Embryo Culture in Diploid Cotton (Gossypium Arboreum L.)

Protocol ensuring in vitro establishment, maturation, regeneration and multiple shoot induction from immature embryos of diploid cotton, G. arboreum L. has been developed. Factors such as effect of media compositions, embryo age, size and light intensity during incubation were investigated. Immature embryos of various ages were harvested from 10, 15, 20 and 22 days after fertilization (ranging from 0.5 to 5 mm in size) and cultured for 30 days under light, dark and diffused light on various media compositions containing MS salts, proline (560 mg/L), casein hydrolysate (500 mg/L), BAP (2mg/L), GA₃ (40 ppm), activated charcoal (0.2%) and omnatax (500 ppm). In general, 22 days old embryos showed better culture establishment, maturation and germination compared to 10 and 15 days old embryos. Rapid and vigorous shoot growth was obtained on MS medium supplemented with 500 mg/L casein hydrolysate, 560 mg/L proline, 2 mg/L BAP, 40 ppm GA₃ and 500 ppm omnatax. The number of shoots emerging from embryo ranged from 2–4. Root multiplication was carried out on half strength MS solid medium supplemented with 0.2% activated charcoal. The protocol can be used for embryo rescue in elite crosses and can be used for producing multiple shoots and has value for multiplication in breeding programme where a method for micropropagation is not available and ultimately bombardment of immature embryos can also be exploited for production of transgenic plants.