Functionally diverse flax-based rotations improve wild oat (Avena fatua) and cleavers (Galium spurium) management

Wild oat (Avena fatua L.) and false cleavers (Galium spurium) are currently a challenge to manage in less competitive crops such as flax (Linum usitatissimum L.). Increasing the functional diversity in crop rotations can be an option to improve weed management. Nonetheless, this strategy is not tested in flax in Western Canada. A 5-yr (2015-2019) crop rotation study was carried at three locations in western Canada to determine the effect of diverse flax-based crop rotations with differences in crop species, crop life cycles, harvesting time and reduced herbicides on managing A. fatua and G. spurium. The perennial rotation (flax-alfalfa (Medicago sativa L.)-alfalfa-alfalfa-flax) under reduced herbicide use was found to be the most consistent cropping system, providing similar A. fatua and G. spurium control to the conventional annual flax crop rotation[flax-barley (Hordium vulgare L.)-flax-oat (Avena sativa L.)-flax] with standard herbicides. At Carman, this alfalfa rotation provided even better weed control (80% A. fatua, 75% G. spurium) than the conventional rotation. Furthermore, a greater A. fatua control was identified compared to conventional rotation where two consecutive winter cereal crops were grown successfully in rotation (flax-barley-winter triticale (x Triticosecale ex A. Camus)-winter wheat (Triticum aestivum L.)-flax), greater A. fatua control was observed compared to the conventional crop rotation under standard herbicides. Incorporation of silage oat crops did not show consistent management benefits compared to the perennial alfalfa rotation but were generally similar to the conventional rotation with standard herbicides. The results showed that perennial alfalfa in the rotation minimized G. spurium and A. fatua in flax cropping systems, followed by rotations with two consecutive winter cereal crops.

Biochemical and Rapid Molecular Analyses to Identify Glyphosate Resistance in Lolium spp.

Lolium spp. are troublesome weeds mainly found in winter cereal crops worldwide, including Europe. In recent years resistant mechanisms have been evolved to several important herbicides. In this study we investigated the mechanisms responsible for conferring glyphosate resistance in some Lolium spp. populations. A holistic approach was used, based on dose-response experiments, determination of shikimic acid concentration in plant leaf tissue, as well as molecular analyses. More specifically, in three Lolium spp. populations the existence of a mutation in the Pro-106 codon of the 5-enolpyruvylshikimate-3 phosphate synthase (EPSPS) gene was investigated as well as the relative transcript levels of four ABC-transporter genes were monitored at three time points after glyphosate application. The results demonstrated that glyphosate resistance is a multifactor phenomenon. Relative transcript levels of the ABC-transporter genes were abundant at very early time points after glyphosate treatments. Dose-response experiments and shikimate analyses were in accordance with the findings of the quantitative PCR (qPCR) analyses. We suggest that relative expression ratio of ABC-transporter genes can be a useful tool to rapidly identify Lolium spp. populations resistant to glyphosate.

Assessment and modeling of the generation and transport of water and solutes in representative watersheds of Navarre (Spain): toward an optimal and sustainable agrarian activity

The overarching aim of this thesis is to expand the knowledge base on the dynamics of total dissolved solids, with special focus on the most widespread nutrients in agricultural systems (N, and to a lesser extent P). To this end, (1) the exports of dissolved solids and their dynamics in a watershed network have been quantified, considering different agrosystems of the region of Navarre (Spain). Recognizing the influence of these compounds on different water bodies, and with the aim of shedding more light on the black box watershed approach in water quality, (2) the relatively recent concept of overland flow connectivity has been assessed through an Overland Flow Connectivity index. This index is based on broadly adopted overland flow connectivity indices, and implemented at two rainfed winter cereal watersheds (Latxaga and La Tejería). Regarding nutrients, and focusing on nitrate and phosphate dynamics, (3) these two watersheds have been characterized in terms of concentration and exports of nitrate and phosphate, for a range of temporal scales, with insights on the controlling factors of these processes. Finally, (4) the nutrient controlling factors previously identified have been quantified considering different possible scenarios. The AnnAGNPS model capacity has been evaluated for dissolved nitrogen exports at the two rainfed winter cereal watersheds.

Wheat and Cereal Rye Inter-Row Living Mulches Interfere with Early Season Weeds in Soybean

Rapid growth of cool-season weeds in the spring exacerbates weed interference during early soybean (Glycine max (L.) Merr.) establishment in northern climates. This study tested the utility of spring-seeded inter-row living mulches in soybean for early season weed suppression using volunteer canola (Brassica napus L.) as a representative model weed species. The effects of the presence or absence of spring wheat (Triticum aestivum L.) or winter cereal rye (Secale cereale L.) living mulches (mulch type) that had been seeded simultaneously with soybean grown using 38 or 76 cm row spacing (spatial arrangement) and the presence or absence of herbicides used for mid-season mulch termination (herbicide regime) were evaluated in three environments in Manitoba, Canada, in 2013 and 2014. Soybean yield was similar in the presence and absence of the living mulches. In the environment that received the lowest precipitation (Carman 2013), the mulches terminated with post-emergence glyphosate resulted in a 55% greater soybean yield compared to the mulches that remained live throughout the growing season. Inter-row mulches that had been living or terminated mid-season reduced volunteer canola seed production by about one-third (up to 9000 seeds m−2). This study demonstrates the utility of wheat or cereal rye inter-row living mulches for enhanced interference with weeds during early soybean establishment.

Advances in breeding techniques for durable Septoria tritici blotch (STB) resistance in cereals

Septoria tritici blotch (STB), caused by the hemibiotrophic fungus Zymoseptoria tritici, is one of the most important foliar diseases of winter cereal crops. Recent advances are helping to understand the genetic basis and architecture of resistance to STB. To date, at least 22 genes for qualitative resistance and over 200 quantitative trait loci (QTL) for quantitative resistance have been identified in cereals. This knowledge is enabling cereal breeding programs to develop varieties with more durable resistance to STB. This chapter reviews recent research on genetic resistance loci and breeding strategies based on both conventional and biotechnology-based breeding approaches (molecular marker/genomic-assisted breeding, genetic transformation, and gene-editing) to achieve achieving durable resistance to STB infection and minimise grain yield losses.

Tillage and Liquid Dairy Manure Effects on Overland Flow Nitrogen and Phosphorus Loss Potential in an Upper Midwest Corn Silage-Winter Triticale Cropping System

Dairy manure is an important crop nutrient source in Wisconsin and other parts of the upper Midwest but can contribute to nitrogen (N) and phosphorus (P) losses in overland flow/surface runoff. Winter cereal grain cover crops can help reduce erosion and nutrient transport in corn systems. However, few studies have compared tillage impacts on nutrient loss in live cover crop systems. The objective of this study was to evaluate vertical (VT) and chisel tillage (CT) effects on overland flow nutrient and sediment loss potential after spring-applied liquid manure. A surface application treatment (i.e., broadcast) and a no manure control were also included for comparison. After corn (Zea mays L.) planting into a live triticale (Triticale hexaploide L.) cover crop, four artificial rainfall-overland flow events were generated (42 mm h−1 for 30 min) on replicated field-scale plots in central Wisconsin. Mean total P, total N, and suspended solids loads were consistently lower for VT at 2 days post-manure application (with 97 to 99% lower losses than broadcast, respectively). Dissolved reactive P and ammonium-N concentrations for both CT and VT were significantly lower three weeks after manure application compared to broadcast. Results suggest that VT reduced soil/residue disturbance while incorporating manure sufficiently to reduce sediment, N, and P transport potential under simulated high overland flow conditions.

Short communication: A predictive model for the time course of seedling emergence of Phalaris brachystachys (short-spiked canary grass) in wheat fields

Aim of study: A predictive model of the seedling emergence pattern of Phalaris brachystachys Link (short-spiked canary grass) was developed, aimed to contribute to support a more efficient management of this troublesome, competitive weed in winter cereal crops around its native Mediterranean range and in different areas of the world where it is introduced. Area of study: Southern (Andalusia) and northern Spain (Navarra). Material and methods: A model describing the emergence pattern of P. brachystachys in cereal fields based on accumulation of hydrothermal time in soil was developed and validated. For model development, cumulative emergence data were obtained in an experimental field, while an independent validation of the model was conducted with data collected in two commercial wheat fields from climatically contrasting regions of Spain. Main results: The relationship between cumulative emergence and cumulative hydrothermal time (CHT) was well described by a Logistic model. According to model predictions, 50% and 95% seedling emergence takes place at 108 and 160 CHT above base water potential for seed germination, respectively. The model accurately predicted the seedling emergence time course of P. brachystachys in the two commercial wheat fields (R2 ≥ 0.92). Research highlights: This model is a new tool that may be useful to improve the timing of control measures to maximize efficiency in reducing P. brachystachys infestations in cereal crops.

In situ ruminal degradability and fermentation characteristics of novel mixtures of winter cereal and Italian ryegrass plus winter cereal silages

This study was conducted using three multiparous non-lactating rumen-cannulated Holstein-Friesian dairy cows, with the objective of evaluating the in situ ruminal degradability and fermentation characteristics of novel mixtures of winter cereal and Italian ryegrass (Lolium multiflorum Lam.) plus winter cereal silages (mixture A: triticale, oats, barley and wheat; mixture B: triticale, barley and wheat; mixture C: Italian ryegrass and oats; mixture D: Italian ryegrass, oats, triticale, barley and wheat). The rumen fermentation study was conducted replacing the ensiled mixtures (experimental diets) with vetch-triticale haylage in a total mixed ration (control diet). It was found that the effective protein degradability at 0.08 rumen outflow rates was 80.6% (mixture A), 66.2% (mixture B), 79.7% (mixture C) and 79.3% (mixture D). The effective neutral detergent fibre (NDF) and acid detergent fibre (ADF) effective degradability at 0.08 rumen outflow rates was 18.0% and 17.7% (mixture A), 19.7% and 20.5% (mixture B), 19.1% and 17.0% (mixture C), and 15.2% and 14.6% (mixture D), respectively. Different dietary treatments did not change (P > 0.05) the rumen fermentation characteristics as there was no difference (P > 0.05) between control and experimental diets, and the inclusion of 40–55% Italian ryegrass (mixture C and D) did not cause any difference. These results suggest that the mixture of winter cereals and Italian ryegrass plus winter cereal-based silages had good potentially degradable dry matter, effective dry matter and effective protein degradability at 0.01, 0.05 and 0.08 rumen outflow rates without affecting the rumen environment maintaining neutral pH. The ensiled mixtures had a moderate level of potentially degradable NDF and ADF fractions.

Effect of planting into a green winter cereal rye cover crop on growth and development, seedling disease and yield of corn

Terminating winter cereal rye (Secale cereale L.) cover crops (CCs) 10 or more days before planting corn is recommended to minimize seedling disease and potential yield loss. In Iowa, cold temperatures and frequent precipitation can prevent farmers from following that recommendation and sometimes forcing them to plant corn while the rye plants are still green, referred to as planting green (PG). A field trial was established to evaluate the effect of rye termination shortly before or after corn planting on growth, seedling root disease, and yield of corn. A rye CC was terminated 17 and 3 days before planting (DBP), and 6 and 12 days after planting (DAP) corn; corn planted following no rye was included as a control. Rye biomass, C:N ratio, and N accumulation increased when terminated 6 or 12 DAP corn compared with rye terminated 17 or 3 DBP corn. Corn seedlings were taller from the PG treatments. More radicle root rot was observed when rye was terminated 3 DBP, 6 DAP, and 12 DAP corn than for the 17 DBP treatment and the no-rye control. Generally, greater Pythium Clade B populations were detected on radicles and seminal roots of corn from the PG treatments. Corn populations, ears, or barren plants were not affected by the treatments. In both years, the no-rye control had the greatest corn yield and the 12 DAP treatment had the lowest yield. Our results suggest that PG increased corn seedling root disease and contributed to reduced corn yield.