Inheritance and Cytology of the “Denton Dwarf”, Avena byzantina C. Koch 1

T H E spontaneous occurrence of dwarfs in the progeny of oat crosses has often been noted. These dwarfs have been reported to be characterized by sterility, failure to head, “prolific appearance”, and unusual panicle variations ( 4 ) . Perhaps the most interesting type of panicle variation occurring among the dwarfs was that one first reported by Derick (2) . This dwarf was found in a field of ‘Victory’ oats by Herman Trelle. The panicles of this dwarf were very compact, the culms were heavier than normal, and the spikelets were lacking one glume. This dwarf has been referred to as the “Trelle Dwarf”, C.I. 3634. Derick found that this dwarf in crosses with normal oats gave a 1:2:1 F2 ratio of normals to intermlediates to dwarfs which indicated segregation for a single factor in which dominance was not involved. Derick later made cytological observations of meiosis of dwarf, intermediate, and normal segregates and found the chromosome number to be normal in all three forms ( 3 ) . He did note, however, the presence of a terminally attached bivalent in the dwarf form he concluded was not a part of the normal chromosomle complement. He further stated that the presence of the terminally attached bivalent indicated a deficiency or translocation of a chromosome arm. In 1938 Atkins and Dunkle (1) found a similar dwarf in thle F, generation of the cross ‘Nortex’ x ‘Victoria’. This dwarf has been referred to as the Denton Dwarf, C.I. 3635. Both dwarfs have a decumbent juvenile growth habit and are very susceptible to crown rust, Pucciizia cororzata Cda. var. avenae, Fraser and Led. Longley and Stanton ( 5 ) reported that chromosome numbers of both dwarfs were normal and meiosis only “slightly irregular”. The inheritance of the Denton Dwarf character and further cytological observations on this dwarf are reported in this paper.