Genome Size Analysis of Weedy Amaranthus Species

Abstract

is the agricultural land of the Midwest. Given the intense farming practices used and the nearly constant changes Weedy Amaranthus species pose a serious threat to agriculture.in Best Management Practices, agrichemicals used, etc., One of the areas that causes the greatest concern is development of herbicide resistance and subsequent transfer of herbicide resistance the landscape is in a continual state of flux. If interspegenes among the species. To determine the potential impact of inter-cific hybridization does occur in Amaranthus, introgresspecific hybridization, one must first be able to detect such hybrids.sive hybridization could be very important in the evolu-To determine if genome size could be useful in the detection of intertion and adaptation of these weedy species. specific hybrids among the weedy Amaranthus species, the genome Murray (1940) reported that hybrids could be made sizes of the weedy Amaranthus species sympatric in Illinois were anaamong various monoecious and dioecious pigweed spelyzed. In a series of experiments, the genome sizes of these species cies. Wetzel et al. (1999) and Franssen et al. (2001) rewere determined by flow cytometric analysis. A significant variation ported the production of interspecific hybrids between was observed with respect to nuclear DNA content in the eight species two dioecious pigweed species. Tranel et al. (2002) reexamined. The genome sizes ranged from ≈0.95 pg in A. palmeri to ported interspecific hybridization between a monoe-≈1.4 pg in A. tuberculatus. Overlap of genome sizes among the species does exist; however, due to the reproductive biology of the species, cious and a dioecious pigweed species. In all the above this overlap does not preclude the detection of interspecific hybrids.reports, the hybrids were made under controlled, iso-Any dioecious weedy Amaranthus plant in Illinois that has a genome lated conditions. Trucco et al. (2005) demonstrated insize between 1.3 pg and 1.1 pg is probably a hybrid. Thus, the potential terspecific hybrids between A. hybridus and A. tubercufor genome size determination to reveal interspecific hybrids among latus under field conditions. Thus, it is possible that weedy Amaranthus species has been demonstrated. hybrids between pigweeds could occur naturally in agronomic fields. size to be 5.35 pg per 2C nucleus. Given the almost iden-MH 262 MH 262 Maricopa, AZ tical estimates of DNA, all the weed populations were con-MH 277 MH 277 Beckham, OK MH 254 Brazos, TX verted using 5.35 pg per 2C nucleus for W22 to maintain A. albus PT 66 PT 66 Champaign Co., IL consistency with other data published using W22 as an PT 106 PT 106 Morgan Co., IL internal standard. MH 40 MH 40 Dona Ana, NM MH 49 MH 49 Stoneville, MS The genome size of the pigweed species ranged from MH 55 MH 55 Centre Co., PA 0.96 to 1.21 pg per 2C nucleus in experiment 1 and 0.95 to A. blitoides MH 215 MH 215 Whitman Co., WA 1.23 pg per 2C nucleus in experiment 2 (Table 2). In MH 219 Franklin Co., MD MH 206 Harrow, Ontario both experiments, species were signif...

Nonhybrid Progeny from Crosses of Dioecious Amaranths: Implications for Gene-Flow Research

“…Grant (1959a) reported that Palmer amaranth chromosomes are small (2 to 3 lm) and not well differentiated. Consistent with this, Rayburn et al (2005) reported the genome size of Palmer amaranth to be smaller than most of the weedy amaranths with 2C ¼ approximately 0.95 pg. Grant (1959a) gave a chromosome count for the species of 2n ¼ 34.…”

Characterisation of the Amaranth Genetic Resources in the Czech Gene Bank

“…A major contributor to the noxious nature of these weedy species is their ability to efficiently adapt to the changes in agricultural management practices that are specifically designed to control and prevent colonization. For example, numerous populations of pigweeds have evolved herbicide resistance (Drzewiecki, 2001;Rayburn et al, 2005).…”

Gene amplification confers glyphosate resistance in Amaranthus palmeri

“…The first reported glyphosateresistant A. palmeri population was 6-to 8-fold more resistant than a susceptible population (3), and the glyphosate resistance mechanism in this population was previously unknown but is not due to differences in absorption or translocation of glyphosate (3). The mechanism is also not due to a ploidy change (3), because glyphosateresistant individuals had the reported A. palmeri genome size (22). Here, we use genetic and molecular analyses of EPSPS genes and proteins from glyphosate-resistant and -susceptible A. palmeri populations and demonstrate that amplification of the EPSPS gene is the glyphosate resistance mechanism.…”