Pollen selection.

In recent years a large number of reports have been published hinting about the possible role of selection at the male gametophyte level in natural conditions and its possible use as a tool in plant breeding programs. In this work, the evidence that has so far emerged on gametophytic selection is reviewed, and its relationship to pollen competition under natural conditions is analyzed. Information supporting an overlap in the genetic expression between the gametophytic and sporophytic phases is also reported, mainly in terms of isozymes and RNA hybridization. The correspondence between both phases is reviewed through their common response to different external agents such as temperature, salinity, metals, herbicides, fungal toxins, and other factors. Finally, the implications that pollen selection may have in plant breeding are evaluated.