Canola Crops Research Articles

Design, Synthesis, and Bioactivity of Novel 2-(Arylformyl)cyclohexane-1,3-dione Derivatives as HPPD Inhibitors.

4-Hydroxyphenylpyruvate dioxygenase inhibitors (Echinochloa crus-galli 1.13.11.27, HPPD) have gained significant popularity as one of the best-selling herbicides worldwide. To identify highly effective HPPD inhibitors, a rational design approach utilizing bioisosterism was employed to create a series of 2-(arylformyl)cyclohexane-1,3-dione derivatives. A total of 29 novel compounds were synthesized and characterized through various techniques, including IR, 1H NMR, 13C NMR, and HRMS. Evaluation of their inhibitory activity against Arabidopsis thaliana HPPD (AtHPPD) revealed that certain derivatives exhibited superior potency compared to mesotrione (IC50 = 0.204 μM). Initial herbicidal activity tests demonstrated that compounds 27 and 28 were comparable to mesotrione in terms of weed control and crop safety, with compound 28 exhibiting enhanced safety in canola crops. Molecular docking analyses indicated that the quinoline rings of compounds 27 and 28 formed more stable π-π interactions with the amino acid residues Phe-360 and Phe-403 in the active cavity of AtHPPD, surpassing the benzene ring of mesotrione. Molecular dynamics simulations and molecular structure comparisons confirmed the robust binding capabilities of compounds 27 and 28 to AtHPPD. This study provides a valuable reference for the development of novel triketone herbicide structures, serving as a blueprint for future advancements in this field.

Efficiency of nitrogen, gibberellic acid and potassium on canola production under sub-tropical regions of Pakistan

The global demand for crop production is rapidly growing due to the continued rise in world population. Crop productivity varies generally with soil nutrient profile and climate. The optimal use of fertilizers might help to attain higher crop yield in canola. To circumvent nutrient imbalance issues in soil, two separate field trials were conducted to determine (a) the best source of nitrogen (N) between ammonium sulfate (NH4)2SO4) and ammonium nitrate (NH4NO3), (b) significance of gibberellic acid (GA3) and potassium (K), in an attempt to enhance canola yield and yield attributes. Both experiments were carried out in randomized complete block design (RCBD) with three replicates. The nitrogen source in the form of NH4)2SO4 (0, 10, 20 and 30 kg/ha) and NH4NO3 (0, 50, 75 and 100 kg/ha) was applied in the rhizosphere after 3 and 7 weeks of sowing, referred to as experiment 1 (E1). In another separate experiment (E2), the canola crop was sprayed with four level of GA3 (0, 10, 15, 30 g/ha) and K (0, 2.5, 3.5, 6 g/ha) individually or in combination by using hydraulic spryer, 30 days after sowing (DAS). The data was collected at different growth stages of canola and analyzed statistically. The E1 trail showed that N fortification in the form of NH4NO3 (100 kg/ha) and (NH4)2SO4 (30 kg/ha) had a positive effect on the plant height, number of branches, fruiting zone, seed yield per plant, seed yield per hectare of canola except oil percentage. Moreover, canola plants (E2) also displayed a significant improvement on all studied features with high doses of GA3 (30 g/ha) and K (6 g/ha) individualy and in combined form. The correlation coefficient analysis of (NH4)2SO4 and NH4NO3 was highly significant to plant height, number of branches, fruiting zone, seed yield per plant, seed yield per hectare of canola In a nutshell, compared to both source of N, NH4NO3 was more efficient and readily available source of N. GA3 being a growth elicitor and potassium as a micronutrient serve as potential source to improve yield and to manage nutrient profile of canola.

Differential effects of soil conservation practices on arthropods and crop yields

AbstractMany agricultural management tactics, such as reduced tillage, aim to promote biodiversity and ecosystem services. Responses to such tactics can be context dependent, however, and differentially impact (i) functional groups of service‐providing organisms and (ii) crop yields. In canola (Brassica napus L., B. rapa L.) crop fields, we assessed how soil tillage and landscape context (amount of semi‐natural habitat within 1 km of each field) affected arthropod biodiversity and crop yield. We assessed effects of full (multiple tillage passes that leave soil surface bare), intermediate (tilled once and some stubble remains), or no (seed planted directly into last year's stubble) tillage on functional groups with unique diets and reproductive strategies: (i) herbivores, (ii) kleptoparasites, (iii) parasitoids, (iv) pollinators, and (v) predators. Effects of tillage and landscape context on arthropod abundance and diversity varied across functional groups. Pollinators responded strongest to tillage, benefitting from intermediate tillage. Predators and herbivores responded strongly to landscape context, as both were more abundant in landscapes with more semi‐natural habitat. Our results suggest that natural history differences among functional groups mediate effects of landscape context on biodiversity. However, variation in arthropod communities had little effect on canola crop yield. The effects of soil management practices on aboveground arthropods are complex, and practices thought to increase some aspects of agricultural sustainability may not be beneficial in other contexts. Identifying practices such as intermediate tillage that may increase soil quality and arthropod diversity is a key to designing agricultural ecosystems that will effectively benefit both biodiversity and human well‐being.

Plant growth regulator extracts from seaweeds promote plant growth and confer drought tolerance in canola (Brassica napus)

ABSTRACT Brassica napus, commonly known as canola, is an important oilseed crop in Canada contributing over $29.9 billion CAD to the Canadian economy annually. A major challenge facing Canadian canola is drought, which has become increasingly prevalent in recent years due to the changing climate. Research investigating novel agronomic techniques in mitigating drought is key to securing yields and sustainability in canola and other crops. One such technique is the use of bio-stimulant sprays to help offset biotic and abiotic stresses in plants through promoting stand establishment. Previous studies have shown that the application of seaweed extracts as bio-stimulant sprays to Brassicaceae has been successful in improving plant growth and development along with stress tolerance. However, this method has yet to be tested on canola. The organic nutrients that are waste products from processed seaweed help stimulate plant growth, yielding higher quality plants as a result. In association with Le Groupe Roullier, this study demonstrates that the Roullier extracts (RE) help increase plant growth characteristics and drought tolerance in canola when sprayed 3 times over a 3-week period. A high yielding but drought sensitive mutant of canola, d14 (developed through gene editing) was used for drought assays after 8 weeks of growth and where water was withheld for 6 days. Application of the REs prior to drought resulted in plants having enhanced survival rate and improved biomass retention indicating high drought tolerance. Subsequent RNA sequencing and gene ontological term analysis performed using RE treated plants in triplicates, revealed substantial levels of differential expression of growth-related genes along with stress-related genes. These REs elicited responses in plants that had previously only been achieved through gene editing and transgenic methodologies. Using bio-stimulant sprays provides a novel platform to promote beneficial agronomic traits, independent of genetic manipulation.

Characterization of a virulence factor in Plasmodiophora brassicae, with molecular markers for identification.

Symptom severity on differential host lines is currently used to characterize and identify pathotypes of Plasmodiophora brassicae, which is an obligate, soil-borne chromist pathogen that causes clubroot disease on canola (Brassica napus) and other brassica crops. This process is slow, variable and resource intensive; development of molecular markers could make identification of important pathotypes faster and more consistent for deployment of cultivars with pathotype-specific resistance. In the current study, a variant of gene 9171 was identified in the whole-genome sequences of only the highly virulent pathotypes of P. brassicae from around the world, including the new cohort of virulent pathotypes in Canada; its presence was confirmed using three KASP marker pairs. The gene was not present in the initial cohort of pathotypes identified in Canada. The putative structure, domains, and gene ontogeny of the protein product of gene 9171 were assessed using on-line software resources. Structural analysis of the putative protein produced by gene 9171 indicated that it was localized in the cytosol, and likely involved in cellular processes and catalytic activity. Identification of gene 9171 represents a potentially useful step toward molecular identification of the pathotypes of P. brassicae.

Novel quantitative trait loci from an interspecific Brassica rapa derivative improve pod shatter resistance in Brassica napus.

Pod shatter is a trait of agricultural relevance that ensures plants dehisce seeds in their native environment and has been subjected to domestication and selection for non-shattering types in several broadacre crops. However, pod shattering causes a significant yield reduction in canola (Brassica napus L.) crops. An interspecific breeding line BC95042 derived from a B. rapa/B. napus cross showed improved pod shatter resistance (up to 12-fold than a shatter-prone B. napus variety). To uncover the genetic basis and improve pod shatter resistance in new varieties, we analysed F2 and F2:3 derived populations from the cross between BC95042 and an advanced breeding line, BC95041, and genotyped with 15,498 DArTseq markers. Through genome scan, interval and inclusive composite interval mapping analyses, we identified seven quantitative trait loci (QTLs) associated with pod rupture energy, a measure for pod shatter resistance or pod strength, and they locate on A02, A03, A05, A09 and C01 chromosomes. Both parental lines contributed alleles for pod shatter resistance. We identified five pairs of significant epistatic QTLs for additive x additive, additive dominance and dominance x dominance interactions between A01/C01, A03/A07, A07/C03, A03/C03, and C01/C02 chromosomes for rupture energy. QTL effects on A03/A07 and A01/C01 were in the repulsion phase. Comparative mapping identified several candidate genes (AG, ABI3, ARF3, BP1, CEL6, FIL, FUL, GA2OX2, IND, LATE, LEUNIG, MAGL15, RPL, QRT2, RGA, SPT and TCP10) underlying main QTL and epistatic QTL interactions for pod shatter resistance. Three QTLs detected on A02, A03, and A09 were near the FUL (FRUITFULL) homologues BnaA03g39820D and BnaA09g05500D. Focusing on the FUL, we investigated putative motifs, sequence variants and the evolutionary rate of its homologues in 373 resequenced B. napus accessions of interest. BnaA09g05500D is subjected to purifying selection as it had a low Ka/Ks ratio compared to other FUL homologues in B. napus. This study provides a valuable resource for genetic improvement for yield through an understanding of the genetic mechanism controlling pod shatter resistance in Brassica species.

Determination of water-soluble carbohydrates by near-infrared spectroscopy for canola, maize, and sorghum stem fractions

Near infrared spectroscopy (NIRS) was evaluated as a rapid and non-destructive method for determining the concentration of water-soluble carbohydrates (WSC) in stem fractions for winter canola (Brassica napus L.), maize (Zea mays L.) and sorghum (Sorghum bicolor L. Moench) crops. For each crop at different growth stages, stem WSC concentration was determined using NIRS, and benchmarked against the anthrone reagent method, chemical lab analysis. Partial least squares regression was implemented to associate the WSC predicted via NIRS relative to those obtained by laboratory analysis. Spectral regions between 1100 and 1480 nm were critical for WSC determination. The predictive models resulted in coefficient of determinations of 0.93, 0.94, and 0.95, and a Root Mean Square Error of prediction of 10, 20, and 17 for winter-canola, maize and sorghum crops, respectively. The NIRS spectroscopy is a reliable method for WSC determination in stem tissues on these major field crops.

Growth and grain yield of canola overseeded on soybean

The overseeding technique allows the establishment of a crop before the harvest of an overseeded crop at the end of the cycle. It aims at making a better use of more favorable seasonal climatic conditions and the intensification of cultivation systems, with the possibility of obtaining another harvest in less time. This work aimed to verify if it is possible to establish the Brassica napus crop in overseeding with the phenological stages at beginning of grain filing (R5) and beginning of soybean physiological maturation (R7) in the Central region of the state of Rio Grande do Sul. The study was performed in a Humid Subtropical climate, in Santa Maria, RS. A randomized block design was used, in a 4 x 2 factorial arrangement with 4 replications, with four seed Brassica napus densities (3, 6, 12, and 18 kg ha-1) and two developmental stages of the soybean crop (R5 and R7), in addition to the control treatment sown in rows directly on the straw right after soybean harvest (3 kg ha-1- standard). The plant density, yield components, and grain yield were measured. The canola crop is not established when overseeded in the soybean stage R5. The seed density of 6 kg ha-1 achieved the recommended plant density for the canola overseeded in stage R7 of the soybean crop. The 6 kg ha-1 density stood out as the best treatment performed in the R7 stage of the soybean crop.

The Effect of Gamma Irradiation, Salinity and Nano-Fertilizer on the Biological Parameters of Brassica napus L. Cultivated in Iraq

Canola (Brassica napus L) is currently one of the most significant oily seeds. It has a variety of nutrients, and its oil is safe for people to ingest as well as medicinal properties that help to relieve the symptoms of a variety of disorders. Soil salinity is one of the major issues of decreasing canola crop productivity that correlated with declines in the photosynthetic potential, since salt levels that are damaging to crop growth affect large terrestrial regions around the world are seriously impaired by soil salinity this research focused on the capability of canola seeds to grow under saline environment before and after gamma irradiation. Also, the most recent study intended to employ nano-fertilizer in Iraq and characterize its influence on the chemical makeup of canola seeds. Simple technique employed as a tissue culture using ground water with different EC. Seeds treated by two gamma irradiation dose and grown over cotton irrigated with salty water. Field experiment was carried out in Al-zafraniya station in Baghdad, Iraq, to investigate the effect of khazra iron nano chelate fertilizer foliar application on one rapeseed variety for increasing yield and yield components. The native local variety pactol was more reliable than olifera var at germination rate, plant high, number of leave and root. Irradiation negatively affects the biological parameter of Canola seeds with capablity to germinate and developed. Percentage of fatty acids significantly differed between fertilizer treatments. The myristic (C14:0) ranged from 0.1±0.012 to 0.14±0.011, Palmitic (16:0) from 3.6±0.024 to 3.91±0.029, 3.91±0.029 from 1.5±0.11 to 1.7±0.012, Arachidic (20:0) from 0.6±0.038 to 0.84±0.065, Behenic (22:0) range from 0.3±0.0028 to 0.41±0.032, Lignoceric (24:0) from 0.2±0.012 to 0.27±0.018, Palmitoleic (16:1) from 0.2±0.010 to 0.26±0.0021, Oleic (18:1) from 61.6±5.78 to 67.8±5.91, 67.8±5.91 from 1.4±0.13 to 1.64±0.15, Erucic (22:1) from 0.2±0.014 to 0.23±0.019, Linoleic (18:2n-6) from 21.7±3.1 to 23.4±3.7, Alpha Linolenic (18:3n3) from 9.6±0.87 to 10.1±2.8, Total Saturated from 6.3±5.4 to 6.8±4.9, Total MUFA was in the rangier from 62.4±7.1 to 64.5±7.1 and Total PUFA range from 31.3±4.1 to 37.4±5.1 for conventional canola and nano canola oils respectively.

Comparing the Positive Impacts and Stress Induction by Polyethylene Glycol (PEG 6000) Variable Levels on Canola (Brassica napus L.) Growth, Yield, and Oil Contents.

Seed quality (i.e., emergence energy, viability, physical purity, size, weight) is a critical factor that influences the yield of crops. Poor seed quality can lead to reduced germination rates, lower plant populations, and, ultimately, lower crop yields. On the other hand, seed priming is suggested to be an effective technique for improving seeds germination and plant population. In this study, we investigated the effect of seed priming with polyethylene glycol (PEG) on the germination, growth, and yield of two varieties of canola, super canola, and sandal canola. The treatment plan includes five concentrations of PEG (i.e., 5, 10, 15, 20%), distilled water priming, and control (no priming). All of the treatments were applied in 3 replications following a completely randomized design. Our results showed that seed priming with 5%PEG (T2) significantly improved radicle length (50 and 36%), plant height (43 and 34%), chlorophyll a (44 and 43%), chlorophyll b (120 and 208%), and total chlorophyll (83 and 111%) compared to control in super canola and sandal canola, respectively. In particular, seed priming with 5%PEG resulted in the highest increase in protein contents (25 and 1.40%), oleic acid (26 and 40%), and linolenic acid (6 and 6%) compared to control in super canola and sandal canola, respectively. It is concluded that seed priming with 5%PEG is an effective treatment to improve the performance of canola crops in terms of seedling growth, yield, chlorophyll, protein, and oil content. More investigations are recommended as future perspectives using other canola varieties to declare 5% PEG as an effective treatment for canola for improvement in growth, oil, protein, and chlorophyll contents.

Characterization of Plasmodiophora brassicae pathotypes from western Canada in 2019–2020

Clubroot, caused by Plasmodiophora brassicae, is a major soilborne disease of canola (Brassica napus) on the Canadian Prairies. Most canola cultivars carry what is now referred to as ‘first-generation’ resistance, which represents the most widely used clubroot management tool. Unfortunately, new pathotypes of P. brassicae have emerged that can overcome this resistance. By 2018, 36 unique pathotypes of P. brassicae had been identified on the Prairies based on their virulence on the Canadian Clubroot Differential (CCD) set, with pathotypes 3A, 3D and 3 H being predominant. Since the virulence of P. brassicae populations can shift rapidly in response to host selection pressure, continued pathotype monitoring is important for resistance stewardship. Clubbed roots were collected from 133 canola crops (126 in Alberta, 6 in Saskatchewan, 1 in Manitoba) in 2019 and 127 crops (113 in Alberta, 13 in Saskatchewan, 1 in Manitoba) in 2020, and evaluated for their CCD pathotype designations. Twenty-five unique pathotypes were identified across the sampled crops over the two years of the study; these included seven novel pathotypes, six of which could overcome first-generation resistance (3C, 8 G, 8I, 9D, 9E and 9F). While pathotypes 3A, 3D and 3 H continued to be identified frequently in 2019 and 2020, several others, most notably pathotype 8E (virulent on hosts with first-generation resistance), had also become more common by 2020. The results indicate the continued emergence of new P. brassicae pathotypes on canola.

Fungicide protection of winter canola crops against the most common diseases

Goal. To investigate the effect of fungicides on limiting the development of the most common diseases of winter rapeseed in the Forest Steppe of Ukraine.
 Methods. Field (setting up experiments, damage records, harvesting), phytopathological (identification of pathogens), information-analytical (collection and analysis of literary sources), mathematical-statistical (processing of research results). The work was carried out on the experimental fields of the Oleksandriya SE EB of the Belotserkiv district of the Kyiv region. Fungicides with different active substances were studied: azoxystrobin + cyproconazole, flutriafol + tebuconazole, boscalid + dimoxystrobin, metalaxyl-M + mancozeb, prothioconazole + tebuconazole, tebuconazole.
 Results. The weather conditions of the growing season during the research years were characterized by high average daily air temperature and insufficient rainfall and did not contribute to the widespread spread of rapeseed diseases. Alternaria caused by fungi of the Alternaria genus (A. brassicae (Berk.) Sacc., A. brassicicola Wilts. (Schw.), A. alternata (Fr.) Keissler) had the greatest spread and development during the years of research. In some years, downy mildew (the causative agent of the fungus Perenospora brassicae Gaeum) and fusarium wilt (Fusarium oxysporum Schlecht.) were detected on rapeseed crops with a small degree of spread and development. Treatment of crops with fungicides limited the development of rapeseed diseases during the growing season by 2.3—4.0 times. The technical efficiency of fungicides against Alternaria was on average 57.2—78.5%, against downy mildew — 69.5—73.9%. The highest effectiveness against Alternaria was provided by the Impact T fungicide, k.s. (flutriafol, 75 g/l + tebuconazole, 225 g/l), 1.0 l/ha, against downy mildew — Amistar Extra 280 SC (azoxystro­bin, 200 + cyproconazole, 80), 1.0 l/ha. Limiting the development of diseases helped to increase its yield. With the use of fungicides, the yield of rapeseed was at the level of 1.61—1.83 t/ha against 1.38 in the control, i.e. it was 16.7—32.6% higher.
 Conclusions. The most common diseases of winter rape during the years of research in the Right Bank Forest Steppe zone of Ukraine were Alternaria, Peronosporosis and Fusarium wilt. The dominant position in all years was occupied by Alternaria, the prevalence of which was 100%. The investigated fungicides had an effective effect on limiting the development of diseases and contributed to an increase in crop yield.

Landscape Effects on the Cabbage Seedpod Weevil, Ceutorhynchus obstrictus (Coleoptera: Curculionidae), and on Its Parasitoid, Trichomalus perfectus (Hymenoptera: Pteromalidae), in Canola

The cabbage seedpod weevil (CSW), Ceutorhynchus obstrictus, an exotic pest accidentally introduced in North America in 1931, spread all over this continent and is now a major pest of canola crops. One of its main natural enemies in Europe, Trichomalus perfectus, was observed in eastern Canada in 2009. This study aimed to evaluate the landscape influence on CSW infestation and abundance and on T. perfectus parasitism in Quebec to understand the optimal conditions to potentially release this parasitoid in the Canadian Prairies. Field research was conducted in 19 to 28 canola fields per year, from 2015 to 2020, among eight Quebec regions. CSW was sampled by sweep net during canola blooming and parasitoids by collecting canola pods kept in emergence boxes until adults emerge. Infestation and parasitism calculations were based on pod emergence holes. For analysis, 20 landscape predictors were considered. Results show that CSW infestation and abundance increased if there were more roads and cereal crops in the landscapes. Meanwhile, T. perfectus parasitism decreased when hedgerows length and distance from water were longer. However, it increased when landscape diversity and average crop perimeter-to-area ratio were higher, and along with more hay/pastures and soybean crops. This study's results highlight that these four landscape predictors could provide more resources and overwintering areas, promoting greater efficiency of T. perfectus to control the CSW.

Photothermal Quotient Describes the Combined Effects of Heat and Shade Stresses on Canola Seed Productivity

There is evidence of the negative effects on canola seed yield caused by shading (SH) and high temperature stress (HT) separately, but the combined effect of both stresses has not been studied. This work aimed to (i) evaluate the effects of SH and HT stresses, alone and combined, on floral development, seed yield and quality, (ii) quantify the resulting effect (additive, synergistic, antagonistic) of combined stresses, and (iii) examine the utility of the photothermal quotient (PTQ, solar radiation/temperature ratio) to predict seed yield in stressed canola crops. Two field experiments were performed in Buenos Aires (Argentina) applying HT daytime temperature stress (25–30 °C from 1000 to 1500 h), SH (−80% irradiance), and SH + HT combined stresses, with C unstressed (20 °C and 100% irradiance) crops. Long and short duration SH and HT strongly affected floral development (fewer flowers and pods, with smaller ovules) and seed yield (reduction from −40 to −90% respect to C). Combined SH + HT exhibited detrimental synergistic effects on seed yield and oil concentration for long duration stresses, whereas antagonistic effects were mainly observed for short stresses. We conclude that the PTQ (cumulative from 100 to 500 °Cd after flowering) summarizes adequately the detrimental effects of combined post-flowering abiotic stresses on canola seed productivity.

Investigation of an effective acid pre-treatment method for the valorisation of Canola fines

Canola fines are the straw-like material and other residues removed from incoming Canola crops before processing for seed oil. In South Africa, this lignocellulosic biomass is abundant and non-seasonal, making it an ideal substrate for recovery of sugars for valorization to higher value products. Pre-treatment for release of sugars from lignocellulose should be optimized for a given substrate. In this study, mechanical pre-treatment to reduce the size of Canola fines was followed by: (i) steam-assisted acid pre-treatment (0–2% H2SO4 % v/v) at different temperatures (20–55 °C), and biomass loading rates (2–8% w/v), and (ii) enzyme hydrolysis, using a central composite experimental design approach. The sugars in the hydrolysates obtained from stages (i) and (ii) were measured quantitatively and qualitatively as outputs that were used to assess process efficiency and to obtain predictive models. The raw and spent Canola fines from each phase were fully characterized in terms of chemical and structural changes at each stage of pre-treatment.The Canola fines contained 23.0% w/w lignin, 21.4% w/w cellulose, and 15.9% w/w hemicellulose. The maximum yield of total sugars after steam-assisted acid hydrolysis (18.6% w/w) was increased after enzyme hydrolysis (28.3 % w/w) and was higher than reported for other studies pre-treating rapeseed and Canola straws (10.2–11.8% w/w). The sugar profiles in the hydrolysates after steam-assisted acid hydrolysis (xylose>arabinose>glucose) differed from those obtained after acid-assisted enzyme hydrolysis (xylose>glucose>cellobiose>arabinose). The microscopic and chemical analyses of the Canola fines showed sequential breakdown of the lignin, cellulose, and hemicellulose, with some lignin still intact at the end of the pre-treatment. For application of this technology, no heating would be required for acid pre-treatment as temperature was not a significant variable. In addition, the optimal H2SO4 concentration was low (1.7% v/v), minimizing the use of hazardous chemicals as well as the risk of releasing microbial and/or enzyme inhibitors during the process. Enzyme hydrolysis should only be required if the downstream application requires higher sugar concentrations and/or different sugar profiles.

Effect of three crop rotations and four residue levels on canola and bean grain yield and residue production

AbstractCrop rotation in agriculture can lead to increased crop productivity in the rotation and improved soil fertility as a result of residue incorporation. Unfortunately, residue incorporation is not a common practice in crop production systems under the Mediterranean regime, largely due to the lack of information on the effect of the follow-up crops. Therefore, this study was conducted with six biannual rotations (bread wheat–canola, bread wheat–bean, durum wheat–canola, durum wheat–bean, corn–canola and corn–bean) using four residue incorporation levels (0, 50, 100 and 200%) in an Andisol in south central Chile. Grain yield and residue production were evaluated in the canola and bean crops 5 years after initiating crop rotation. The previous crop affected canola grain yield and residue production, which were both higher after corn. Meanwhile, the residue incorporation level had a slight effect on residue production after bread wheat. Only bean grain yield was affected by the previous crop, which was higher after the durum wheat and corn crops. The residue incorporation has marginally affected residue production after bread wheat. Finally, residue incorporation at different levels under the conditions of the present experiment had a minimal effect on bean and canola residue production following the bread wheat crop. The best crop rotation for canola grain yield was corn–canola, which produced 0.54 Mg/ha (18.3%) higher yield than the average of the other two rotations. The best crop rotation for achieving higher bean grain yield was corn–bean, which yielded 0.52 Mg/ha (12.3%) higher than the average of the other two rotations.

P450-mediated resistance in Myzus persicae (Sulzer) (Hemiptera: Aphididae) reduces the efficacy of neonicotinoid seed treatments in Brassica napus.

The prophylactic use of seeds treated with neonicotinoid insecticides remains an important means of controlling aphid pests in canola (Brassica napus) crops in many countries. Yet, one of the most economically important aphid species worldwide, the peach potato aphid (Myzus persicae), has evolved mechanisms which confer resistance to neonicotinoids, including amplification of the cytochrome P450 gene, CYP6CY3. While CYP6CY3 amplification has been associated with low-level resistance to several neonicotinoids in laboratory acute toxicity bioassays, its impact on insecticide efficacy in the field remains unresolved. In this study, we investigated the impact of CYP6CY3 amplification on the ability of M. persicae to survive neonicotinoid exposure under laboratory and semi-field conditions. Three M. persicae clones, possessing different copy numbers of CYP6CY3, were shown to respond differently when exposed to the neonicotinoids, imidacloprid and thiamethoxam, in laboratory bioassays. Two clones, EastNaernup209 and Osborne171, displayed low levels of resistance (3-20-fold), which is consistent with previous studies. However, in a large-scale semi-field trial, both clones showed a surprising ability to survive and reproduce on B. napus seedlings grown from commercial rates of neonicotinoid-treated seed. In contrast, an insecticide-susceptible clone, of wild-type CYP6CY3 copy number, was unable to survive on seedlings treated in the same manner. Our findings suggest that amplification of CYP6CY3 in M. persicae clones substantially impairs the efficacy of neonicotinoid seed treatments when applied to B.napus. These findings highlight the potentially important real-world implications of resistances typically considered to be 'low level' as defined through laboratory bioassays. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Novel resistances provide new avenues to manage Alternaria leaf spot (Alternaria brassicae) in canola (Brassica napus), mustard (B. juncea) and other Brassicaceae crops.

Alternaria leaf spot (Alternaria brassicae) can be a devastating disease in canola (Brassica napus) and mustard (B. juncea) but there are no highly effective host resistances available. Screening of 150 diverse Brassicaceae varieties under glasshouse conditions highlighted important novel resistances, in particular, Camelina sativa 4076 and Diplotaxis erucoides Wasabi Rocket with complete resistance across disease assessment parameters [leaf incidence (%LDI), severity (%LAD), consequent defoliation (%LCI)]. Next most resistant were C. sativa CSA (%LDI 0.6; %LAD 0.4), 4144 (%LDI 1.2; %LAD 0.5), 405 (%LDI 1.7; %LAD 0.7), C. sativa 3274 (%LDI 2.5; %LAD 0.8), Carrichtera annua CAN3 (%LDI 7.7; %LAD 4.0) and Sisymbrium irio London Rocket (%LDI 2.1; %LAD 0.8), all with %LCI values of 0. Other genotypes showing high level resistance included S. erysimoides SER 4 (%LDI 11.8; %LAD 5.6; %LCI 0), D. cardaminoides wild rocket (%LDI 15.5; %LAD 7.2; %LCI 0), and showing moderate resistance were Brassica carinata ML-EM-1 (Rungwe), B. insularis Moris, B. napus ZY006, B. oxyrrhina BOX1, B. oleracea var. capitata Sugarloaf, B. tournefortii CN01-104-2 and Sinapis alba Concerta with %LDI 21.6-29.8, %LAD 12.8-21.0 and %LCI 0-5.7. In particular, B. napus ZY006 for canola and B. oleracea var. capitata cv. Sugarloaf can now be directly utilized, i.e., without crossing impairment, for Brassica species and vegetable breeding programs, respectively. While all B. juncea genotypes were susceptible, there were some less susceptible varieties from India in comparison with genotypes from Australia or China. The most susceptible test genotype was Rapistrum sativus (%LDI 89.4; %LAD 83.9; %LCI 71.0), highlighting the value of the resistances identified. These findings not only highlight a range of novel resistances against A. brassicae for canola/mustard and other diverse Brassicaceae breeding programs to develop resistant commercial varieties, but also emphasize highly susceptible varieties to avoid in both breeding programs and commercial situations conducive to Alternaria leaf spot.

Diverse systems and strategies to cost-effectively manage herbicide-resistant annual ryegrass (Lolium rigidum) in no-till wheat (Triticum aestivum)-based cropping sequences in south-eastern Australia

Context Herbicide-resistant annual ryegrass (Lolium rigidum; ARG) is a major weed of commercial significance globally, including no-till wheat-based production systems in south-eastern Australia. Aims To compare the cost-effectiveness of different crop sequences and intensities of weed management to control ARG in rainfed grain production. Methods Two on-farm studies in southern New South Wales, Australia, compared the effect of combinations of 3-year crop-sequence options (continuous wheat, 1- or 2-years of break crops), conservative or aggressive weed-control measures, hay cuts, legume brown manure (BM), and/or weed-free winter fallow on in-crop ARG infestations and soil seedbanks. Gross margins were calculated for each combination of treatments to compare system economic performance. Key results Double-breaks consisting of two consecutive broadleaf crops, or canola–cereal hay, were frequently the most profitable and effective ARG control strategies. Single canola or lupin crops, BM, cereal hay, and fallow all significantly reduced subsequent in-crop ARG and seedbank numbers compared with continuous wheat. Aggressive in-crop control measures in wheat were more expensive than those applied to break crops. Gains in ARG control could be lost by a single year of poor weed control. Conclusions High levels of control (>95%) over three consecutive seasons are required to reduce ARG seedbanks, and this is most cost-effectively achieved with diverse crop sequences. Implications Farmers with high populations of ARG can reduce seedbanks by growing three crops sequentially that achieve complete weed seed control. This must be followed with ongoing high levels of control in subsequent years to keep ARG seedbanks low.

Honeydew associated with four common crop aphid species increases longevity of the parasitoid wasp, Bracon cephi (Hymenoptera: Braconidae)

Abstract The absence of sugar resources can be an important factor in limiting the success of parasitoids as biological control agents. Restoring vegetation complexity within agricultural landscapes has thus become a major focus of conservation biological control efforts, with a traditional emphasis on nectar resources. Aphid honeydew is also an important source of sugars that is infrequently considered. We carried out a laboratory experiment to examine the potential effects of honeydew from six different aphid species by crop species combinations on the longevity of Bracon cephi Gahan (Hymenoptera: Braconidae), the most important biological control of the wheat stem sawfly, Cephus cinctus Norton (Hymenoptera: Cephidae), a major pest of wheat in the northern Great Plains of North America. The benefits of honeydew for parasitoid longevity varied significantly among different aphid and crop species, illustrating the complexity of these interactions. However, honeydew produced by four aphid species commonly found in wheat, pea, and canola crops significantly increased the longevity (by two- to threefold) of the parasitoid. The study suggests that honeydew provisioning could be an important mechanism underlying the benefits of crop diversification to support biological control that merits further research.