Pollen Selection for Stress Tolerance or the Advantage of Selecting Before Pollination

Abstract

A series of studies has indicated that 60 75% of the structural genes which are expressed in the sporophyte of both angiosperms and gymnosperms are expressed, and thus subject to selection, also in the pollen (see ottaviano and Mulcahy, in press, for review). The consequences of this overlap between sporophytic and gametophytic genomes were first indicated by Ter-Avanesian (1949, 1978), later by others (see ottaviano and Mulcahy, in press), and more recently by Winsor, et al. 1987). Although the first studies of pollen selection have been conducted with cultivated plants, because of the technical advantages that these provide, the efficacy of pollen selection is not limited to cultivars. In Aureolaria flava (Scrophulariaceae), seedlings from the highest level of pollen tube competition in natural populations exhibited significantly larger rosettes and were more likely to produce flowering stems in the first season than were seedlings produced with little or no pollen tube competition (Ramstetter and Mulcahy, in prep.) These studies indicate that, in natural populations and in cultivars, pollen competition can be used to select for increased vigor (see ottaviano, this volume) and for increased stress tolerance, the subject of this article.