S
TAGE
OF
M
ICROSPORE
D
EVELOPMENT
The most critical factor affecting haploid production from anther and microspore culture is the
stage of microspore development; for many species, success is achieved only when anthers are
collected during the uninucleate stage of pollen development. In contrast, optimum response is
obtained in tobacco and
Brassica napus
L. from anthers cultured just before, during, and just after
the first pollen mitosis (late uninucleate to early binucleate microspores).
In developing a protocol for anther culture, one anther from each bud is usually set aside and
later cytologically observed to determine the stage of microspore development. In many cases,
anthers within a bud are sufficiently synchronized to allow this one anther to represent the remaining
cultured anthers. Measurements of physical characteristics of the flower, such as calyx and corolla
length and anther color, shape, and size, are also recorded. Results of the experiments are analyzed
to determine which microspore stage was the most responsive. The physical descriptions of the
buds and anthers are then examined to determine if this microspore stage correlates to any easily
identified inflorescence, flower or anther characteristic(s). For example, in tobacco, buds in which
the calyx and corolla are almost identical in length usually contain anthers having microspores at
or near the first pollen mitosis. A researcher wishing to produce a maximum number of haploid
plants of tobacco would collect only buds fitting this physical description.