Identification, distribution and population variability of great brome (Bromus diandrus Roth) and rigid brome (Bromus rigidus Roth)

Abstract

Seventeen populations of Bromus spp. were sampled from across southern Australia and accessions in the state herbaria of Western and South Australia were examined. Rigid brome (B. rigudus) differed from great brome (B. diandrus) in having shorter, sparser hairs on leaf laminae, more compact and erect panicles with shorter spikelet branches. In rigid brome, the abscission scars on the rachillae were elliptical and the lemma calluses were elongated (> 1 mm), while in great brome, these characters were circular and short (5 1 mm). Rigid brome was further differentiated into a long and short-awned biotype. Rigid brome was hexaploid, 2n = 42, and great brome an octoploid, 2n = 56. Rigid brome is widely distributed across southern Australia, often growing unrecognized in association with great brome. Rigid brome matured earlier than great brome, and there was high genetic variation (26-34% of total variation) in the time of maturity of both species. Seed production in rigid brome and great brome ranged from 1156 to 2908 and 661 to 3380 seeds per plant respectively. A short-awned ecotype of rigid brome from Geraldton, W.A., had 30% residual innate dormancy. This, together with the earlier maturity of ecotypes of rigid brome, may make it more difficult to control than a great brome when both species coexist in the field. Leaves of great brome were susceptible to rust (Puccinia bromoides Guyot), but associated ecotypes of rigid brome were rust free.

Long‐term effect of different tillage systems on the emergence and demography of Bromus diandrus in rainfed cereal fields

“…). These results contradict previous works in which the highest emergences and densities of B. diandrus were observed in NT compared with other soil tillage systems (Gill & Blacklow, ; Kon & Blacklow, ; Riba & Recasens, ; Kleemann & Gill, ). Higher infestation levels were found in tillage systems in which seeds are superficially buried in the soil (ChP and SS) than in MbP and NT.…”

“…Kon and Blacklow () noted that there is a high heritable variation within Australian populations of B. diandrus that would allow further adaptations to changing environments. Kleemann and Gill () also observed great differences in germination patterns between B. diandrus populations and noted a possible interaction between seed dormancy and crop management practices.…”

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

“…They are predominantly self-fertilizing annual grasses, widely distributed in Europe, Mediterranean countries and SW Asia (Smith, 1980 [31] , 1985 [32] ; Sales, 1993 [26] , 1994 [27] ). Bromus diandrus and B. rigidus have been reported as polyploids with different intraspecific ploidy levels: B. diandrus (2n = 28, 42, 56) B. rigi-dus (2n = 28, 42, 56, 70) (Devesa et al, 1990 a [2] ; Kon and Blacklow, 1988 [14] ; Sanchez Anta et al, 1986 [28] ). Bromus sterilis is a closely related diploid (2n = 14) species (Devesa et al, 1990 b [3] ; Sanchez Anta et al, 1988 [29] ; Kozuharov et al, 1981 [15] ) which was shown to be a putative genome donor for the B. diandrus±rigidus polyploid complex in our previous isozyme study (Oja and Jaaska, 1996 [22] ).…”

Preliminary Isozyme Evidence on the Hybrid Origin and Diploid Progenitors of Bromus pectinatus (Poaceae)

“…Genea, except the diploid B. fasciculatus C. Presl, are widely introduced in North and South America, Australia, and New Zealand (Mack 1981;Upadhyaya et al 1986). Some species, e.g., B. diandrus Roth, B. rigidus Roth, and B. tectorum L., have spread rapidly in new areas and become problematic weeds (Kon and Blacklow 1988;DiTomaso 2000;Novak and Mack 2001).…”