Changes in the herbicide sensitivity and competitive ability of Abutilon theophrasti over 28 years: Implications for hormesis and weed evolution

BACKGROUND

The potential of weed species to respond to selection forces affecting the evolution of weedy traits such as competitive ability is poorly understood. This research characterized evolutionary growth changes in a single Abutilon theophrasti Medik. population comparing multiple generations collected from 1988 to 2016. A competition study was performed to understand changes in competitive ability, and a herbicide dose–response study was carried out to assess changes in sensitivity to acetolactate synthase-inhibiting herbicides and glyphosate over time.

RESULTS

When grown in monoculture, A. theophrasti biomass production per plant increased steadily across year-lines while leaf number decreased. In replacement experiments, A. theophrasti plants from newer year-lines were more competitive and produced more biomass and leaf area than the oldest year-line. No clear differences in sensitivity to imazamox were observed among year-lines. However, starting in 1995, this A. theophrasti population exhibited a progressive increase in growth in response to a sublethal dose of glyphosate (52 g a.e. ha⁻¹), with the 2009 and 2016 year-lines having more than 50% higher biomass than the nontreated control.

CONCLUSION

This study demonstrates that weeds can rapidly evolve increased competitive ability. Furthermore, the results indicate the possibility of changes in glyphosate hormesis over time. These results highlight the importance of the role that rapid (i.e., subdecadal) evolution of growth traits might have on the sustainability of weed management strategies. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.     

Prevalence and risk factors for anti-Toxoplasma gondii antibodies in goats of the Seridó Oriental microregion, Rio Grande do Norte state, Northeast region of Brazil

The prevalence and risk factors for anti-Toxoplasma gondii antibodies were investigated in goats of the Seridó Oriental microregion, Rio Grande do Norte state, Northeast region of Brazil. Three hundred and sixty-six blood samples from goats collected by jugular venopuncture were used. For the serologic diagnosis of Toxoplasma gondii infection, the indirect fluorescent-antibody test (IFAT) with cut-off value 1:64 was carried out. The prevalence of anti-T. gondii antibodies was 30.6% [95% CI=25.9-35.6%] with titers ranging from 1:64 to 1:16,384. The multivariate logistic regression analysis showed that the risk factors associated to anti-T. gondii antibodies were presence of cats in the herd, extensive/semi-intensive management systems and lack of mineral supplementation.     

Egg production responses of hens given a complete mash or unground grain together with concentrate pellets

Thirty‐three light hybrids aged 11 months were caged individually and fed for S weeks according to three regimes, viz. A, a conventional mash ad libitum; B, a mixture of whole wheat, barley and kibbled maize ad libitum in the morning, with concentrate pellets ad libitum in the afternoon; or C, ad libitum the same grain mixture together with concentrate pellets and oystershell grit in the ratio 70 : 23 : 7 so that the nutritive value of the complete diet was similar to that of the conventional mash. The concentrate pellets used in the two regimes differed. Those used in regime B contained ground limestone while those used in regime C did not.

Egg production was similar on the three regimes (74.8, 74.7 and 74.5% respectively) . Food intake was lowest on regime C and highest on regime B, although the intakes of metabolisable energy were very similar on the three regimes. Compared with the results obtained with the conventional mash diet (regime A), the conversions of food and dietary protein to eggs were lower on regime B but higher on regime C.     

Construction of a microarray specific to the chicken immune system: profiling gene expression in B cells after lipopolysaccharide stimulation

The objective of this study was to profile gene expression in cells of the chicken immune system. A low-density immune-specific microarray was constructed that contained genes with known functions in the chicken immune system, in addition to chicken-expressed sequence tags (ESTs) homologous with mammalian immune system genes, which were systematically characterized by bioinformatic analyses. Genes and ESTs that met the annotation criteria were amplified and placed on a microarray. The microarray contained 84 immune system gene elements. As a means of calibration, the microarray was then used to examine gene expression in chicken B cells after lipopolysaccharide stimulation. Differential gene expression was observed at 6, 12, and 24 h but not at 48 h after stimulation. The results were validated by semiquantitative polymerase chain reaction. The microarray showed a high degree of reproducibility, as demonstrated by intra- and interassay correlation coefficients of 0.97 and 0.95, respectively. Thus, the low-density microarray developed in this study may be used as a tool for monitoring gene expression in the chicken immune system.     

The effects of cold stress on neonatal calves. II. Absorption of colostral immunoglobulins.

Newborn calves were subjected to cold stress and made hypothermic by immersion in water at 15 to 17 degrees C. Cold stress delayed the onset and significantly decreased (P less than 0.05) the rate of absorption of immunoglobulins (IgM, IgG1 and IgG2) up to 15 hours after first feeding of pooled colostrum. However, the net absorption of colostral immunoglobulins was not affected. The possible deleterious effect of cold stress on absorption of colostral immunoglobulins by newborn calves under range conditions is discussed.     

Spindle cell sarcoma in the kidney of a dog

A spindle cell sarcoma involving the left kidney was diagnosed in a 14-year-old male Basenji. Radiography and ultrasonography were used to define the extent and location of the mass. Metastatic disease was not detected. An 8 x 5-cm mass, involving the left kidney, was resected by performing nephroureterectomy. Signs of metastasis were not detected at 3 and 6 months after surgery. Shortly after the 6-month examination, the dog was euthanatized because of perceived signs of pain attributable to cervical disk disease. Postmortem examination was not performed. Histologic examination consisted of use of hematoxylin and eosin, Masson trichrome, and van Gieson stains, and 4 immunoperoxidase techniques. On the basis of the histologic findings, the final diagnosis was spindle cell sarcoma, with the 2 most likely possibilities being leiomyosarcoma and fibrosarcoma.     

The photoperiodic effect of ahemeral light‐dark cycles which entrain circadian rhythms

1. A 27‐h cycle of light and dark provides a greater gonadotrophic stimulus to the laying fowl, as judged by sexual maturity and rate of lay, than a 24‐h cycle incorporating the same photoperiod.

2. An hypothesis put forward to account for these effects states that Effective Photoperiod equals p + c – b, where p = actual photoperiod, c = cycle length and b = the period of the endogenous biological clock.

3. Two experiments designed to test this hypothesis have yielded results which are consistent with it.

4. A poultryman who uses an ahemeral cycle to alter egg weight or shell thickness and then wishes to transfer his flock back to a 24‐h cycle should calculate the difference between the two cycle lengths and then add this quantity to the prevailing photoperiod to find the appropriate amount of light to be used in the 24‐h cycle.