Prabhath Lokuruge’s research while affiliated with Agriculture and Agri-Food Canada and other places

Organic crop production relies mostly on legumes for N input. Intercropping of organic legumes with more competitive crops might provide an alternative to the poor weed suppression and disease susceptibility of legumes. It might also be expected that such intercropping could be of benefit to crops grown in the subsequent year through increased N from the preceding intercropped legume, and lower weed growth due to the more competitive companion. The objective of this study, conducted under drier than average conditions in a semiarid region of the Canadian Prairies, was to determine how organic intercrops of legumes with a cereal or oilseed at different ratios would affect soil nutrients the next spring, weed levels, and the productivity and quality of the following durum wheat [Triticum turgidum L. ssp. durum (Desf.) Husn.]. Results from 2018 to 2019 showed that intercropping had a negligible impact on Olsen P and extractable K. Soil NO3‐N (>15‐cm deep) was lowest following the lentil (Lens culinaris Medik.)–mustard (Sinapis alba L.) intercrops and mustard monoculture, which was reflected in lower growth of the durum wheat. Conversely, some of the pea (Pisum sativum L.)–oat (Avena sativa L.) intercrops and the oat and all legume monocultures resulted in higher durum wheat biomass and grain yield, with their highest values observed after the checks summerfallow and forage pea manure. Weeds tended to have lower densities after the intercrops than the grain legume monocultures. Nutrient concentration in plant tissue suggested that weeds could be a greater source of soil nutrients than crops.

Intercropping, the growing of more than one crop at the same time within the same land area, could be a sustainable method of crop production in semiarid regions, which could increase biodiversity, and productivity and quality of crops compared to monocultures. This may be of significance under limited N, such as in organic agriculture, and could be an alternative to green manure. An organic study was conducted in the semiarid Canadian Prairie in drier than average years (2017–2018) to determine if intercropping legumes with non‐legumes could reduce weeds and increase grain yield and quality of crops at different seeding rate ratios. Intercrops examined were lentil (Lens culinaris Medik.)–yellow mustard (Sinapis alba L.), and field pea (Pisum sativum L.)–oat (Avena sativa L.), at three seeding rate ratios, and their respective monocultures. Weed density was lower in the pea–oat intercrop than the pea monoculture, while weed biomass was lower in the lentil–mustard intercrop than the lentil monoculture. Legumes, when intercropped even at monoculture ratios, had lower aboveground biomass and grain yield than their monocultures, with pea showing higher tolerance than lentil to competition with its companion. Total biomass and grain yield were accounted for mostly by the non‐legumes, which performed better than expected based on their seeding ratios. Mustard grown with lentil appeared to be more competitive than oat grown with pea. Grain weight of oat was higher in all intercrops with pea than in its monoculture, while grain protein of pea was higher when intercropped with oat than in its monoculture.

The agronomic and environmental benefits of diversified cropping systems have been well documented in the Canadian prairies. However, little is known about the profitability of diversified rotations with oilseeds, cereals, legumes, and specialty crops. This study consisted of two 5-year (2018–2022) experiments carried out at four sites in Saskatchewan and Alberta. Treatments were arranged in a randomized complete block design with four replicates. Net return (NR) was defined as total revenue minus total costs. Results showed diversified sequences with Oriental mustard, red lentil, yellow field pea, and yellow mustard had higher NR than continuous wheat and wheat with chemical fallow sequences. Moreover, sequences diversified with quinoa, yellow mustard, field pea, and wheat showed high NR across all sites. Wheat after chemical fallow in the wheat with chemical fallow sequence (wheat–wheat–chemical fallow–wheat–wheat) had high NR; however, this did not compensate for the loss of NR in the chemical fallow phase, resulting in the lowest NR. The inclusion of industrial, oriental, and yellow mustard in sequences with wheat and field pea decreased nitrogen cost by 30% compared to a continuous wheat sequence, concluding that such sequences not only improved NRs but also showed a significant reduction in nitrogen requirement costs.

The performance of cropping systems is a function of crop and management practice interaction in a given growing environment. However, the critical factors affecting productivity remains unclear under varying climate conditions. We conducted a 5 year study at six sites in western Canada to identify the critical factors affecting the productivity, standardized as protein-based yield (PBY), and quantify the relationships between yield and critical factors. We tested six crop rotations, including conventional system (Control), pulse- or oilseed-intensified system (Intensified), diversified system (Diversified), market-driven system (Market-driven), high-risk and potentially high reward system (High-risk), and soil-health enhanced system (Soil-health). The importance index and structural equation modeling were used to identify key factors and explore the underlying relationships among them. Results showed that Market-driven and Diversified rotations outperformed the Control by 2%–6% in PBY, while Soil-health and High-risk yielded 23%–26% lower than the Control. Relative to the Control, all rotations showed an increase trend in PBY over time, with Diversified rotations increasing 13%–28% faster than Market-driven and Intensified rotations. Precipitation and nitrogen (N) management are the primary factors affecting cropping system productivity, explaining 25% and 21% yield variations, respectively. Structural equation modeling analysis revealed that precipitation had a significant indirect effect on yield through affecting biological N fixation of pulse crops, in addition to a significant direct effect. Increasing pulse frequency and rotation complexity mitigated PBY loss by 10%–24% during low rainfall seasons. We recommend integrating pulse crops into cropping systems to enhance N management and mitigate yield loss in low precipitation regions.

The antagonistic activities of three potential biocontrol agents (BCAs), Clonostachys miodochialis, C. rosea, and Minimedusa polyspora, were tested in vitro against the target fungi Fusarium acuminatum, F. avenaceum, F. equiseti, F. graminearum, and Cochliobolus sativus. In vitro dual-culture assay revealed that the BCAs were able to inhibit the mycelial growth of most of the target fungi, with the most common mode of action being mycoparasitism. After 5 d of incubation, depending on the host-parasite interface, biotrophic mycoparasitism was observed via attachment structures on F. avenaceum, F. equiseti, and C. sativus. Haustoria and appressoria were formed by C. miodochialis and M. polyspora on F. avenaceum and C. sativus, respectively. Clamp-like structures were also produced by both BCAs, depending on the host fungus. Clonostachys rosea formed only contact points on its hosts. Coiling structure was observed with C. rosea and M. polyspora occasionally in pure culture but more abundantly in the dual-culture assay. After an additional 3 to 5 d of incubation, the BCAs started damaging their host cells. Asexual fruiting bodies of the BCAs spread necrotrophically on F. acuminatum and F. graminearum and began destroying their mycelia after the initial 5 d of incubation. Furthermore, mycelial dissolution of F. acuminatum by an excreted substance was observed at a distance before direct contact with C. miodochialis. The diffuse metabolite assay revealed that the highest inhibition of the three BCAs was on C. sativus and their least effectiveness was observed on F. graminearum. Overall, these results provide evidence that C. miodochialis, C. rosea, and M. polyspora are potential candidates for biological control of the tested target fungi. This constitutes the first report that these three BCAs are able to establish an initial biotrophic relationship followed by a necrotrophic lifestyle. In addition, C. miodochialis has not previously been reported as a BCA.

There has been a steady expansion in organic production in the Canadian Prairies because of higher consumer demand. Thus, increasing the sustainability of organic systems would be important. An organic trial was conducted in the semi‐arid Prairies (2010–2015) with two tillage intensities (low vs. high) in a simplified [spring wheat (Triticum aestivum L.)–forage pea (Pisum sativum L.) green manure (GM)] and a diversified (spring wheat–oilseed–pulse–GM) rotation. In 2013–2015, the impact of these systems on root rot was examined on spring wheat, pulses, and GM crops. Several Fusarium spp. were more abundant in GM and pulses than spring wheat, suggesting that they could be a source of inoculum, especially of F. avenaceum (Fr.:Fr.) Sacc. (teleomorph Gibberella avenacea Cook), for Fusarium diseases in cereals including Fusarium head blight. Under different environments, tillage–rotation systems had an impact on root disease and fungal populations, some of which have biocontrol capabilities. There was no difference among systems for root rot in forage pea, while the low tillage‐diversified rotation had the lowest root rot in spring wheat but was associated with more Fusarium spp. For all crops, most Fusaria were not associated with root rot severity. Cochliobolus sativus (Ito & Kurib.) Drechs. ex Dast. [anamorph Bipolaris sorokiniana (Sacc.) Shoemaker] accounted the most for root rot in spring wheat and was favored by intensive tillage and simplified rotations. The Shannon diversity index (H') of fungal species in spring wheat was higher in the diversified rotation under both tillage intensities than when spring wheat alternated with GM in the simplified rotation, especially under high tillage. In forage pea, H' was higher than in spring wheat, but did not differ among tillage–rotation systems.

Costs of production and organic price premiums are defining factors influencing the economic viability of organic crop production systems. Different agronomic practices, such as crop rotation and tillage intensity, are known to affect the economic performance of the production systems. The aim of this study was to compare the impact of two crop rotation sequences (simplified and diversified) and two levels of tillage intensity (high and low) on the cost of production, gross return and gross margin of crops when grown under organic management in the semi-arid Brown soil zone of the Canadian Prairies. The 2-year simplified rotation sequence consisted of forage pea ( Pisum sativum L.) grown as a green manure followed by hard red spring wheat (HRSW) ( Triticum aestivum L.), while the 4-year diversified rotation sequence was forage pea green manure followed by flax ( Linum usitatissimum L.) or yellow mustard ( Sinapis alba L.), field pea or lentil ( Lens culinaris L.) and HRSW. Our hypothesis that a more diversified crop rotation would increase profitability over a traditional simplified crop rotation was supported by the findings. However, the findings did not support our hypothesis that reducing tillage intensity, and the combination of tillage reduction and diversified crop rotation through a synergetic response, would further enhance profitability. Analysis of the breakeven prices and breakeven yields for crops indicated the importance of adopting diversified crop rotations and choosing crops with high organic price premiums as means to maximize the long-term profitability of organic cropping systems.

The durum wheat line DT696 is a source of moderate Fusarium head blight (FHB) resistance. Previous analysis using a bi-parental population identified two FHB resistance quantitative trait loci (QTL) on chromosome 5A: 5A1 was co-located with a plant height QTL, and 5A2 with a major maturity QTL. A Genome-Wide Association Study (GWAS) of DT696 derivative lines from 72 crosses based on multi-environment FHB resistance, plant height, and maturity phenotypic data was conducted to improve the mapping resolution and further elucidate the genetic relationship of height and maturity with FHB resistance. The Global Tetraploid Wheat Collection (GTWC) was exploited to identify durum wheat lines with DT696 allele and additional recombination events. The 5A2 QTL was confirmed in the derivatives, suggesting the expression stability of the 5A2 QTL in various genetic backgrounds. The GWAS led to an improved mapping resolution rendering the 5A2 interval 10 Mbp shorter than the bi-parental QTL mapping interval. Haplotype analysis using SNPs within the 5A2 QTL applied to the GTWC identified novel haplotypes and recombination breakpoints, which could be exploited for further improvement of the mapping resolution. This study suggested that GWAS of derivative breeding lines is a credible strategy for improving mapping resolution.