Recovery of plantlets from apical meristem culture

--V. R. Bommineni, D. B. Walden and R. I. Greyson

The axillary bud procedure (Raman et al., Ann. Bot. 45:183-189, 1980) has recently been employed by us to propagate and maintain a single seedling sweet corn (cv. Seneca-60) genotype through 13 generations. Irish and Nelson (Planta 175:9-12, 1988) reported recently the recovery of plants through shoot tip culture from greenhouse grown plants. However, these two procedures, i.e. axillary bud culture and seedling shoot tip culture, appear to have limitations of genotype specificity; the number of recovered plants which are fertile is very low; and/or the meristems are incapable of surviving further manipulation.

In an attempt to circumvent these difficulties, and provide a suitable plant regeneration culture system, we have developed a medium to recover the plants from the shoot apical meristems (0.5-1.0mm long) from immature embryos or 72h imbibed seeds.

Plants were grown in the glasshouse and pollinations were made during the spring of 1988. Ears were harvested after 12-14 days of pollination and surface sterilized for 25-30 min with 10% 'Javex' after removing the husk leaves. Each embryo (1.0-2.5mm long) was removed from the caryopsis, the embryonic axis was separated from the scutellum and the coleoptile primordium was removed to expose the apical meristem. The final size of meristems ranged from 0.5-1.5mm. The excised meristems were placed onto a medium which consisted of Murashige and Skoog salts plus 500mg/l L- proline, 100mg/l casein hydrolysate, 30g/l sucrose, and 8% agar. Ten to fifteen explants were placed in a 150x25mm petri dish. The explants were incubated under white fluorescent lights for two weeks (Bommineni and Greyson, MNL 60:94-95, 1986).

In two weeks each explant developed as an individual plantlet with roots and leaves. The data are summarized in Table 1. The recovery of plantlets was high in all the geno-types cultured. The plantlets were transferred to small plastic pots with glasshouse soil mixture. After 2-4 weeks, the plants were transferred to large pots and grown to maturity. Pollinations were made on these plants, and fertile seeds were recovered.

Table 1. The number of plants recovered in MS medium from shoot apices cultured from immature embryos of different genotypes.
(a) (b) (c) (d) (e)
Genotype Shoot tips cultured  Plants potted  Plants producing inflor.  Percentage*
Oh43 63 62 62 98
M14  13 11 11 85
Oh43 x W23 30 30 30 100
W23 x M14 26 26 25 96
inflor. = inflorescences
*(e) = (b) / (d) x 100

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