Breeding Tomatoes for All Seasons

Tomato genotypes have been field screened for fruit setting ability under high temperature (>30° day >21° night) and humidity conditions. Several genotypes have had good fruit set, but Cl l1d from the AVRDC in Taiwan is the most prominent heat tolerant source in current breeding lines. Fruit characters being selected are: large size, firmness, jointless stems, good shape, good color, even ripening, blossom-end smoothness, and no cracks. Disease resistance being incorporated include Fusarium wilt (F. oxysporum F. sp. lycopersici) races 1, 2 and 3, gray leaf spot (Stemphylium solani Weber), bacterial wilt (Pseudomonas solanacearum E. F. Smith), and bacterial spot (Xanthomonas campestris pv. vesicatoria). To further enhance fruit setting, a parthenocarpy gene (pat-2) has been incorporated into heat tolerant genotypes. In 1983, two such lines had yields equal to and greater than Cl l1d under high and low temperature conditions, respectively. This gene combination could result in horticulturally acceptable, multiple disease resistant breeding lines which will set fruit under both high and low temperatures and/or high humidity conditions not conducive to pollination.