Selections on the Empirical and Theoretical Investigations of Behavioral Variability: An Introduction to the Special Issue

The study of behavioral variability continues to grow in importance and gather interest. A thorough understanding of the fundamental processes by which variation is generated and by which it is adaptive is potentially important to our understandings of a whole host of phenomena, including all types of learning, from basic skills to language and thought (Bateson & Martin, 2013) as well as the antifragility of complex systems (Taleb, 2012). This issue represents a brief look into an important scientific enterprise, extraordinarily vast in scope and implications (Brembs, 2010). Even if we accept a fundamental unpredictability to animal behavior, this does not preclude us from studying the nature of that unpredictability. Please enjoy the issue, and may it inspire your own creative variations

Palmer Amaranth Populations from Kansas with Multiple Resistance to Glyphosate, Chlorsulfuron, Mesotrione, and Atrazine

Multiple herbicide-resistant (MHR) Palmer amaranth poses a serious management concern for growers across the United States. Since 2014, several Palmer amaranth populations with suspected resistance to most commonly used herbicides were collected in random field surveys across Kansas. This study aimed to characterize the resistance levels to glyphosate (EPSPS inhibitor), mesotrione (HPPD inhibitor), chlorsulfuron (ALS inhibitor), and atrazine (PS II inhibitor) in three suspected MHR Palmer amaranth populations (KW2, PR8, and BT12) compared to a known herbicide-susceptible (SUS) population. Dose-response studies revealed that PR8 and BT12 populations had 7- to 14-fold level resistance to glyphosate, and up to 12-fold level of resistance to chlorsulfuron (Glean herbicide) on the basis of visible control (LD50 values) and shoot dry weight response (GR50 values). The KW2, PR8, and BT12 populations also showed 2- to 4-fold resistance to mesotrione (Callisto herbicide) relative to SUS population. Based on plant dry weight response (GR50 values), the KW2 and BT12 populations showed 5- and 16-fold resistance to atrazine (AAtrex XP), respectively, compared with the SUS population. These results confirm the first report on the evolution of a Palmer amaranth population (BT12) with multiple resistance to glyphosate (12 to 14 fold), chlorsulfuron (11 fold), mesotrione (2 to 4 fold), and atrazine (16 fold) in Kansas. Further studies are in progress to investigate the response of these MHR populations to fomesafen (PPO inhibitor); 2,4-D; and dicamba (synthetic auxins) herbicides

Vida Alone and in Tank Mixtures for Spring Kochia Control in Fallow

No herbicide treatment provided more than 50% kochia control at Garden City, KS, or 80% kochia control at Hays after the first week of application. At Garden City, KS, treatments of Vida (pyraflufen) plus glyphosate and 2,4-D or dicamba, glyphosate alone, or glyphosate plus 2,4-D or dicamba provided greater than 89% kochia control. At Hays, glyphosate alone or with 2,4-D, and Vida plus dicamba alone or with glyphosate had greater than 85% control of kochia

Herbicide Strategies for Managing Glyphosate- and Dicamba-Resistant Kochia in Roundup Ready 2 Xtend Soybean

Kochia populations with multiple resistance to glyphosate and dicamba are an increasing concern for growers in the High Plains region, including Kansas. A field study was conducted at the Kansas State University Agricultural Research Center near Hays, KS, to evaluate and develop herbicide options for controlling glyphosate- and dicamba-resistant kochia in Roundup Ready 2 Xtend soybean. The study site was uniformly infested with a glyphosate- and dicamba-resistant kochia population prior to soybean planting. Fifteen herbicide treatments (programs), including PRE alone and PRE followed by (fb) POST-applied herbicides, were investigated in a randomized complete block design with four replications. All PRE treatments included Roundup PowerMax for control of other weed species. Results indicated that a single PRE application of Spartan alone or with Engenia, Panther PRO, and Zidua plus Valor SX provided season-long control of glyphosate- and dicamba-resistant kochia. A single PRE application of Engenia or Zidua alone only provided 70 to 78% kochia control at 6 weeks after POST (WAPOST) application. However, PRE-applied Zidua alone or with Engenia, Engenia alone, Spartan + Zidua, and Spartan + Sencor followed by a sequential POST application of a tank-mixture containing Engenia and Roundup PowerMax provided ≥ 95% kochia control at 6 WAPOST. Kochia biomass reduc­tion was \u3e 92% with a majority of the treatments; exceptions were Zidua PRE alone (59% reduction), Engenia alone (76% reduction), and Zidua + Engenia (88% reduc­tion) treatments. Soybean grain yield for a majority of the tested treatments did not differ, and ranged from 23 to 25 bu/a. These results suggest that effective PRE herbi­cide options are available for managing glyphosate- and dicamba-resistant kochia in Roundup Ready 2 Xtend soybean

Response of Dicamba/Fluroxypyr/Glyphosate-Resistant Kochia to Atrazine and Alternative Postemergence Herbicides

Two kochia accessions (KS-4A and KS-4H) were previously identified from a corn field near Garden City, KS, with multiple resistance to glyphosate (Roundup PowerMax), dicamba (Clarity), and fluroxypyr (Starane Ultra). The objectives of this research were to (1) determine the response of these kochia accessions to preemer­gence (PRE) and postemergence (POST) applied atrazine (Aatrex) in dose-response assays, and (2) determine the effectiveness of alternative POST herbicides. Seeds of a known susceptible kochia accession (SUS) collected from research fields in Hays, KS, were used for comparison. Greenhouse experiments were conducted at the Kansas State University Agricultural Research Center near Hays, KS, in a random­ized complete block design with 4 to 12 replications. For Aatrex PRE dose-response assay, germination trays (each 10- × 10-inch) containing field soil were used. Fifty seeds from each accession were separately sown on the soil surface in each tray. PRE applied Aatrex doses, including 0, 1/4X, 1/2X, 1X, 2X, and 4X (1X of Aatrex = 32 oz/a) were tested. Emerged kochia seedlings from each tray were counted 28 days after treatment (DAT). For Aatrex POST dose-response assay, kochia plants from SUS and KS-4H accessions were grown in 4- × 4-inch pots containing commercial potting mixture. The same doses of Aatrex (as for PRE dose-response) were tested on 3- to 4-inch tall kochia plants. In a separate greenhouse study, the SUS and KS-4H accessions were also tested with alternative POST herbicides. Data on percent visual control and shoot biomass were collected at 21 DAT in both Aatrex POST and alternative POST herbicide studies. Results indicated that the effective dose (ED50 values) of PRE applied Aatrex required for 50% reduction in seedling emergence of KS-4A, KS-4H, and SUS was 129, 7, and 1 oz/a, respectively, indicating 129- and 7- fold resistance in KS-4A and KS-4H accessions. Furthermore, the KS-4H acces­sion showed 248-fold resistance to POST applied Aatrex, as compared to SUS acces­sion. Among alternative POST herbicide programs, Gramoxone, Huskie, Talinor, and Sharpen alone or with 2,4-D provided excellent control (96-100%) of SUS and KS-4H accession at 21 DAT. In conclusion, these results indicate that dicamba/ fluroxypyr/glyphosate-resistant kochia from Garden City, KS, are also highly resis­tant to PRE and POST applied atrazine. However, alternative POST herbicides such as Huskie, Talinor, Gramoxone, Sharpen alone, or with 2,4-D were effective control options for this multiple resistant kochia accessions

Variable Response of Kochia Accessions to Dicamba and Fluroxypyr in Western Kansas

The rapid development of glyphosate resistance in kochia has increased the use of auxinic herbicides (dicamba and fluroxypyr) in the US Great Plains, including Kansas. Increasing reliance on auxinic herbicides for controlling glyphosate-resistant (GR) kochia may also enhance the evolution of resistance to these herbicide chemistries. The main objectives of this research were to (1) investigate the variation in kochia response to dicamba and fluroxypyr, and (2) characterize the dicamba resistance levels among progeny of kochia accessions collected from western Kansas. Greenhouse experiments were conducted at the Kansas State University Agricultural Research Center near Hays, KS. Discriminate-dose studies with field-use rates of Clarity (dicamba) (16 fl oz/a) and Starane Ultra (fluroxypyr) (0.6 pt/a) indicated that progeny from individual kochia plants (accessions) collected near Garden City, KS, had 78 to 100% and 85 to 100% survivors when treated with dicamba and fluroxypyr herbicides, respectively, at 28 days after treatment (DAT). In separate dicamba dose-response experiments, two putative dicamba-resistant (DR) kochia accessions viz., DR-110 and DR-113 collected near Hays, KS, had about 5- and 3-fold resistance to dicamba, respectively, based on fresh weight reduction (I50) compared to a dicamba-susceptible (DS) accession. Based on plant dry weight response, the DR-110 and DR-113 accessions showed 9- and 6-fold resistance to dicamba, respectively. These results confirm the co-evolution of cross-resistance to dicamba and fluroxypyr in kochia accessions from Garden City, and moderate to high level resistance to dicamba in the Hays accessions. Growers should adopt stewardship programs for auxinic herbicides and utilize all available weed control tactics to prevent further evolution of auxinic resistance in kochia populations

Auxinic Herbicide Mixtures for Controlling Multiple Herbicide-Resistant Kochia in Fallow

Kochia resistant to glyphosate (Roundup), chlorsulfuron (Glean), and dicamba (Banvel or Clarity) has become quite common in the U.S. Great Plains, whereas multiple resistance to additional herbicides, including fluroxypyr (Starane Ultra), atrazine (AAtrex), and metribuzin (Sencor) has also been reported recently. Effective management of these multiple herbicide-resistant (MHR) kochia populations warrants the need of alternative herbicide strategies. The main objective of this research was to investigate the efficacy of auxinic herbicides, including Duplosan (dichlorprop-p), Weedone (2,4-D), Clash (dicamba), and/or Pixxaro (premix of halauxifen and fluroxypyr) alone or in various combinations for controlling MHR kochia. Separate greenhouse and field experiments were conducted at the Kansas State University Agricultural Research Center (KSU-ARC) in Hays, KS. Greenhouse studies included an MHR kochia population (resistant to glyphosate, dicamba, fluroxypyr, chlorsulfuron, atrazine, and metribuzin) from Garden City, KS, and a susceptible (SUS) kochia population from Hays, KS. The postemergence (POST) applied herbicide programs, including Clash Weedone, Duplosan alone or in tank-mix combinations were tested. Field experiments were conducted in a fallow field at KSU-ARC with a natural infestation of kochia population with multiple resistance to glyphosate and dicamba. Herbicides, including Duplosan, Weedone, Clash, and Pixxaro were tested alone or in tank-mix combinations. Results from greenhouse study indicated that Clash, Duplosan, and Weedone applied alone provided inadequate control (5 to 42%) of MHR kochia at 21 days after treatment (DAT). In contrast, control of SUS population was 83 to 92% with Clash and Duplosan alone treatments. Tank-mixing Duplosan with Clash and/or Clash + Weedone significantly improved visible control (72 to 90%) of MHR kochia as compared to Duplosan, Clash, or Weedone alone treatments. Similarly, tank-mixing Clash to Duplosan or Pixxaro (two-way mixtures) and to Duplosan + Weedone, Pixxaro + Duplosan or Pixxaro + Weedone (three-way mixtures), provided an excellent control (91 to 97%) of MHR kochia compared to Clash, Pixxaro, Weedone, and Duplosan alone treatments in a field study. Altogether, these results suggest that tankmixing Clash with Duplosan and/or Pixxaro can potentially provide synergistic effect in controlling MHR kochia in fallow fields

Genomic-based epidemiology reveals independent origins and gene flow of glyphosate resistance in Bassia scoparia populations across North America

Genomic-based epidemiology can provide insight into the origins and spread of herbicide resistance mechanisms in weeds. We used kochia (Bassia scoparia) populations resistant to the herbicide glyphosate from across western North America to test the alternative hypotheses that (i) a single EPSPS gene duplication event occurred initially in the Central Great Plains and then subsequently spread to all other geographical areas now exhibiting glyphosate-resistant kochia populations or that (ii) gene duplication occurred multiple times in independent events in a case of parallel evolution. We used qPCR markers previously developed for measuring the structure of the EPSPS tandem duplication to investigate whether all glyphosate-resistant individuals had the same EPSPS repeat structure. We also investigated population structure using simple sequence repeat markers to determine the relatedness of kochia populations from across the Central Great Plains, Northern Plains and the Pacific Northwest. We found that the original EPSPS duplication genotype was predominant in the Central Great Plains where glyphosate resistance was first reported. We identified two additional EPSPS duplication genotypes, one having geographical associations with the Northern Plains and the other with the Pacific Northwest. The EPSPS duplication genotype from the Pacific Northwest seems likely to represent a second, independent evolutionary origin of a resistance allele. We found evidence of gene flow across populations and a general lack of population structure. The results support at least two independent evolutionary origins of glyphosate resistance in kochia, followed by substantial and mostly geographically localized gene flow to spread the resistance alleles into diverse genetic backgrounds

Effective Herbicide Options for Controlling Glyphosate-Resistant Palmer Amaranth in Roundup Ready 2 Xtend Soybean

Glyphosate-resistant (GR) Palmer amaranth has become a serious challenge for soybean producers in the mid-south and central United States, including Kansas. Field experi­ments were conducted at the Kansas State University Agricultural Research Center (KSU-ARC) near Hays, KS, and Kansas State University Ashland Bottoms (KSU-AB) research farm near Manhattan, KS, to determine the effectiveness of preemergence (PRE) and PRE followed by (fb) postemergence (POST) herbicide programs on GR Palmer amaranth control in Roundup Ready 2 Xtend soybean. The study site at Hays was infested with GR Palmer amaranth population prior to soybean planting; whereas, the Manhattan site had natural infestation of GR Palmer amaranth. Eleven treat­ments, including PRE alone and PRE fb POST-applied herbicides were investigated. All PRE treatments included Roundup PowerMax for control of other weed species, while POST treatments were mixtures of Roundup PowerMax and Engenia herbi­cides. A single PRE application of Fierce XLT and Panther PRO had ≥ 90% control of GR Palmer amaranth; whereas, control with Authority Elite and Zidua PRO did not exceed 83% at 6 weeks after POST (WAPOST). Combined over two locations, all PRE fb POST treatments had excellent control (≥ 96%) of GR Palmer amaranth at 6 WAPOST. No significant differences for soybean grain yield were observed among herbicide treatments at the Hays site; whereas, an approximate 10% increase in grain yield was observed with PRE fb POST vs. PRE alone programs at the Manhattan site. Based on these results, the two-pass programs (PRE fb POST) investigated in this research can be effectively used for season-long control of GR Palmer amaranth in Roundup Ready 2 Xtend soybean

Differential metabolic effects of oral butyrate treatment in lean versus metabolic syndrome subjects

Background: Gut microbiota-derived short-chain fatty acids (SCFAs) have been associated with beneficial metabolic effects. However, the direct effect of oral butyrate on metabolic parameters in humans has never been studied. In this first in men pilot study, we thus treated both lean and metabolic syndrome male subjects with oral sodium butyrate and investigated the effect on metabolism. Methods: Healthy lean males (n = 9) and metabolic syndrome males (n = 10) were treated with oral 4 g of sodium butyrate daily for 4 weeks. Before and after treatment, insulin sensitivity was determined by a two-step hyperinsulinemic euglycemic clamp using [6,6-2H2]-glucose. Brown adipose tissue (BAT) uptake of glucose was visualized using 18F-FDG PET-CT. Fecal SCFA and bile acid concentrations as well as microbiota composition were determined before and after treatment. Results: Oral butyrate had no effect on plasma and fecal butyrate levels after treatment, but did alter other SCFAs in both plasma and feces. Moreover, only in healthy lean subjects a significant improvement was observed in both peripheral (median Rd: from 71 to 82 μmol/kg min, p < 0.05) and hepatic insulin sensitivity (EGP suppression from 75 to 82% p < 0.05). Although BAT activity was significantly higher at baseline in lean (SUVmax: 12.4 ± 1.8) compared with metabolic syndrome subjects (SUVmax: 0.3 ± 0.8, p < 0.01), no significant effect following butyrate treatment on BAT was observed in either group (SUVmax lean to 13.3 ± 2.4 versus metabolic syndrome subjects to 1.2 ± 4.1). Conclusions: Oral butyrate treatment beneficially affects glucose metabolism in lean but not metabolic syndrome subjects, presumably due to an altered SCFA handling in insulin-resistant subjects. Although preliminary, these first in men findings argue against oral butyrate supplementation as treatment for glucose regulation in human subjects with type 2 diabetes mellitus