Long-term effects of metal-containing farmyard manure and sewage sludge on soil organic matter in a fluvisol

Our aim was to establish the long-term effects of repeated applications after 20 y of organic amendments (farmyard manure at 10 t ha⁻¹ y⁻¹, and urban sewage sludge at two different rates, 10 t ha⁻¹ y⁻¹ and 100 t ha⁻¹ every 2 y) on the quality of a sandy and poorly buffered soil (Fluvisol, pH 6). Chemical characteristics and biodegradability of the labile organic matter, which is mainly derived from microbial biomass and biodegradation products of organic residues, were chosen as indicators for soil quality. The organic C content had reached a maximal value (30.6 g C kg⁻¹ in the 100 t sludge-treated soil), i.e. about 2.5 times that in the control. Six years after the last application, the organic C content and the microbial biomass content remained higher in sludge-treated soils than in the control. In contrast, the proportion of labile organic matter was significantly lower in sludge-treated soils than in manure-treated and control soils. The labile organic matter of sludge extracts appeared less humified than that of manure-treated and control soils.     

How the Soil Moves Upward in the Olive Orchards of NW Syria: Sustainability Analysis of a Local Innovation

This paper analyses a local innovation in response to intense soil degradation in olive orchards of north‐west Syria. Farmers developed a practice consisting of quarrying red clayey soil in valley bottoms and applying this soil to hillslope olive orchards with heavily degraded calcareous soils. A biophysical, economic and social analysis of the practice of soil application identified the opportunities and risks of this innovative soil management technique. On the basis of a pairwise comparison of nine adjacent treated and nontreated orchard plots, soil applications were found to increase soil depth by 36%, soil water availability by 28% and total available soil nutrients: potassium (+45%), nitrogen (+12%) and phosphorus (+6%). Olive yield increased by about 40%. A cost–benefit analysis found this practice to be economically viable within a large geographical area, and farmers scored the practice higher than alternative methods. A socio‐economic analysis revealed its widespread adoption among different farmer types. The positive results of soil applications at the farm level explain its fast adoption. However, potential risks – including the further depletion of soil resources and the transfer of soil‐borne diseases – limit the long‐term sustainability of this locally developed practice. Copyright © 2013 John Wiley & Sons, Ltd.     

Trophic overlap between non‐native brown bullhead (Ameiurus nebulosus) and native shortfin eel (Anguilla australis) in shallow lakes

We quantified trophic overlap between the invasive, non‐native catfish brown bullhead (Ameiurus nebulosus) and the New Zealand native shortfin eel (Anguilla australis) in four peat and riverine lakes using stable isotope (δ¹³C and δ¹⁵N) and gut content analyses. Across all lakes and fish sizes over the austral spring–summer period, shortfin eel guts were dominated numerically by fish prey (57% occurrence cf 42% in brown bullhead), while Diptera larvae were most commonly encountered in guts of brown bullhead (45% cf 14% in eels). Significant differences in % composition of animal contents in guts were detected between fish species and sampling occasions (n = 4) but not between lakes. In contrast, stable isotope signatures of brown bullhead and shortfin eel did differ significantly between lakes but not between sampling occasions, indicating enduring sources of nutrition despite apparently differing ingestion patterns over time. The R mixing model MixSIAR indicated that shortfins likely assimilated higher proportions of fish prey carbon compared to brown bullheads, which appeared to show greater assimilation of invertebrates, consistent with the results of gut content analyses. Isotopic niche regions, calculated in nicheROVER using probabilistic ellipses, indicated that shortfin eels occupied at least c.60% of brown bullhead trophic niche, which occupied less than 30% of eel trophic niche in all but one lake. These estimates suggest that brown bullhead has higher potential to influence shortfin eel nutrition than vice versa, or that a broad trophic niche occupied by eels provides resilience to the effects of overlapping consumption patterns with invasive omnivores.     

Simulation of optimal harvesting strategies for small-scale mixed-sex tilapia (Oreochromis shiranus Boulenger 1896) ponds using a bio-economic model

A cohort‐based bio‐economic biomass growth and economic model, validated with data from experiments conducted in Malawi, was used to identify an optimal harvesting strategy for mixed‐sex tilapia ponds. Three harvesting scenarios (baseline, economic optimum time +10 days and economic optimum time) were used. In each harvesting scenario four options were explored: (i) no further harvest, harvest every (ii) 60 days, (iii) 90 days and (iv) 120 days after initial harvest. The lowest simulated yield (487 kg ha⁻¹ year⁻¹) was obtained when no partial harvesting was carried out and fish were harvested after 365 days. Maximum yield (4416 kg ha⁻¹ year⁻¹) was obtained when partial harvests were carried out every 90 days starting with a first harvest of fish weighing 60 g or more at day 90. Maximum financial returns (US$2561 ha⁻¹ year⁻¹) were obtained when partial harvests were carried out every 120 days starting with the first harvest at day 90 and removing all fish ≥60 g. The model simulations indicate that mixed‐sex tilapia culture may be profitable for tilapia farmers in Africa where markets accept small (60–150 g)‐sized fish. The study further shows that a cohort‐based population growth model can be reliably incorporated in tilapia production models to simulate fish yields in mixed‐sex tilapia production systems. However, incorporation of intergenerational competition effects could improve the model's utility as a decision support tool for managing mixed‐sex tilapia production.     

Cytochrome P450 1 enzyme inhibition and anticancer potential of chromene amides from Amyris plumieri

Cytochrome P450 (CYP) enzyme inhibitory properties of six chromenylated amide compounds (CAs) from Amyris plumieri are described. Inhibition of CYP microsomes (CYP1A1, CYP1A2, CYP1B1, CYP2D6, CYP3A4 and CYP2C19) was monitored using a fluorescent assay. Potent inhibition was found against CYP1A1 with IC₅₀ and K_i for CA1 (acetamide), being the lowest at 1.547 ± 1.0 μM and 0.37 μM respectively, displaying non-competitive kinetics. The selectivity for CYP1A1 was increased in CA3 (butanamide), which also exhibited cytotoxicity against breast cancer cells, MCF7 with an IC₅₀ of 47.46 ± 1.62 μM. Structure-activity relationship studies provide insight at a molecular level for CAs with implications in chemoprevention and chemotherapy.     

Old and new association of Cotesia icipe (Hymenoptera: Braconidae) with alien invasive and native Spodoptera species and key stemborer species: implication for their management

BACKGROUND

Maize production in Africa is hindered by a myriad of biotic challenges, key among them being invasive and native lepidopteran stemborers. Recent invasion of the continent by fall armyworm, Spodoptera frugiperda, has further exacerbated the situation. Fortunately, Cotesia icipe was found to be very promising against S. frugiperda. However, the co-occurrence and interaction between S. frugiperda and the stemborers (Busseola fusca, Sesamia calamistis, and Chilo partellus) in maize agroecosystem may jeopardize the efficiency of C. icipe as a biocontrol agent of S. frugiperda. This study investigated the performance of C. icipe on S. frugiperda, Spodoptera littoralis and the stemborers. Specifically, the preference and acceptability of C. icipe to the host insects, the physiological suitability of the hosts for its development, and the effect of these hosts on the fitness parameters of the offspring were assessed.

RESULTS

Cotesia icipe accepted all the tested hosts, albeit with higher preference for Spodoptera species than for stemborers under multiple-choice tests. Also, the highest parasitism of up to 97% was recorded on S. frugiperda compared with parasitism on the stemborers of 43% in B. fusca. Moreover, physiological suitability and fitness traits (except for per cent female offspring) varied with host species, again being optimal on Spodoptera species.

CONCLUSION

Cotesia icipe demonstrated strong potential to control S. frugiperda in maize due to its high affinity for parasitization and developmental success in this host; and despite its non-specific parasitization, the presence of other hosts may not prevent its maximum control of S. frugiperda. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.     

Electrocardiographic findings in miniature schnauzers with syncope

Objective: The purpose of this study was to examine a population of miniature schnauzers exhibiting syncope as their primary presenting complaint and to correlate their electrocardiographic (ECG) findings with the criteria for the diagnosis of sick sinus syndrome (SSS) reported in the human and veterinary literature. Design: Retrospective study. Patients: Case records of 31 miniature schnauzers with syncope during the period 1996–2000 were reviewed. Measurements and results: This study supported two previous studies finding that females were more predisposed to ECG abnormalities associated with SSS than males. It was also noted that females were slightly older (10.1 years) when compared to males (8.9 years) at the time of diagnosis. A heart murmur was present in 61% of the dogs and this was most likely secondary to mitral valve endocardiosis and regurgitation. The primary rhythm disturbance seen was sinus arrest/sinoatrial block in 48.5% of the cases; sinus bradycardia was the second most common arrhythmia noted. Conclusion: In miniature schnauzers with syncope, SSS should be considered as a primary etiology if abnormal ECG findings are noted.     

Wheat (Triticum aestivum L.)‐based intercropping systems for biological pest control

Wheat (Triticum aestivum L.) is one of the most cultivated crops in temperate climates. As its pests are mainly controlled with insecticides that are harmful to the environment and human health, alternative practices such as intercropping have been studied for their potential to promote biological control. Based on the published literature, this study aimed to review the effect of wheat‐based intercropping systems on insect pests and their natural enemies. Fifty original research papers were obtained from a systematic search of the peer‐reviewed literature. Results from a vote‐counting analysis indicated that, in the majority of studies, pest abundance was significantly reduced in intercropping systems compared with pure stands. However, the occurrence of their natural enemies as well as predation and parasitism rates were not significantly increased. The country where the studies took place, the type of intercropping and the crop that was studied in the association had significant effects on these results. These findings show that intercropping is a viable practice to reduce insecticide use in wheat production systems. Nevertheless, other practices could be combined with intercropping to favour natural enemies and enhance pest control. © 2016 Society of Chemical Industry     

A novel aphid resistance locus in cowpea identified by combining SSR and SNP markers

The utility of combining simple sequence repeat (SSR) and single nucleotide polymorphism (SNP) marker genotyping was determined for genetically mapping a novel aphid (Aphis craccivora) resistance locus in cowpea breeding line SARC 1‐57‐2 and for introgressing the resistance into elite cultivars by marker‐assisted backcrossing (MABC). The locus was tagged with codominant SSR marker CP 171F/172R with a recombination fraction of 5.91% in an F₂ population from ‘Apagbaala’ x SARC 1‐57‐2. A SNP‐genotyped biparental recombinant inbred line population was genotyped for CP 171F/172R, which was mapped to position 11.5 cM on linkage group (LG) 10 (physical position 30.514 Mb on chromosome Vu10). Using CP 171F/172R for foreground selection and a KASP‐SNP‐based marker panel for background selection in MABC, the resistance from SARC 1‐57‐2 was introduced into elite susceptible cultivar ‘Zaayura’. Five BC₄F₃ lines of improved ‘Zaayura’ that were isogenic except for the resistance locus region had phenotypes similar to SARC 1‐57‐2. This study identified a novel aphid resistance locus and demonstrated the effectiveness of integrating SSR and SNP markers for trait mapping and marker‐assisted breeding.