Abstract
It was found that all the cultivars must have produced fertile pollen for all the 6 x 6 crosses produced at lent some viable seeds. Some cultivars were poorer than others when used as females but no cultivar was always poor. The significant growth correlation between the number of viable seeds per hip helps to confirm the view that hip growth is controlled by the fruits developing in the hip. The viability of seed (tested with 1% tetrazolium chloride solution) generally ranged between 40% and 60%.
INTRODUCTION
In the breeding of new eultivars of roses there are many factors which influence seed production. These include pollen behaviour prior to pollination, pollen germination and pollen tube growth, stylar and stigmatic compatibility, aneuploidyr polyploidy, aporaixisi gametic and zygotic lethals, abortion and de. hiscence of inam1ture hip. In addition, the temperature and relative hun2idi ty prevailing during pollen maturation, pollen storage and crossing can affect the success rate. Lata (1071) found that tetrapIoid oultivars are mainly self* incompatible and reported good. seed set in six intervarietal crosses although he indentified one variety, Grus3 an Coburg, which was highly female sterile The relative ease of hybridization of cultivars has been reported by Atkins (1975) who listed some cultivars as good males, some as good female and some as both good. males and females. A comprehensive review of rose breeding with a discu. seion of its genetical basis has been given by Pal (1963). The practice of breeders is not constant. The method of Kordes et al. (1971) was to identify a plant which was particularly useful as either a male or a female parent and to avoid making reciprocal crosses while Korder (1.977) when seeking for a special colour used a number of mother plants and made a few crossess over a wide range to see what would happen.
