Recovery of fertile plants from isolated, cultured maize shoot apices

Abstract

Maize shoot apices (1 to 2 mm size) from two sources were used to recover normal plantlets. The first explant source included shoot apices from the embryonic axis of immature embryos, 12-14 days post pollination in the glasshouse (spring) or 15-20 days post pollination in the summer nursery. In most explants, the shoot apical meristem was surrounded by a coleoptile primordium which was removed before culture. The second explant source included shoot apices from the plumules of 72 h imbibed mature kernels. The coleoptile and all other leaf layers (leaf-I to leaf-3 or 4) of the plumule were removed before culture to expose the apical meristem. Among the genotypes studied, a recovery of 43% (Mol7) to 100% (Oh43) of plantlets was achieved from shoot apices from immature embryo plumules cultured in MS medium. Recovery of 80% of Oh43 plantlets in MS medium and 40% of A188 plantlets from apices of plumules of imbibed (72 h) seeds in MS medium containing 2,4-dichlorophenoxyacetic acid was recorded. The plantlets derived from both explant sources grew normally and produced viable seeds upon pollination.

Agrobacterium tumefaciens-mediated expression ofgusA in maize tissues

“…However, because seedlings that originated from mature kernels were more variable in size and more likely to show fungal contamination, immature embryos were the preferred source of sterile seedlings. To ensure that all seedling materials were free of bacterial or fungal contaminants before explant isolation, sterilized immature embryos or mature seeds were germinated on sterile apex culture medium (Bommineni et al, 1989) in 25 X 100 mm Petri plates at 10 embryos or seeds per plate. This medium, which consisted of MS (Murashige and Skoog, 1962) salts and vitamins (pH 5.8) supplemented with sucrose (30 g 1-1), proline 500 mg 1-1, casein hydrolysate (100 mg 1-1), and 0.4% Bacto-Agar, encouraged rapid bacterial or fungal growth if these contaminants were present.…”