Comparative Study of the Ploidy Series Bromus sterilis, B. diandrus and B. rigidus (Poaceae) Based on Chromosome Numbers, Morphology and Isozymes

Abstract

Chromosome numbers, morphological characters and isozymes of seven enzymes were studied to assess relationships between species of the Bromus diandrus‐rigidus polyploid complex and the closely related species, B. sterilis. The four different cytotypes detected, 2n = 14, 28, 42 and 56, could be divided into two species: B. sterilis (2n = 14, 28) and B. diandrus (2n = 42, 56) by morphological features and isozymes. The shape of the scar of rachilla segments in the floret proved to be a suitable character for distinguishing the two species, but not the chromosomal races within species. The tetraploid shared homozygous isozyme phenotypes with diploid B. sterilis at all loci, except one, suggesting that it is autopolyploid. No diagnostic isozymes could be found to distinguish between hexa‐ and octoploid cytotypes in the B. diandrus‐rigidus complex.

Molecular Phylogenetics of Bromus (Poaceae: Pooideae) Based on Chloroplast and Nuclear DNA Sequence Data

“…Because of its large size, taxonomic complexity, and wide geographic range, no comprehensive worldwide treatment of all species in Bromus exists, but many floristic treatments and keys of Bromus have been published for various geographic regions in the New World (e.g., Shear 1900;Wagnon 1952;Mitchell 1967;Soderstrom and Beaman 1968;Pinto-Escobar 1981Matthei 1986;Allred 1993;Pavlick 1995;Gutiérrez and Pensiero 1998;Planchuelo and Peterson 2000) and the Old World (e.g., Veldkamp et al 1991;Forde and Edgar 1995;Chen and Kuoh 2000;Spalton 2002bSpalton , 2004. Genetic variation within and among many species has been studied using data from isozymes (Kahler et al 1981;Ainouche et al 1995Ainouche et al , 1999Oja 1998Oja , 1999Oja , 2002aOja , b, 2007Bartlett et al 2002), as well as an array of DNA-based molecular techniques, including RAPDs and AFLPs (Ferdinandez et al 2001;Massa et al 2001;Puecher et al 2001;Ferdinandez and Coulman 2002) and microsatellites (Green et al 2001;Ramakrishnan et al 2002). A physical map of the chloroplast genome has been constructed for one species, B. inermis (Pillay 1993).…”

“…The tetraploid species in sect. Bromus are believed to be allopolyploids (Stebbins 1981), and their putative intrasectional origins have been elucidated using serology (Smith 1972), allozymes (Ainouche et al 1995;Oja 1998), and DNA sequence data (Ainouche and Bayer 1997;Ainouche et al 1999). One group of tetraploid species, the B. pectinatus complex, is believed to be of hybrid origin between sects.…”

“…Isozyme data have indicated that the three diploid species of sect. Genea are putative donors of genomes in the origins of the polyploid species in the section (e.g., Oja 1998Oja , 2002b.…”

“…Past attempts to understand phylogenetic relationships in Bromus among species and infrageneric taxa have been based largely on data from morphology (e.g., Shear 1900;Wagnon 1952), karyology (including chromosome number, satellite type, chromosome size, and DNA quantities) and hybridization experiments (e.g., Stebbins and Togby 1944;Stebbins 1947Stebbins , 1956Stebbins , 1981Schulz-Schaeffer 1960;Wilton 1965;Armstrong 1975Armstrong , 1981Armstrong , 1983Kozuharov et al 1981;Naganowska 1993a, b), serology (Smith 1969(Smith , 1972, and allozymes (e.g., Oja 1998Oja , 2007Oja and Jaaska 1998).…”

Chromosomes of Bromus auleticus Trin. ex Nees (Poaceae)

“…Chromosome size may be very different among species (Armstrong, 1983;Schifino and Winge, 1983). Ploidy levels may vary within the same species, as in B. diandrus and B. sterilis (Oja and Laarmann, 2002). The chromosome complements consist mainly of chromosomes resembling each other in size and centromere position (Joachimiak et al, 2001).…”