for somatic embryogenesis. Kalluvarikka recorded the highest per cent cultures (87.50) initiating somatic embryoids from the nucellar tissue. Puliehi was observed to initiate the highest per cent eultures (91.66) initiating somatic embryoids from embryo mass cultured. Somatic embryoids were induced and initiated from nucellus as well as embryo mass. From the nucellus, the embryoids were produced directly, without any intervening callus. The embryo mass gave rise to emb r y og e n i c ca I I us, multiple embryos or zygotic embryos. The somatic embryoids from nucellar tissue were best induced when cultured in darkness on half strength Murashige and Skooge basal medium supplemented with 2,4-D 5.0 mg/l, GA3 5.0 mg/l, glutamine 400.0 mgll, sucrose 60.0 g/l, coconut water 200.0 mIll, agar 6.0 g/l and activated charcoal 2.5 g/l. Somatic embryoids from nucellar tissue were found to be initiated in 55.50 per cent cultures on half strength Murashige and Skoog basal medium supplemented with 2,4-D 5.0 mg/l, BA 0.05 mg/l, glutamine 400.0 mg/l, casein hydrolysate 500.0 mg/l, sucrose 60.0 g/l, coconut water 200.0 mill, agar 6.0 g/l and activated charcoal 2.5 g/l. Darkness was essential for the initiation. Ambient temperature and in the culture room temperature (26°C) were equally effective for the initiation. Abscisic acid was tried, among other treatments, for inducing proper maturation of the somatic embryoids initiated from nucellar tissue. The maximum size of the embryoids was observed on half strength Murashige and Skoog basal medium supplemented with ABA 16.0 uM, casein hydrolysate 100.0 mgll, sucrose 40.0 gll, coconut water 200.0 mIll, agar 6.0 g/l and activated charcoal 2.5 g/l. the embryoids was not influenced by light. Size of Attempts for inducing normal germination of the somatic embryoids from the maturation medium were made using treatments involving plant growth substances (BA, 2iP, GA 3 and NAA), factors known to impart osmotic stress (Polyethelene glycol and high concentrations of sucrose and a g a r) , sodium butyrate, known to influence histone deacetylation, and activated charcoal, capable of absorbing inhibitors. However, the treatments were not very useful in inducing normal germination of the embryoids.Item Somatic embryogenesis in cocoa (Theobroma cacao L.)(Department of Agricultural Botany, College of Horticulture, Vellanikkara, 1993) Jolly Antony; Achamma OommenInvestigation on somatic embryogenesis in cocoa (Theobroma cacao L.) were carried out at the college of Horticulture, Kerala Agricultural University, Vellanikkara during the period 1989-91, with the objective of studying the developmental potential of somatic embryos and its differentiation into plantlet by means of in vitro techniques. Stem and leaf segments, cotyledons and enbryonic axes of embryos collected from four typical genotypes of cocoa namely criollo, Amelonado, Amazon-forastero and Trinitario were used as explant. Cotyledons and embryonic axes of immature embryos (100 days pot anthesis) when incubated on MS basal semisolid medium supplemented with NAA 2 mg/1, thiamine 1 mg/1, casein hydrolysate 0.2 per cent (W/V) and coconut water 15 per cent (v/v) under dark for seven weeks resulted in high frequency and intensity of embryogenesis. Stem segements remined recalcitrant without embryoid regeneration, while leaf segments had a little potential. Auxins conditioned the culture for embryogenic competence while cytokinins had an inhibitory effect. The effect of NAA 2ppm was not replaceable by other auxins such as IAA, 2, 4-D. 2,4-D was a poor quantitative and qualitative stimulant of embryogenesis. Studies on auxincytokinin interaction revealed the counteracting effect of cytokinin on auxin. Fully mature embryoids germinated in hormone-free liquid medium consisting of half the salt concentration of MS and 5 per cent sucrose when incubated at 3000 lux (16 hours) for two weeks. De-cotyledonisation of embryoids and its rinsing with sterile distilled water and dessication, each for three minutes, enhanced the differentiation into plantlet. Shoot growth was stimulated by exogenous supply of NAA, GA3 and coconut water. In vitro rooting was promoted by reducing the salt concentration of MS medium to half strength and supplementing with IBA and activated charcoal. Germination and regeneration of embryoid into plantlet was dependent on its size. Sizes ranging from 0-4 mm were sub-optimal for germination and differentiation. Larger embroids (4-6 mm) had greater potential for differentiation. Quantitative and qualitative differnces were expressed by cocoa genotypes. Amelonado was found to be superior to Criollo and Amazon types for the induction of embryogenesis from cotyledons. Trinitario was the least efficient. Embryogenic potential of Amazon embryonic axes was superior to Criollo and Amelonado types. Trinitario embryonic axes remained recalcitrant. Plantlets were derived from embryoids within a time span of 13 weeks in Amelonado, Criollo and Amazon types.