Genomic male sterility in lettuce, a baseline for the production of F-1 hybrids

Male sterile plants of lettuce (Lactuca sativa L.) cv. 'Lake Nyah' were produced using a genotype-independent transformation method employing Agrobacterium tumefaciens with a binary vector. The latter carried the neomycin phosphotransferase II gene controlled by the nopaline synthase promoter and terminator sequences, enabling transformed shoots to be selected on medium containing kanamycin sulphate. In addition, expression of a pathogenesis-related glucanase gene linked to a tapetum-specific promoter, caused the dissolution of the callose wall of developing microspores in transgenic plants. All transformed plants were male sterile. Plants regenerated from uninoculated, excised cotyledons of 'Lake Nyah' exhibited normal microspore development and were fertile. These results suggest that callose degradation may cause male sterility and provides the opportunity for producing F1 hybrid seed in lettuce.