Somatic embryo induction in long staple Egyptian cotton (Gossypium barbadense L.) Giza cultivars: Effect of glucose, KNO3, and KH2PO4

Egyptian cotton (Gossypium barbadense L.) cultivars are known worldwide for the extra-long and long staple high quality. The application of molecular and cellular genetic tools for Giza cultivars improvement is absent to date. The present study investigated the effect of different factors on the somatic embryo induction from 2 widely cultivated genotypes across Egypt, Giza 96 and Giza95 as a step towards full regeneration and transformation. We studied the effects of glucose concentration (1.5-7.5%), KNO₃ (1-2.5X), and KH₂PO₄ (1-2.5X), in combination with two auxin-based media: N1B2 (0.25 mg/l NAA and 0.5 mg/l BA) and N3D1B2 (1.0 mg/l NAA, 0.1 mg/l 2,4-D, and 0.5 mg/l BA) over a 10-week culture period on somatic embryo induction and development. Results showed a significant genotypic effect, with cultivar G95 outperforming G96 yielding a mean of 131 normal embryos per treatment compared to 37 in G96. All the response of both genotypes to the tested factors was growth stage dependent. Low glucose levels (1.5–3%) produced more normal embryos during early culture, while moderate levels (4.5%) enhanced late-stage proliferation. High nitrogen (2X KNO₃) supported early induction, whereas moderate levels (1–1.5X) maximized embryo numbers. Moderate phosphorus (1–2X KH₂PO₄) improved both induction and later stage embryo development. Across treatments, media containing 2,4-D promoted higher embryo formation during the first 4–6 weeks, but its removal was necessary for proliferation at later stages. The present research identified key factors to optimize somatic embryo induction that will lead to future efficient regeneration and transformation of Egyptian cotton cultivars and their introgression into ongoing breeding programs.