CHROMOSOME AND PROTEIN DIFFERENTATION IN THE AGROPYRON SCABRIGLUME COMPLEX

Abstract

The genus Agropyron (Gramineae) is represented in South America by about 12 species, all of which are polyploid. Some of these polyploids seem to have originated through hybridization between tetraploid Agropyron species and diploid Hordeum (Hunziker 1955, 1966, 1967). Hexaploid Agropyron scabriglume, for instance, (2n = 42) seems to have originated through allopolyploidy between tetraploid Agropyron tilcarense (2n =28) and a diploid Hordeum species (2n 14) (Hunziker, 1966, 1967). In recent contributions the author discussed the possible origin of A. scabriglume and the diversity within it on the basis of morphological, cytogenetic, distributional and biochemical data. This taxon was found to consist of a series of geographically isolated populations most of which cannot be distinguished on morphological grounds. It has been already shown that these populations show striking differences in chromosome repatterning and in the quality of their seed proteins (Hunziker, 1966, 1967). In this brief report the author will present additional cytogenetic evidence on the parental populations and on two new hybrids. Furthermore, new information on the seed protein of most populations is presented. The structure of the whole A. scabriglume complex will be discussed on the basis of the new evidence. The cytological observations were made as previously described (Hunziker, 1966, 1967). The electrophoretic experiments were performed following the same procedure as described by Johnson and Hall (1965). Agropyron scabriglume is a perennial, self-compatible species which has a discontinuous area and is found in damp meadows or river banks from Northern to Southern Argentina. The distribution of this species covers a wide range of latitude as well as altitude. It extends from 3,500 meters above sea level at 22? South Lat. to 100 meters altitude near 38? South Lat. (Fig. 1). It has been found in the valleys of Humahuaca (Jujuy), Cachi (Salta), Tafi (Tucuman), the Precordillera and the Nevado of San Rafael in Mendoza, the mountains of San Luis, the Sierras of Balcarce, the General Acha Valley (La Pampa), the Andes of Neuquen and the Rio Negro Valley. It has not been found in the extensive plains that separate some of these mountain regions (Hunziker, 1967). In general, there are no morphological differences between these populations. There are only three that can be easily separated from the rest on morphological grounds. One is from San Martin (San Luis Prov.), which has pubescent upper surface of the leaf blade; the other two populations have geminate spikelets in almost or nearly almost all of the spike nodes. The latter have been found recently in El Carancho (La Pampa Prov.) and Balcarce (Buenos Aires Prov.) (Fig. 1). There are, however, ecological differences between most of these races which become evident when they are cultivated in a uniform environment. In the environmental conditions of Castelar, Buenos Aires Province, at sea level, with warm summers, the San Martin strain is the most precocious; the La Quiaca strain has