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Pineapple plants transformed with the bar gene for bialaphos resistance were evaluated for transgene stability, gene expression and tolerance to glufosinate ammonium, the active ingredient of the herbicide Basta Ò X, under field conditions. Genetically modified plants of the cv. Phuket were micropropagated, rooted and established in a shade house before transfer to an experimental plot. Seven months after transfer to the field, plants were tolerant to 1600 ml/rai of the herbicide Basta Ò X (stock concentration 15% w/v glufosinate ammonium), this being twice the dose recommended for field application of the herbicide. Genetically modified plants remained green and healthy following spraying with the herbicide. In contrast, non-transformed pineapple plants of the same cv. became necrotic and died within 21 days of spraying with the herbicide at a reduced concentration of 800 ml/rai. Bar gene stability and expression in clonally-derived plants were assessed by PCR, RT-PCR and Southern analyses at 120, 210, 240, 270 and 380 days following transfer of the plants to the field. The bar gene was stable and expressed in transgenic plants throughout the duration of the trial. Fruit characteristics and yield were not affected by transgene introduction and expression. Transgenic plants tolerant to glufosinate ammonium should facilitate more effective weed control in pineapple plantations without damage to the crop.

Random amplified polymorphic DNA (RAPD) analysis was applied to eight commercial cultivars of pineapple, two intergroup hybrids and two wild species. Morphologically, pineapple is divided into the Cayenne, Queen, Spanish, Maipure and Abacaxi groups. Members of the first three groups have been analysed in this study. The cultivars ‘Tradsithong’, ‘Phuket’, ‘Sawee’ and ‘Tainan’, with spiny leaves, form the Queen group. In ‘Pattavia’, ‘Nanglae’ and ‘Petburi no. 2’ (Cayenne group), spines are confined to the leaf tips. ‘Intrachitdang’ is normally placed in the Spanish group, which is morphologically similar to the Queen group, but with inferior quality fruit. DNA amplification products were compared from 16 arbitrary 10‐mer primers from which a dendrogram was constructed. The results confirmed morphological classifications for seven of the eight commercial cultivars, with the Queen and Cayenne groups as separate clusters. However, the cv. ‘Intrachitdang’ was more closely related to the Cayenne group. Two hybrids from reciprocal Cayenne × Queen group crosses, were more closely allied to the Queen group. The two wild species were outside the groups. RAPD analysis can be exploited to investigate relationships within pineapple germplasm.

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