Some Consequences of Raspberry Pollen Dilution for Its Germination and for Fruit Development

Abstract

Summary Comparisons of pyrene set were made between raspberry flowers pollinated with undiluted pollen and others pollinated with pollen diluted with talc, or killed pollen. Pollen dilution reduced set but the reduction was not the same for all maternal parents. It also reduced the rate of fruit ripening, increased the proportion of pyrenes without seed content and reduced the tendency for abortive carpels to develop into small empty pyrenes. Observations of numbers of pollen grains germinating in the styles revealed differences attributable to the maternal parents, the pollen germinating poorest on the parent whose pyrene set was reduced most by pollen dilution. There were also maternal × paternal interaction effects on pollen germination. It is concluded that pollen germination was conditioned by growth substances provided partly by the grains themselves and partly by the styles of the seed parent, and that there were interactions between the two sources. Reduction in pollen concentration affected several aspects of early fruit development, but quantitative differences in the amount of pollen applied did not reduce the adverse effects of using diploid pollen. This suggests that such effects do not arise through direct action of the pollen on the maternal tissues.

Detection of genetic factors controlling pollen–style interaction in maize

“…The postshedding components of pollen competitive ability, pollen germination and tube growth, are very sensitive to, and dependent on, the environment (Brewbaker & Kwack, 1963;Jennings & Topham, 1971). Germination ability is controlled, even in compatible species, by a complex system of signalling, precluding hydrating and tube extrusion until grains have landed on a stigma (Dickinson, 1993).…”

Aberrant segregation of a gene in the raspberry and its association with effects on seed development

“…For the diallels, variations in pyrene set, seed structure and seedling emergence have already been described, together with the methods used for measuring them (Jennings, 1971 a, b, c;Jennings and Topham, 1971). The data from the diallels were analysed by fitting constants to quantitative data on the percentage of recessives obtained.…”

“…Three experiments to study the effects of pollen dilution, two of which have already been described (Jennings and Topham, 1971). Pollen was diluted to 50 per cent.…”

“…This would also explain why auxin influenced the maternal effects of AR1 and 511/12 on segregation, though the fact that it had opposite effects on these two seed parents also needs explaining. There is evidence that the endosperms ofARl and 511/12 differ in growth substance concentration, which must be optimal for good fruit development (Jennings, 1971 b), so the different responses may be a consequence of this, especially if gene S is in some way involved in determining this difference.…”

“…This results suggests that S pollen tubes derived from Burnetholm were more competitive in the style than s pollen tubes, which were consequently more successful when competition was reduced by pollen dilution. Pollen dilution had considerable effects on seed development in the 1968 crosses of this series (Jennings and Topham, 1971), but neither pollen dilution nor gene S affected the time of seedling emergence. Pollen dilution improved the total number of seeds emerging by 15 to 20 per cent, but the difference was not statistically significant.…”