Stigma receptivity and seed set in protogynous buffelgrass

Buffelgrass, Pennisetum ciliare (L.) Link syn = Cenchrus ciliaris L., is an important warm-season perennial forage grass that is widely grown througho ut the arid tropics. It has perfect florets, and emasculation is thought to be required to produce controlled hybrids. This is a tedious, difficult un dertaking because of the small floret size. The flowering behavior of buffe lgrass is such that the stigmas are exserted from the floret prior to anthe sis, which is referred to here as the protogynous interval. This investigat ion was conducted to determine the duration of the protogynous interval in 447 buffelgrass accessions and to ascertain stigma receptivity during the p rotogynous intervals. Protogynous intervals in a field nursery near College Station, TX, for all accessions ranged from 1 to 4 d. Six accessions with protogynous intervals ranging from 1 to 3 d were used to investigate stigma receptivity under both self- and cross-pollinated conditions in a greenhou se. Pollen germination and tube growth were observed with fluorescent micro scopy at different time increments following pollination. Across all access ions, pollen germinated within 15 min of contacting the stigma, and pollen tubes grew to the micropyle within 2 to 6 h, depending on the accession and pollen source. Mean seed set ranged from 11 to 76% and from 22 to 80% amon g accessions following self and cross-pollination, respectively. This inves tigation revealed that variation exists for protogynous interval within buf felgrass, and the stigmas are receptive when exserted from the floret and r emain receptive throughout duration of the protogynous interval regardless of whether it occurs 3, 2, or 1 d prior to anthesis. These findings demonst rate that protogyny can be used to produced controlled hybrids in sexual bu ffelgrass without emasculation.