Photoperiod-sensitive male-sterile mutant in tomato and its potential use in hybrid seed production

The current practice of manual emasculation of tomato flowers for hybrid seed production is labour-intensive and contributes significantly to the high cost of seed. Here we report on a photoperiod-sensitive, single gene male-sterile mutant (7B-1) in tomato which is 100% male sterile in long days (LD, minimum of 12 h daylength) in summer field conditions, but produces many male-fertile flowers in short days (SD, 8 h). In LD, 7B-1 flowers contain stamens that are pale, short and in the anthers microspore mother cells are differentiated but meiosis does not occur, i.e. microspores and pollen grains are not formed. Unlike the wild type flowers, the style and stigma of 7B-1 flowers are well exposed and this allows for ready access for pollination without emasculation. In SD, mutant flowers possess normal-looking orange-yellow anthers that enclose the stigma and produce normal viable pollen, which when used for pollination of 7B-1 flowers yield good fruit- and seed-set. The 7B-1 seed in turn generate a 100% population of male-sterile plants all of which can be used as female parents for hybrid seed production. The female fertility is not affected in 7B-1 flowers in both LD and SD conditions. The 7B-1 mutant has been grown in various field locations including, Saskatoon, California, Florida and in Chile, and at all locations it has shown stable male sterility. The 7B-1 mutant is a simple, natural and cost-effective system that has a strong potential for use in commercial-scale production of tomato hybrid seed.