Variety Mixtures Research Articles

The Management of Fungal Diseases in Organic Production Systems Through a Mixture of Durum Wheat Varieties

Fungal diseases are a yield-limiting factor for wheat. Their management in organic production systems is one of the prevailing challenges because it must be based mainly on indirect measures through agricultural practices. Variety mixtures are one of these practices, a concept that has been demonstrated to improve several factors affecting yield. Recently, it has become a practice that enables sustainability in agriculture. Our research aim is to evaluate the capacity of this practice to control three fungal diseases (foliar and ear) on durum wheat. This study was conducted over two consecutive years (2019 and 2020) at two locations: a certified organic farm in the Benslimane region (2019) and the National School of Agriculture farm in Meknes (2020). Four durum wheat varieties (Isly, Tarek, Karim, and Nassira) were used to create the mixture. The parameters that were monitored were the disease severity, the grain yield, and its components. The analysis of variance for the three fungal diseases’ severity was significant. The variety that showed resistance to all diseases was the Isly variety, and the most susceptible variety was the Nassira variety. The resistance of the other varieties to the diseases was variable from one year to the other. The mixture showed average severity values. It allowed a reduction in the severity of leaf rust of 47% during the first year and 30% during the second year compared to the most susceptible variety (Nassira). In the case of HLB (helminthosporiosis leaf blight), it reduced the disease by 47% during the first year and 34% during the 2020 season. For ear disease, Fusarium head blight (FHB), the reduction was 68% during the year 2019 and 49% during 2020. The mixture also ensured yield stability between the two trial years (1.66 t ha−1 and 1.54 t ha−1).

Hotspot detection in the cultivation of organic winter wheat variety mixtures

Hotspot detection in the cultivation of organic winter wheat variety mixtures

Evaluation of biomass yield and seed yield of vetch and oats variety mixtures

Evaluation of biomass yield and seed yield of vetch and oats variety mixtures

Cropping Systems Diversification as an Approach to Enhancing Crop Productivity: A Review

Agricultural intensification increased crop productivity but simplified production with lower diversity of cropping systems, higher genetic uniformity, and a higher uniformity of agricultural landscapes. Associated detrimental effects on the environment and biodiversity as well as the resilience and adaptability of cropping systems to climate change are of growing concern. Crop diversification may stabilize productivity of cropping systems and reduce negative environmental impacts and loss of biodiversity, but a shared understanding of crop diversification including approaches towards a more systematic research is lacking. The current review highlights the use of Cropping Systems Diversification as an Approach to Enhancing Crop Productivity. Crop diversification can be considered as an attempt to increase the diversity of crops through, e.g. crop rotation, multiple cropping or intercropping, compared to specialized farming with the aim to improve the productivity, stability and delivery of ecosystem services. It can be one measure to develop more sustainable production systems, develop value-chains for minor crops. Crop diversification practices can include higher crop diversity, more diverse crop, mixed cropping; cultivation of grain legumes in otherwise cereal dominated systems, perennial leys or grassland and regionally adapted varieties or variety mixtures. Crop diversification and/or additional diversification measures like variation of seeding time or changing cropping patterns have the potential to lead to higher and more stable yields, increase profitability and lead to greater resilience of agro-ecosystems in the long term. These practices have the potential to make cropping systems more diverse in space, time and genetics. Through a balanced portfolio approach to agricultural sustainability, cropping system performance can be optimized in multiple dimensions, including food and biomass production, profit, energy use, pest management, and environmental impacts.

Mix and manage: Cultivar mixtures can maintain yield under high wheat blast disease pressure

Originating in South America, wheat blast disease has spread to both Asia and Africa and is considered a significant threat to food security. Bangladesh experienced the first outbreak of wheat blast outside of the Americas in 2016. Shortly thereafter, the blast-resistant variety BARI Gom 33 was released. Seeds of this variety are however not as widely available as required, although the disease threat remains. While varietal mixtures have been shown to mitigate some symptoms and yield losses associated with other fungal diseases in wheat, there is a complete research gap on this topic as it pertains to wheat blast. As such, we evaluated the potential of using BARI Gom 33 as a component of a variety mixture under high disease pressure in Bangladesh. During three cropping seasons, blast symptoms and yield were determined in a field experiment for the highly blast-susceptible variety BARI Gom 26, the moderately susceptible BARI Gom 30, the resistant BARI Gom 33, and seven mixture combinations of the three varieties using artificial inoculation to increase disease pressure. In addition to wheat blast, Bipolaris leaf blight (BpLB) symptoms were observed and evaluated. While yields of the susceptible varieties were severely affected by blast even after fungicide application, disease-inflicted yield loss without fungicide was only 15% for sole BARI Gom 33 and did not differ significantly from yield losses in BARI Gom 33 and BARI Gom 30 mixtures. Furthermore, in the mixture containing 67% BARI Gom 33 and 33% BARI Gom 30, blast incidence and severity were reduced by 25% and 16%, respectively, in comparison to weighted values in sole stands. Conversely, mixing varieties tended to increase the symptoms of BpLB. Under high wheat blast pressure, fungicide protection against blast was relatively weak, underscoring the importance of resistant varieties. Although variety mixtures did not increase yield, the yield advantage of BARI Gom 33 was maintained when its seeds were mixed with the less resistant BARI Gom 30. This study confirms recommendations that farmers should use BARI Gom 33 as a first line of defense against wheat blast in Bangladesh. Yet where farmers cannot access sufficient BARI Gom 33 seed for planting, our data suggest that agricultural extension services can recommend this variety with non-resistant cultivars as interim strategy without significant risk of yield loss.

Management of Rust in Wheat Using IPM Principles and Alternative Products

Overall, there is a major wish that European farmers implement integrated pest management (IPM), particularly to reduce dependence on pesticides. In the European Rustwatch project, partners conducted nineteen trials across nine different countries during 2020 and 2021 to investigate different IPM strategies, focusing on controlling rust diseases in winter wheat. The trials included the use of varieties with contrasting levels of resistance, variety mixtures, reduced fungicide rates, thresholds, and Decision Support Systems (DSSs), and testing alternative products to fungicides. Sixteen trials developed yellow rust (Puccinia striiformis f. sp. tritici) infections, and six trials developed brown rust (Puccinia triticina) infections. Resistant varieties proved highly effective in keeping down yellow rust infection, and variety mixtures also effectively reduced infection levels and stabilized yields. Rust was fully controlled using 25% of standard fungicide rates, even under high disease pressure. Using DSSs provided sufficient control of rust diseases and resulted in competitive net economic returns due to fewer fungicide applications. The alternative products tested included two biological control agents and four alternative chemistries, which all gave inferior and insufficient control against rust compared with chemical fungicides. The trial work demonstrated that there are good and reliable options for including IPM into disease control in wheat.

Baking quality of wheat variety mixtures: Describing the mechanisms for mixture effects

The use of intra-crop diversity (e.g.: variety mixtures) in bread wheat cropping is getting popular in Europe, mostly for agronomic purposes. However, much less is known about the implications on baking quality.In this paper, we formalized and tested a framework based on two hypothetical mechanisms for mixture effects as a result of plant interactions within mixtures: (i) proportion shifts, relating to changes in grain weight proportion of the varieties at harvest and (ii) component alteration, relating to changes in the baking quality of the component varieties. To test this framework, we measured several baking quality indicators on twelve variety mixtures and their component varieties in pure stands. By recording varietal proportions at harvest, we could measure the relative importance of both mechanisms in explaining observed mixture effects.Our results showed that proportion shifts explained a large share of mixture effects on protein baking quality (Zélény sedimentation index and W baking strength) but failed to explain mixture effects on protein content in one year and Hagberg's falling number in both years. Our results also suggest component alteration on protein content resulting from altered nitrogen uptake in mixtures, and possibly on Hagberg's falling number resulting from lodging reduction in mixtures.

Haitian coffee agroforestry systems harbor complex arabica variety mixtures and under-recognized genetic diversity.

Though facing significant challenges, coffee (Coffea arabica) grown in Haitian agroforestry systems are important contributors to rural livelihoods and provide several ecosystem services. However, little is known about their genetic diversity and the variety mixtures used. In light of this, there is a need to characterize Haitian coffee diversity to help inform revitalization of this sector. We sampled 28 diverse farms in historically important coffee growing regions of northern and southern Haiti. We performed KASP-genotyping of SNP markers and HiPlex multiplex amplicon sequencing for haplotype calling on our samples, as well as several Ethiopian and commercial accessions from international collections. This allowed us to assign Haitian samples to varietal groups. Our analyses revealed considerable genetic diversity in Haitian farms, higher in fact than many farmers realized. Notably, genetic structure analyses revealed the presence of clusters related to Typica, Bourbon, and Catimor groups, another group that was not represented in our reference accession panel, and several admixed individuals. Across the study areas, we found both mixed-variety farms and monovarietal farms with the historical and traditional Typica variety. This study is, to our knowledge, the first to genetically characterize Haitian C. arabica variety mixtures, and report the limited cultivation of C. canephora (Robusta coffee) in the study area. Our results show that some coffee farms are repositories of historical, widely-abandoned varieties while others are generators of new diversity through genetic mixing.

Olive trees in the world. Past and present with future perspectives

The cultivation of the olive tree is of great economic importance worldwide. For the 2022-2023 harvest, were produced around 3,010,000 Mg of olive oil and 2,955,500 Mg of table olives of selected varieties, managing to establish itself in approximately 56 countries with different environments. In most of the cultivated areas only monovarietals were used, but mixtures of varieties have been recommended, which act as pollinators, avoiding reproduction problems. Furthermore, global warming also affects production efficiency and the quality of derived products. The olive grove underwent important changes due to genetic improvement. However, despite modern molecular tools, most of the work continues to be based on agronomic classical methods such as crossing and selection in progeny, delaying the development of new varieties. Models with high resolution climate projections are being used, allowing predicting the future evolution of the olive tree. Unfortunately, Brazil produces only 0.2% of its internal consumption and therefore has become the world's second largest importer after the United States to cover the growing demand. Based on this information, this review aims to discuss the adjustments in olive growing, which has been gaining more and more areas dedicated to its cultivation in Brazil.

Erratum to: Mixing things up! Identifying early diversity benefits and facilitating the development of improved variety mixtures with high throughput field phenotyping

Erratum to: Mixing things up! Identifying early diversity benefits and facilitating the development of improved variety mixtures with high throughput field phenotyping

Variety mixtures of winter wheat: a general status and national case study

Food and feed production worldwide heavily relies on wheat (Triticum aestivum). However, current agricultural practices face numerous challenges including a shortage of land for cultivation, a desire to reduce the use of chemical pesticides and fertilizers, and the development of resistance towards employed pesticides and virulence towards host resistance in the most widely grown varieties. In this paper, we demonstrate based on the literature that cultivating wheat variety mixtures generally leads to increased yield and yield stability across years and environments, reduced severity of multiple diseases, and a decreased risk of lodging before harvest compared to the cultivation of pure stands. Moreover, mixtures may delay fungicide resistance development and increase genetic diversity, ultimately prolonging the durability of resistance genes. Furthermore, growing mixtures may lower the risk of crop failure due to more extreme weather events and lead to better utilization of water and nutrients. We discuss a Danish case study advocating the cropping of wheat varieties in mixtures as an example of how variety mixtures can be utilized in integrated pest management strategies. The study shows that if all involved stakeholder groups promote the adoption of variety mixtures, a major uptake by farmers can be reached, potentially reducing the dependency on pesticides in current cropping schemes.

Asynchrony is more important than genetic distance in driving yield stability in wheat variety mixtures

AbstractIn the face of climate change, improving yield stability is critical for food production systems. Increasing diversity in agricultural systems can be a way to stabilize yield across time and/or space. This can be done with mixtures of varieties, which represent a practical way to introduce diversity at the genotype level in agricultural fields. However, in Switzerland, wheat variety mixtures are still rarely used, due to a lack of understanding of the processes driving yield benefits and, consequently, no clear rules as to which varieties to combine. In this study, we used results from a Swiss wheat variety mixture trial to investigate the drivers of mixture productivity and stability. We hypothesized that mixtures composed of more different varieties—in terms of genetic distance but also of morphological, agronomic, or synchronicity aspects—would be more productive and/or stable. We did not find any effects of genetic distance on mixture productivity or stability, but we did observe an increase in mixture stability with reduced synchrony of the components, that is, when the components reacted differently to environmental conditions. This result was only significant in the first year of the trial, which was less productive due to more stressful conditions. This study shows that when combining asynchronous varieties, wheat variety mixtures have the potential to buffer possible yield losses due to external stressors during suboptimal years. While more research is needed to confirm this result, variety mixtures nonetheless represent a promising solution to sustainably increase the stability of wheat production in Switzerland.

Mixing things up! Identifying early diversity benefits and facilitating the development of improved variety mixtures with high throughput field phenotyping

AbstractCrop diversification is a potential strategy to increase the stability and productivity of crops, while reducing pathogen pressures and pesticide requirements. Crop variety mixtures provide some of these diversification benefits and their cultivation is fully compatible with current mechanized agronomic practices. However, the development of optimal variety mixtures is a long, labour‐intense process requiring extensive field trials. High throughput field phenotyping (HTFP) methods provide promising applications in field testing because they allow for precise, repeatable, and rapid measurements of crop properties. Here, we evaluated the use of HTFP for developing high‐performing oat (Avena sativa) variety mixtures by testing its suitability to predict diversity yield benefits from repeated canopy measurements across the growing season. Analyzing 26 mixtures of five varieties, we found significant overyielding at harvest, that is, mixtures were on average more productive than expected based on component pure stands. This grain yield overyielding was well predicted from deviations between mixture and pure stand canopy cover estimations, derived from HTFP mid‐way through the growing season. This shows that (i) positive interactions between oat varieties occur already at an early stage, (ii) such interactions lead to increased potential for light interception, (iii) HTFP offers rapid, scalable methods to screen for performant variety mixtures.

An Analysis of Language Variation in Banjar Puaya: A Sociolinguistic Study

Language and society have strong relations on each other in which they interfere on any aspect in a language. Social interaction can emerge large variety of languages because the speakers may produce new languages more and have more choices in using the language. This case can be referred to language varieties that occur within a social interaction. This study was aimed to analyze the language variations in Banjar Puaya communities. The research used a qualitative method with a case study to explain the phenomenon found in the field. The data analysis was done by observing and interviewing youth and adult communities of Banjar Puaya. The result found some classifications of language variations namely dialects, registers, mixtures of varieties, and secret language variations. The variation occurred based on the environment and situation and condition's influence. Therefore, it is possible that language can still be modified and developed since the society makes any variation in the use of language.

Increasing intraspecific diversity of wheat affects plant nutrient contents but not N recovery in the plant-soil system

Crop homogenization in conventional agriculture has been pervasive while ecology has shown positive effects of biodiversity on ecosystem functioning, that arise from complementarity/facilitation and sampling/selection effects. These effects are well documented for interspecific diversity in both natural ecosystems and agroecosystems but remain less documented at an intraspecific level, particularly for the rates of nutrient uptake by plants and nutrient losses from ecosystems. We conducted a field experiment with 88 experimental plots cultivated with 1, 2, 4 or 8 wheat varieties and 1, 2, 3 or 4 functional groups to assess the effects of the number of varietal and functional diversity of winter wheat on plant biomass production, plant nutrient contents (N, Ca, Cu, Fe, Mg, Mn, P, K, Na and Zn) and fertilizer N recovery in the plant-soil system using a 15N labeling method. We found both negative and positive effects of the number of varieties or number of functional groups on shoot Cu, Fe, Zn, Na and P contents, but no significant effects of intraspecific diversity on biomass production, N content and 15N recovery in the plant-soil system. Our results show differential responses to an increase of intraspecific diversity of wheat on the contents of several essential nutrients in plants and highlight the need to jointly analyze multiple nutrients. Our study also suggests that increasing intraspecific diversity had no overall negative effects on biomass production or N content. Using knowledge on variety functional traits to target specific complementarity mechanisms when designing variety mixtures could thus lead to a positive effect on nutrient absorption and biomass production.

Unfolding the link between multiple ecosystem services and bundles of functional traits to design multifunctional crop variety mixtures

In face of the current environmental challenges, developing multifunctional cropping systems is increasingly needed, and crop variety mixtures are particularly interesting since they can deliver diverse services including grain production, yield stability, N2O production regulation, disease control, and reduction of N-fertilizer losses. However, the relationships between intraspecific diversity and ecosystem multifunctionality are poorly understood so far, and practitioners lack science-based guidance to design mixtures. We used a pool of 16 bread wheat varieties classified into 4 functional groups based on 26 below- and aboveground functional traits, to conduct a field trial (88 large plots cultivated with single varieties or mixtures of 2, 4, or 8 varieties), quantifying 15 provisioning and regulating services for each plot. To assess yield stability between local conditions and years, the trial was replicated at 4 other locations and for 2 years, using 2 managements each time. We analyzed how variety number and functional groups predicted the variance in services, and applied in an innovative manner the RLQ co-inertia analysis to relate the (variety × traits) matrix Q to a (plot × services) matrix R, using a (plot × variety) composition matrix L as a link. Our results show that using variety mixtures allowed delivery of baskets of services not reachable when cultivating single varieties, and that mixtures mitigated tradeoffs between different pairs of services. Variety number or functional groups poorly predicted the variance in services, but the RLQ approach allowed the identification of groups of plots delivering consistent baskets of services. Moreover, we demonstrated for the first-time significant relationships between specific baskets of services and bundles of variety traits. We discuss how our results increase our understanding of intraspecific diversity–agroecosystem multifunctionality relationships, and propose the next steps using our new approach to support practitioners for designing variety mixtures that provide particular baskets of services.

Single-gene resolution of diversity-driven overyielding in plant genotype mixtures

In plant communities, diversity often increases productivity and functioning, but the specific underlying drivers are difficult to identify. Most ecological theories attribute positive diversity effects to complementary niches occupied by different species or genotypes. However, the specific nature of niche complementarity often remains unclear, including how it is expressed in terms of trait differences between plants. Here, we use a gene-centred approach to study positive diversity effects in mixtures of natural Arabidopsis thaliana genotypes. Using two orthogonal genetic mapping approaches, we find that between-plant allelic differences at the AtSUC8 locus are strongly associated with mixture overyielding. AtSUC8 encodes a proton-sucrose symporter and is expressed in root tissues. Genetic variation in AtSUC8 affects the biochemical activities of protein variants and natural variation at this locus is associated with different sensitivities of root growth to changes in substrate pH. We thus speculate that - in the particular case studied here - evolutionary divergence along an edaphic gradient resulted in the niche complementarity between genotypes that now drives overyielding in mixtures. Identifying genes important for ecosystem functioning may ultimately allow linking ecological processes to evolutionary drivers, help identify traits underlying positive diversity effects, and facilitate the development of high-performance crop variety mixtures.

Ecological principles to guide the development of crop variety mixtures

AbstractCrop variety mixtures can provide many benefits, including pathogen suppression and increased yield and yield stability. However, these benefits do not necessarily occur in all mixtures, and the benefits of diversity may be compromised by disadvantages due to increased crop heterogeneity. In-field development of mixtures by assembling many combinations of crop genotypes without prior expectation about which genotypes need to be combined to produce well-performing mixtures results in prohibitively large designs. Therefore, effective tools are required to narrow down the number of promising variety mixtures, and to then identify in experiments which of these deliver the highest benefits. Here, we first review current knowledge about the mechanisms underlying effects in ecological diversity experiments and in current agricultural applications. We then discuss some of the principal difficulties arising in the application of this knowledge to develop good variety mixtures. We also discuss non-conventional approaches to solve some of these issues. In particular, we highlight the potential and limitations of trait-based methods to determine good variety mixing partners, and argue that nontraditional traits and trait-derived metrics may be needed for the trait-based approach to deliver its full potential. Specifically, we argue that good mixing partners can be identified using modern genetic and genomic approaches. Alternatively, good mixtures may be obtained by combining varieties that respond differently to environmental variation; such varieties could easily be identified in standard variety testing trials. Preliminary analyses show that niche differences underlying the different environmental responses can indicate functional complementarity and promote mixture yield and yield stability.

Smallholder Farmers’ Coping Strategies to Perceived Climate Change and Variability in Isingiro District, South Western Uganda

Climate change and variability pose a major challenge facing the agricultural sector around the world and trends are feared to intensify by 2050. This is likely to complicate agricultural decisions affecting local communities who depend on the sector for their livelihood. Seasonal changes in weather patterns are projected to reduce food production due to the reduction in average yields of common food crops. With the majority of smallholder farmers in Uganda depending on agriculture for survival, building their adaptive capacity to climate change is vital to ensure household food and income security. This study aimed at establishing the smallholder farmers’ perceptions of climate change and their initiatives to cope with and manage the associated risks. A sample of 126 farming households were randomly selected from three Sub counties in Isingiro District and studied using field observations and questionnaires. Key informant interviews were also conducted with three extension workers. The collected data was analysed using Stata 14 and Excel. The findings revealed that there was increasing awareness of the climate change and variability challenge among smallholder farmers with the increasing need to take on adaptation strategies. The results showed that the major perceived changes were, increased intensity and frequency of droughts (98%), increase in daytime temperatures (92.7%), decrease in rainfall intensity (92.1%) and changes in rainfall distribution patterns (90%). It also showed that different initiatives had been taken by farmers to cope with the changes like changing planting dates (92.1%), growing crop variety mixtures (73.8%) and practising soil and water conservation (62.7%). Based on the findings of this study, smallholder farmers greatly perceived climate change and variability with negative impacts imposed on their farming operations. Although farmers have tried to adapt, there is still a need to support their coping strategies through appropriate policies. This will facilitate increased adoption of adaptation measures, thereby reducing the negative consequences of climate change in future

WINTER WHEAT MIXTURES INFLUENCE GRAIN RHEOLOGICAL AND MIXOLAB QUALITY

This study aims to investigate the effect of a mixture of winter wheat varieties on grain rheological characteristics and the quality of wheat flour analyzed by Mixolab. In the 2019-2020 growing season, a small plots experiment was carried out in an organically certified field in the Czech Republic. The experiment was conducted by randomized complete block design with three replicates, four winter wheat (Triticum aestivum L.) varieties with four mixtures of the same varieties in equal proportions. Based on the results, the expected grain yield was not achieved. The quality of wheat productivity was significantly different among treatments in terms of protein content, wet gluten, sedimentation value, and falling number (P < 0.001). Protein content ranged between 8.04% and 9.85%, mixtures of Butterfly + Lorien and Illusion + Lorien were higher in protein than Illusion and Vanessa varieties and their combination. The highest wet gluten was found under mixtures of Butterfly + Lorien varieties (19.34%) while sowing Butterfly variety gave the highest Zeleny test and falling number compared to other treatments. Butterfly + Lorien and Butterfly + Vanessa mixtures obtained good results for falling number at 250.67 and 272.67 seconds. There were significant differences in rheological quality parameters of winter wheat varieties analyzed by Mixolab including stability, weakening of protein, and starch (P < 0.01 and P < 0.001, except slope gamma). Although the observed benefits were limited to grain yield, mixtures of individual cultivars appear to be a potential tool to improve overall crop performance (grain quality).