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Immature zygotic embryo cultures of neem yielded highly regenerative cultures, with the response varying with the embryo stage at culture. Early dicotyledonous stage embryos were the most responsive followed by torpedo stage embryos. The embryo cultures differentiated three types of regenerants: somatic embryos (SEs), shoot buds and neomorphs. SEs exhibited morphological abnormalities such as pluricotyledony, fusion of cotyledons and absence of cotyledons. Although these SEs showed secondary embryogenesis, the occurrence of normal dicotyledonous embryos was extremely rare. On MS basal medium 3% of SEs developed a long tap root but a plumular shoot did not appear. However, it was possible to regenerate plantlets from immature zygotic embryo cultures of neem via neomorph formation and adventitious shoot bud formation. The transplantation survival of these plants was more than 80%.

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Androgenic haploids of the neem tree (Azadirachta indica A. Juss.) were produced by anther culture at the early-to late-uninucleate stage of pollen. Haploid formation occurred via callusing. The best medium for inducing callusing in the anther cultures was Murashige and Skoog's basal medium (MS) (9% sucrose) supplemented with 1 µM 2,4-D, 1 µM NAA and 5 µM BAP, while anther callus multiplied best on MS medium supplemented with 1 µM 2,4-D and 10 µM Kn. These calli differentiated shoots when transferred to a medium containing BAP; 5 µM BAP was optimum for young calli (75% cultures differentiated shoots), but older calli showed the best regeneration with 7.5 µM BAP. Shoots elongated at a lower concentration of BAP -0.5 µM. These shoots were multiplied by forced axillary branching and rooted in vitro. The plants were subsequently established in soil. Of the plants that regenerated from anther callus 60% were haploid, 20% were diploid and 20% were aneuploid. Keywords Androgenesis · Azadirachta indica · Haploids · Medicinal plant · Woody plantAbbreviations BAP 6-Benzylaminopurine · CH Casein hydrolysate · 2,4-D 2,4-Dichlorophenoxyacetic acid · FAA Formalin acetic alcohol · IBA Indole-3-butyric acid · Kn Kinetin · NAA α-Naphthaleneacetic acid · TBA Tertiary-butyl-alcohol Materials and methods Plant material and initiation of aseptic culturesYoung inflorescences from a 50-year-old neem tree (Azadirachta indica A. Juss.) growing in the botanical garden of the University of Delhi were collected between 7.30 a.m. and 8.30 a.m. Two-millimeter-long flower buds with microspores at the early-to lateuninucleate stage were taken to the laminar air-flow cabinet, and further operations were carried out under aseptic conditions. These buds were surface sterilised with a 0.1% solution of HgCl 2 for 7 min, followed by three washings with sterile distilled water. The Communicated by W. Harwood