Scoparia Populations Research Articles

Effect of osmotic potential and temperature on germination of kochia (Bassia scoparia) populations from the U.S. Great Plains

AbstractDevelopment of integrated weed management strategies requires knowledge of weed emergence timing and patterns, which are regulated primarily by water and thermal requirements for seed germination. Laboratory experiments were conducted in fall 2017 to fall 2018 to quantify the effect of osmotic potential and temperature on germination of 44 kochia [Bassia scoparia (L.) A.J. Scott] populations under controlled conditions. Bassia scoparia populations were collected in fall 2016 from northern (near Huntley, MT, and Powell, WY) and southern (near Lingle, WY, and Scottsbluff, NE) regions of the U.S. Great Plains. Ten osmotic potentials from 0 to −2.1 MPa and eight constant temperatures from 4 to 26 C were evaluated. Response of B. scoparia populations to osmotic potential did not differ between the northern and southern regions. At an osmotic potential of 0 MPa, all B. scoparia populations had greater than 98% germination, and the time to achieve 50% germination (t50) was less than 1 d. At −1.6 MPa, 25% of seeds of all B. scoparia populations germinated. Osmotic potentials of −0.85 and −1.9 MPa reduced B. scoparia germination by 10% and 90%, respectively. Regardless of temperature regime, all populations exhibited greater than 88% germination. The germination rate was highest at temperatures between 15 to 26 C and did not differ between populations from northern versus southern regions. At this temperature range, all populations had a t50 of less than 1 d. However, at 4 C, B. scoparia populations from the northern region had a higher germination rate (5 h) and cumulative germination (7%) than populations from the southern region. Overall, these results indicate a wide range of optimum temperatures and osmotic potential requirements for B. scoparia germination.

Diversity of Nut and Seedling Characteristics and Its Relationship to Habitat Climate in Some Almond Species

This study carried out to evaluate variations and relationships of nut size, seedling morphological attributes and habitat climatic parameters in of Prunus scoparia (Spach) C. K. Schneid populations in comparison to three other almond species. A total of 10 populations including seven populations of P. scoparia and three of other almond species including P. elaeagnifolia Spach., P. eburnea Spach., and P. dulcis Mill. were raised from seeds in greenhouse condition. Results showed noticeable variations in the studied seedlings characteristics within and among the populations. Among P. scoparia, Nourabad, Shiraz and Lordegan populations were superior to other populations in most of the measured traits. Useful correlations were observed between nut and seedling traits, among them, the highest correlation (r = 0.89) was between nut weight and leaf width. Altitude and annual precipitation correlated positively with some of the nut and seedling characteristics (ranging from r = 0.13 to r = 0.33). Based on principal components analysis (PCA), the first three components explained 76.2 % of the total variation of morphological characteristics. Using cluster analysis as well as a bi-plot of PCA, the genotypes classified into two main clusters of wild and domesticated populations. The main cluster of the wild populations divided into three sub-clusters based on their botanical categorization, whilst P. scoparia populations clustered based on geographic proximity and climate similarity. Results may have important implications for managing these genetic resources as well as their use in future breeding programs especially for the development of new rootstocks for almond and stone fruits.

Integration of molecular and geographical data analysis of Iranian Prunus scoparia populations in order to assess genetic diversity and conservation planning

Evaluation of spatial and non-spatial distribution is of great importance for protection of plant’s genetic resources. Prunus scoparia, a wild almond species, is an important economically and ecologically food resource plant in Iran with specific characteristics such as self-compatibility, resistant to drought and fungus, bitterness as well as small nuts. This wild species can provide an enlarged gene pool and may be considered as a valuable germplasm source for breeding the cultivated almond. In this study, the conservation planning and genetic variation of 158 Prunus scoparia accessions was investigated with the aid of 36 SSR markers to reveal genetic distinctness and structure. The molecular markers studied showed quite high level of genetic diversity on the basis of Na = 6.47, Ho = 0.603 and He = 0.737. The result of Neighbor net analysis was not in parallel with STRUCTURE data as classified samples into two and 12 main groups, respectively. On the other hand, the results of GENELAND analysis ensured the population classification and the genetic relatedness between populations from STRUCTURE analysis due to use of geographical data. All samples were grouped based on their geographical location. Moreover, utilization of GIS data accompanied by appropriate number of SSR markers could provide the possibility of prioritizing of distribution regions in natural and unnatural environments. The species distribution modeling would also help gain comprehensive information on conservation strategies of this wild almond species.

EPSPS Gene Copy Number and Whole-Plant Glyphosate Resistance Level in Kochia scoparia.

Glyphosate-resistant (GR) Kochia scoparia has evolved in dryland chemical fallow systems throughout North America and the mechanism of resistance involves 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) gene duplication. Agricultural fields in four states were surveyed for K. scoparia in 2013 and tested for glyphosate-resistance level and EPSPS gene copy number. Glyphosate resistance was confirmed in K. scoparia populations collected from sugarbeet fields in Colorado, Wyoming, and Nebraska, and Montana. Glyphosate resistance was also confirmed in K. scoparia accessions collected from wheat-fallow fields in Montana. All GR samples had increased EPSPS gene copy number, with median population values up to 11 from sugarbeet fields and up to 13 in Montana wheat-fallow fields. The results indicate that glyphosate susceptibility can be accurately diagnosed using EPSPS gene copy number.

Differences in Germination, Growth, and Fecundity Characteristics of Dicamba-Fluroxypyr-Resistant and Susceptible Kochia scoparia

The widespread occurrence of herbicide-resistant (HR) Kochia scoparia is an increasing concern for growers in the US Great Plains and Canada. K. scoparia populations resistant to dicamba have been reported in six US states. Populations cross-resistant to dicamba and fluroxypyr have been reported from wheat fields in Montana, USA. It is unclear whether resistance to the auxinic herbicides (dicamba and/or fluroxypyr), can alter the fitness traits of K. scoparia. The objectives of this research were to compare the germination dynamics in response to thermal environment, vegetative growth and fecundity characteristics, and the relative competitive ability of dicamba-fluroxypyr–susceptible (S) vs.–resistant (R) K. scoparia selected from within a single segregating population (collected from wheat-fallow field in MT). S and R selected lines were developed after three generations of recurrent group selection. Compared to the S selected line, the R selected line had lower cumulative germination at all constant temperatures except 25°C, and at all alternating temperatures except 30/35°C. Also, the R selected line had delayed germination relative to the S selected line. The R had lower plant height, plant width, primary branches, total leaf area, stem diameter, and shoot dry weight compared with the S plants in the absence of competition. The reduction in seed production per plant resulted in a 39% fitness cost. The 1000-seed weight of R (1.6 g) was also less than that of S (2.6 g). When grown in an intraspecific competition at different mixture proportions, replacement series indices for the growth parameters further indicated that the R was less competitive than the S. Evident from this research, the dicamba-fluroxypyr–resistant R selected line is less likely to persist in a field population in the absence of the auxinic herbicides.

Gene amplification of 5-enol-pyruvylshikimate-3-phosphate synthase in glyphosate-resistant Kochia scoparia.

Field-evolved resistance to the herbicide glyphosate is due to amplification of one of two EPSPS alleles, increasing transcription and protein with no splice variants or effects on other pathway genes. The widely used herbicide glyphosate inhibits the shikimate pathway enzyme 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS). Globally, the intensive use of glyphosate for weed control has selected for glyphosate resistance in 31 weed species. Populations of suspected glyphosate-resistant Kochia scoparia were collected from fields located in the US central Great Plains. Glyphosate dose response verified glyphosate resistance in nine populations. The mechanism of resistance to glyphosate was investigated using targeted sequencing, quantitative PCR, immunoblotting, and whole transcriptome de novo sequencing to characterize the sequence and expression of EPSPS. Sequence analysis showed no mutation of the EPSPS Pro106 codon in glyphosate-resistant K. scoparia, whereas EPSPS genomic copy number and transcript abundance were elevated three- to ten-fold in resistant individuals relative to susceptible individuals. Glyphosate-resistant individuals with increased relative EPSPS copy numbers had consistently lower shikimate accumulation in leaf disks treated with 100 μM glyphosate and EPSPS protein levels were higher in glyphosate-resistant individuals with increased gene copy number compared to glyphosate-susceptible individuals. RNA sequence analysis revealed seven nucleotide positions with two different expressed alleles in glyphosate-susceptible reads. However, one nucleotide at the seven positions was predominant in glyphosate-resistant sequences, suggesting that only one of two EPSPS alleles was amplified in glyphosate-resistant individuals. No alternatively spliced EPSPS transcripts were detected. Expression of five other genes in the chorismate pathway was unaffected in glyphosate-resistant individuals with increased EPSPS expression. These results indicate increased EPSPS expression is a mechanism for glyphosate resistance in these K. scoparia populations.

Tandem amplification of a chromosomal segment harboring 5-enolpyruvylshikimate-3-phosphate synthase locus confers glyphosate resistance in Kochia scoparia.

Recent rapid evolution and spread of resistance to the most extensively used herbicide, glyphosate, is a major threat to global crop production. Genetic mechanisms by which weeds evolve resistance to herbicides largely determine the level of resistance and the rate of evolution of resistance. In a previous study, we determined that glyphosate resistance in Kochia scoparia is due to the amplification of the 5-Enolpyruvylshikimate-3-Phosphate Synthase (EPSPS) gene, the enzyme target of glyphosate. Here, we investigated the genomic organization of the amplified EPSPS copies using fluorescence in situ hybridization (FISH) and extended DNA fiber (Fiber FISH) on K. scoparia chromosomes. In both glyphosate-resistant K. scoparia populations tested (GR1 and GR2), FISH results displayed a single and prominent hybridization site of the EPSPS gene localized on the distal end of one pair of homologous metaphase chromosomes compared with a faint hybridization site in glyphosate-susceptible samples (GS1 and GS2). Fiber FISH displayed 10 copies of the EPSPS gene (approximately 5 kb) arranged in tandem configuration approximately 40 to 70 kb apart, with one copy in an inverted orientation in GR2. In agreement with FISH results, segregation of EPSPS copies followed single-locus inheritance in GR1 population. This is the first report of tandem target gene amplification conferring field-evolved herbicide resistance in weed populations.

Genotyping-by-sequencing as a tool to infer phylogeny and ancestral hybridization: A case study in Carex (Cyperaceae)

Determining phylogenetic relationships among very closely related species has remained a challenge for evolutionary biologists due to interlocus phylogenetic discordance and the difficulty of obtaining variable markers. Here, we used a Genotyping-by-Sequencing (GBS) approach to sample a reduced representation genomic data set and infer the phylogeny of seven closely related species in the genus Carex (Cyperaceae). Past attempts to reconstruct phylogenetic relationships among these species produced conflicting and poorly-supported results. We inferred a robust phylogeny based on >3000 GBS loci and >1300 SNPs (with a minimum sequence depth within individuals of 10) using maximum likelihood and Bayesian inference. We also tested for historical introgression using the D-statistic test. We compared these analyses with partitioned RAD analysis, which is designed to identify suboptimal trees reflecting secondary phylogenetic signal that may be obscured by the dominant signal in the data. Phylogenetic analyses yielded fully resolved trees with high support. We found two main clades, one grouping Carex scoparia populations and C. waponahkikensis, and a second clade grouping C. longii, C. vexans, C. suberecta and C. albolutescens. We detected marginally significant signals of introgression between C. scoparia and C. suberecta or C. albolutescens, and we rejected a hybrid origin hypothesis for C. waponahkikensis. Our results demonstrate the power of NGS data sets for resolving some of the most difficult phylogenetic challenges where traditional phylogenetic markers have failed.

Population Structure and Genetic Diversity ofPrunus scopariain Iran

Over 30 Prunus species and taxa below the rank of species are known from Iran. These wild taxa provide an enlarged gene pool and may be considered a valuable germplasm source for breeding cultivated almonds. The present study is a genetic diversity analysis of six P. scoparia populations using six nuclear SSR markers. We also studied correlations between the population genetic differences, morphological differences and geographical distance. All six SSR primers produced amplification. The highest number of alleles occurred in the Fars and Lorestan populations, with 121 and 114 alleles, respectively. Some of the alleles were shared by all populations, while some others were specific to one population only. The observed heterozygosity ranged from 0.675 in the Tehran population to 0.900 in the Fars and Lorestan populations, while the expected heterozygosity ranged from 0.783 in the Tehran population to 0.948 in the Fars population. Bayesian model-based clustering showed a good separation of populations at K ...