Abstract
In this study the tomato cultivars Pearson Al-improved, Marmande and VFN-8 were grown at three planting dates, to identify the reproductive attributes and abnormalities implicated in the low yield of field-grown tomatoes, encountered in Qassim, Saudi Arabia, during the winter season. The planting dates started in September, 1987, with monthly intervals, and then repeated the following year. In all cvs, the number of flowers per plant decreased slightly, whereas fruit set percentage and average fruit weight decreased substantially, resulting in a significantly low yield, as planting date was delayed. The failure of fruit set and perhaps the reduction in average fruit weight could be ascribed to inefficient pollination during the first two plantings, in addition to lack of fertilization during the last planting. Inefficient pollination was due to poor pollen dehiscence and due to both poor pollen dehiscence and low pollen production during the first two and the last plantings, respectively, whereas the lack of fertilization was due to low pollen viability and female sterility. Cv Marmande outperformed the other cvs, followed by Pearson Al-improved, during late plantings.