Panicum shastense (gramineae), a sterile hybrid between P. Pacificum and P. Scribnerianum

Natural and synthetic hybrids are reported betweenPanicum, scribnerianum Nash and two other species,P. pacificum Hitchc. & Chase andP. occidentale Scribn. & Merr. The hybrids are morphologically intermediate between the parents, and those in whichP. pacificum is one parent strongly resemble the rareP. shastense Scribn. & Merr. All the parent plants studied cytologically had regular meiosis and a gametic number ofn = 9 chromosomes. The hybrids usually showed good pairing of chromosomes in meiosis, but irregularities such as univalents and lagging chromosomes were common. In the hybrids generally less than 7% of the pollen grains stained with cotton blue in lactophenol, and the plants set no seed, whereas the parent plants generally had over 90% pollen stainability and a high percentage of seed set. Pollen fromP. shastense, like that of the hybrids, was 3–4% stainable.Panicum shastense is believed to be based on a first generation sterile hybrid and the nameP. xshastense is proposed.