Principles of Plant Genetics and Breeding

(a) (b)
Figure 1 Examples of (a) Poa arachnifera and (b) P. secunda individuals.
Development of hybrids
BREEDING CROSS-POLLINATED SPECIES 323
A mature female P. arachnifera individual (2n = 56) collected near El Reno, Canadian County, Oklahoma, was pollinated by a
mature clone of P. secunda var. Sherman (2n = 63) (PI578850). Pollinations were achieved by placing the accessions adjacent
to each other and agitating the P. secunda pollen parent between 7.30 and 10.00 am and allowing the pollen to fertilize the
P. arachnifera females. One advantage in utilizing P. arachnifera in a Poa interspecific hybrid program relates to its dioecious
nature. Crosses are greatly simplified because the typical necessity for emasculation of pollen-setting structures is not a necessary
component of this type of hybridization scheme.
Seed heads were harvested about 25 days after pollination and were air dried for an additional 2 weeks. Due to the cobwebby
nature of the P. arachnifera seed heads, the inflorescences were broken by rubbing the seed heads between two hands. The seed
heads were sown in pots on top of a light potting soil mixture, then lightly covered with the same potting soil mixture. The pots
were watered, covered, and placed in a germination chamber. As seedlings emerged, they were transplanted to separate pots.
Seedlings were transplanted to the nursery and allowed to grow through the spring and winter. A vernalization period was
required to initiate flowering.
Pollen viability in the hybrids was estimated by examining the pollen grains obtained from freshly extruded anthers with a 40×
hand lens. Pollen grains exhibiting a pearly white phenotype were considered viable. Pollen grains exhibiting a golden-yellow,
crystalline phenotype were considered non-viable. Seed production was not estimated; however, the ability of individual plants
to generate viable seed was assessed by examining the florets and looking for the presence of seed. If plump seeds were observed,
additional seed heads from that individual were threshed by hand and any harvested seed was sown by the previously described
method.