Partial characterization of phytoplasmas associated with lettuce and wild lettuce phyllodies in Iran

Phytoplasmas associated with lettuce phyllody (LP) and wild lettuce phyllody (WLP) in southern Iran were partially characterized by molecular analyses and host-range studies. Agents of both diseases were transmitted by Neoaliturus fenestratus , a leafhopper colonizing lettuce and wild lettuce, to lettuce, wild lettuce, sowthistle and periwinkle, but not to safflower, sunflower, calendula and sesame. Both phytoplasmas induced bud proliferation, virescence, phyllody and witches' broom in infected plants. Total DNA extracted from infected lettuce and wild lettuce or from vector tissues was subjected to PCR using phytoplasma-specific primer pair P1/P7 or nested PCR using P1/P7 followed by R16F2n/R16R2. PCR product of nested PCR (1·2 kbp) was subjected to restriction fragment length polymorphism (RFLP). RFLP analysis of nested PCR product identified the LP, WLP and N. fenestratus -associated phytoplasmas as members of the pigeon pea witches' broom group, 16SrIX. Phylogenetic analysis of the 16S rRNA gene sequence also clustered LP and WLP phytoplasmas with other known members of the 16SrIX group. While no significant differences could be detected between LP and WLP phytoplasmas, both isolates differed from Lebanese wild lettuce phyllody in molecular properties.     

Spastic paresis in a Poll Hereford heifer

A case of unilateral spastic paresis in a Poll Hereford heifer is described. The heifer could not actively flex the right stifle or hock and the toe just contacted the ground. There was cranial distortion and collapse of the distal tibial epiphysis and remodelling of the articular surfaces within the stifle and hock. There was moderately severe muscle atrophy, but a primary peripheral or central neuropathological lesion could not be found.     

Evaluation of brush cytology in the diagnosis of chronic intranasal disease in cats

Brush cytology was used as a diagnostic aid in 85 cats affected with chronic intranasal disease. Fifty-three of these cases, sampled over a five-year period, were included in this study, while the other cases were excluded due to poor cellularity of the cytological samples (nine cases) or a lack of histological or follow-up data (23 cases). Thirty-six brush samples were classified by cytology as inflammatory. Subsequent histological examination revealed a false negative diagnosis of neoplasia in six cats, two of which had malignant tumours (one adenocarcinoma and one lymphoma), the remaining four having benign tumours (two adenomas and two osteochondromas). Seventeen samples were classified by brush cytology as neoplastic. This was confirmed in 16 of these cases by histology or follow-up (nine epithelial malignant tumours, six lymphomas and one osteosarcoma). In the remaining case, a false positive diagnosis of lymphoma was made. The procedure had an overall 86.8 per cent (46/53) agreement between the diagnosis of inflammatory conditions versus neoplasia, with a sensitivity of 72.7 per cent, a specificity of 96.8 per cent, a predictive value of a positive test of 94.1 per cent and a predictive value of a negative test of 83.3 per cent.     

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.