Effects of long-term different-scale rice-duck farming on the growth and yield of paddy rice

BACKGROUND

To maintain rice production and increase revenue, rice-duck (RD) farming is a contemporary ecological cycle technology that has been widely used in Asia. However, due to the clustering activity of duck flocks, the consequences of long-term RD farming on rice growth at different scales are still unknown. Here, we studied RD farming using several different treatments (CK: conventional rice farming; RD1: 667 m2 ; RD2: 2000 m2 ; and RD3: 3333 m2 ).

RESULTS

The results demonstrated that the maximum tillers, effective spikes, dry matter accumulation, and lodging index of rice under RD farming were significantly decreased by 17.9%, 9.8%, 14.8%, and 17.8%, respectively, which ultimately caused a significant decrease in yield of 10.6%. However, RD farming significantly increased root oxidation activity and the ear-bearing tiller rate of rice by 25.5% and 11.1%, respectively, and improved yield stability. For different scales of RD farming, the lodging resistance index of RD1 was significantly lower than that of RD2 and RD3 by 10.0% and 15.2%, respectively, whereas the root oxidation activity and dry matter accumulation of RD2 were significantly higher than those of RD1 and RD3 by 11.1%, 4.7%, 8.6%, and 5.1%, respectively. For rice yield, there was no significant difference among the different scales.

CONCLUSION

This long-term experiment helped elucidate the complicated effects of RD farming at different scales on the growth and yield of rice. It is also critical to consider the economic advantages of different scales of RD farming to assess the impact of this system more thoroughly. © 2023 Society of Chemical Industry.

Exploring the Drought Tolerant Quantitative Trait Loci in Spring Wheat

Drought-induced stress poses a significant challenge to wheat throughout its growth, underscoring the importance of identifying drought-stable quantitative trait loci (QTLs) for enhancing grain yield. Here, we evaluated 18 yield-related agronomic and physiological traits, along with their drought tolerance indices, in a recombinant inbred line population derived from the XC7 × XC21 cross. These evaluations were conducted under both non-stress and drought-stress conditions. Drought stress significantly reduced grain weight per spike and grain yield per plot. Genotyping the recombinant inbred line population using the wheat 90K single nucleotide polymorphism array resulted in the identification of 131 QTLs associated with the 18 traits. Drought stress also exerted negative impacts on grain formation and filling, directly leading to reductions in grain weight per spike and grain yield per plot. Among the identified QTLs, 43 were specifically associated with drought tolerance across the 18 traits, with 6 showing direct linkages to drought tolerance in wheat. These results provide valuable insights into the genetic mechanisms governing wheat growth and development, as well as the traits contributing to the drought tolerance index. Moreover, they serve as a theoretical foundation for the development of new wheat cultivars having exceptional drought tolerance and high yield potentials under both drought-prone and drought-free conditions.

Genomic regions of durum wheat involved in water productivity

Durum wheat is a staple food in the Mediterranean Basin, mostly cultivated under rainfed conditions. As such, the crop is often exposed to moisture stress. Therefore, the identification of genetic factors controlling the capacity of genotypes to convert moisture into grain yield (i.e., water productivity) is quintessential to stabilize production despite climatic variations. A global panel of 384 accessions was tested across 18 Mediterranean environments (in Morocco, Lebanon, and Jordan) representing a vast range of moisture levels. The accessions were assigned to water responsiveness classes, with genotypes 'Responsive to Low Moisture' reaching an average +1.5 kg ha-1 mm-1 yield advantage. Genome wide association studies revealed that six loci explained most of this variation. A second validation panel tested under moisture stress confirmed that carrying the positive allele at three loci on chromosomes 1B, 2A, and 7B generated an average water productivity gain of +2.2 kg ha-1 mm-1. These three loci were tagged by kompetitive allele specific PCR (KASP) markers, and these were used to screen a third independent validation panel composed of elites tested across moisture stressed sites. The three KASP combined predicted up to 10% of the variation for grain yield at 60% accuracy. These loci are now ready for molecular pyramiding and transfer across cultivars to improve the moisture conversion of durum wheat.

Exploring Genetics by Environment Interactions in Some Rice Genotypes across Varied Environmental Conditions

Rice production faces challenges related to diverse climate change processes. Heat stress combined with low humidity, water scarcity, and salinity are the foremost threats in its cultivation. The present investigation aimed at identifying the most resilient rice genotypes with yield stability to cope with the current waves of climate change. A total of 34 rice genotypes were exposed to multilocation trials. These locations had different environmental conditions, mainly normal, heat stress with low humidity, and salinity-affected soils. The genotypes were assessed for their yield stability under these conditions. The newly developed metan package of R-studio was employed to perform additive main effects and multiplicative interactions modelling and genotype-by-environment modelling. The results indicated that there were highly significant differences among the tested genotypes and environments. The main effects of the environments accounted for the largest portion of the total yield sum of squared deviations, while different sets of genotypes showed good performance in different environments. AMMI1 and GGE biplots confirmed that Giza179 was the highest-yielding genotype, whereas Giza178 was considered the most-adopted and highest-yielding genotype across environments. These findings were further confirmed by the which-won-where analysis, which explained that Giza178 has the greatest adaptability to the different climatic conditions under study. While Giza179 was the best under normal environments, N22 recorded the uppermost values under heat stress coupled with low humidity, and GZ1968-S-5-4 manifested superior performance regarding salinity-affected soils. Giza 177 was implicated regarding harsh environments. The mean vs. stability-based rankings indicated that the highest-ranked genotypes were Giza179 > Giza178 > IET1444 > IR65600-77 > GZ1968-S-5-4 > N22 > IR11L236 > IR12G3213. Among them, Giza178, IR65600-77, and IR12G3213 were the most stable genotypes. Furthermore, these results were confirmed by cluster-analysis-based stability indices. A significant and positive correlation was detected between the overall yield under all the environments with panicle length, number of panicles per plant, and thousand grain weight. Our study sheds light on the notion that the Indica/Japonica and Indica types have greater stability potential over the Japonica ones, as well as the potential utilization of genotypes with wide adaptability, stability, and high yield, such as Giza178, in the breeding programs for climate change resilience in rice.

Drought response of water-conserving and non-conserving spring barley cultivars

Introduction

Breeding barley cultivars adapted to drought requires in-depth knowledge on physiological drought responses.

Methods

We used a high-throughput functional phenotyping platform to examine the response of four high-yielding European spring barley cultivars to a standardized drought treatment imposed around flowering.

Results

Cv. Chanell showed a non-conserving water-use behavior with high transpiration and maximum productivity under well-watered conditions but rapid transpiration decrease under drought. The poor recovery upon re-irrigation translated to large yield losses. Cv. Baronesse showed the most water-conserving behavior, with the lowest pre-drought transpiration and the most gradual transpiration reduction under drought. Its good recovery (resilience) prevented large yield losses. Cv. Formula was less conserving than cv. Baronesse and produced low yet stable yields. Cv. RGT's dynamic water use with high transpiration under ample water supply and moderate transpiration decrease under drought combined with high resilience secured the highest and most stable yields.

Discussion

Such a dynamic water-use behavior combined with higher drought resilience and favorable root traits could potentially create an ideotype for intermediate drought. Prospective studies will examine these results in field experiments and will use the newly gained understanding on water use in barley to improve process descriptions in crop simulation models to support crop model-aided ideotype design.

An exotic allele of barley EARLY FLOWERING 3 contributes to developmental plasticity at elevated temperatures

Increase in ambient temperatures caused by climate change affects various morphological and developmental traits of plants, threatening crop yield stability. In the model plant Arabidopsis thaliana, EARLY FLOWERING 3 (ELF3) plays prominent roles in temperature sensing and thermomorphogenesis signal transduction. However, how crop species respond to elevated temperatures is poorly understood. Here, we show that the barley ortholog of AtELF3 interacts with high temperature to control growth and development. We used heterogeneous inbred family (HIF) pairs generated from a segregating mapping population and systematically studied the role of exotic ELF3 variants in barley temperature responses. An exotic ELF3 allele of Syrian origin promoted elongation growth in barley at elevated temperatures, whereas plant area and estimated biomass were drastically reduced, resulting in an open canopy architecture. The same allele accelerated inflorescence development at high temperature, which correlated with early transcriptional induction of MADS-box floral identity genes BM3 and BM8. Consequently, barley plants carrying the exotic ELF3 allele displayed stable total grain number at elevated temperatures. Our findings therefore demonstrate that exotic ELF3 variants can contribute to phenotypic and developmental acclimation to elevated temperatures, providing a stimulus for breeding of climate-resilient crops.

Do We Need to Breed for Regional Adaptation in Soybean?-Evaluation of Genotype-by-Location Interaction and Trait Stability of Soybean in Germany

Soybean is a crop in high demand, in particular as a crucial source of plant protein. As a short-day plant, soybean is sensitive to the latitude of the growing site. Consequently, varieties that are well adapted to higher latitudes are required to expand the cultivation. In this study, we employed 50 soybean genotypes to perform a multi-location trial at seven locations across Germany in 2021. Two environmental target regions were determined following the latitude of the locations. Adaptation and trait stability of seed yield and protein content across all locations were evaluated using Genotype plus Genotype-by-Environment (GGE) biplots and Shukla's stability variance. We found a moderate level of crossing-over type genotype-by-location interaction across all locations. Within the environmental target regions, the genotype-by-location interaction could be minimised. Despite the positive correlation (R = 0.59) of seed yield between the environmental target regions and the same best-performing genotype, the genotype rankings differed in part substantially. In conclusion, we found that soybean can be grown at a wide range of latitudes across Germany. However, the performance of genotypes differed between the northern and southern locations, with an 18.8% higher mean yield in the south. This in combination with the observed rank changes of high-performing genotypes between both environmental target regions suggests that selection targeted towards environments in northern Germany could improve soybean breeding for those higher latitude regions.

Optimal Contribution Selection Improves the Rate of Genetic Gain in Grain Yield and Yield Stability in Spring Canola in Australia and Canada

Crop breeding must achieve higher rates of genetic gain in grain yield (GY) and yield stability to meet future food demands in a changing climate. Optimal contributions selection (OCS) based on an index of key economic traits should increase the rate of genetic gain while minimising population inbreeding. Here we apply OCS in a global spring oilseed rape (canola) breeding program during three cycles of S_0,1 family selection in 2016, 2018, and 2020, with several field trials per cycle in Australia and Canada. Economic weights in the index promoted high GY, seed oil, protein in meal, and Phoma stem canker (blackleg) disease resistance while maintaining plant height, flowering time, oleic acid, and seed size and decreasing glucosinolate content. After factor analytic modelling of the genotype-by-environment interaction for the additive effects, the linear rate of genetic gain in GY across cycles was 0.059 or 0.087 t ha^-1 y^-1 (2.9% or 4.3% y^-1) based on genotype scores for the first factor (f₁) expressed in trait units or average predicted breeding values across environments, respectively. Both GY and yield stability, defined as the root-mean-square deviation from the regression line associated with f₁, were predicted to improve in the next cycle with a low achieved mean parental coancestry (0.087). These methods achieved rapid genetic gain in GY and other traits and are predicted to improve yield stability across global spring canola environments.

Abscisic acid and its role in the modulation of plant growth, development, and yield stability

Abscisic acid (ABA) is known to confer stress tolerance; however, at elevated levels it impairs plant growth under prolonged stress. Paradoxically, at its basal level, ABA plays many vital roles in promoting plant growth and development, including modulation of tillering, flowering, and seed development, as well as seed maturation. In this review, we provide insight into novel discoveries of ABA fluxes, ABA signaling responses, and their impact on yield stability. We discuss ABA homeostasis implicated under pre- and postanthesis drought and its impact on productive tillers, grain number determination, and seed development to address yield stability in cereal crops while considering the new knowledge that emerged from the model plant systems.

Effects of agronomic traits and climatic factors on yield and yield stability of summer maize (Zea mays L) in the Huang-Huai-Hai Plain in China

Zhengdan 958 (ZD958) is the summer maize variety with the widest planting area in Huang-Huai-Hai plain in the past 20 years. Understanding the agronomic characteristics of maize and its adaptability to climatic factors is of great significance for breeding maize varieties with high yield and stability. In this study, the experimental data of 33 experimental stations from 2005 to 2015 were analyzed to clarify the effects of different agronomic traits on yield and the correlation between agronomic traits, and to understand the effects of different climatic factors on summer maize yield and agronomic traits. The results showed that the average yield of ZD958 was 9.20 t ha^-1, and the yield variation coefficient was 13.41%. There was a certainly negative correlation between high yield and high stability. Plant heights, ear heights, double ear rate, ear length, ear rows, line grain number, grain number per ear, ear diameter, cob diameter, and 1000 grains weight were significantly positive correlation with maize yield. Solar radiation before and after silking were significantly positive correlation with maize yield. Path analysis showed that changes in agronomic traits accounted for 54% of the yield variation, and changes in climate factors accounted for 26% of the yield variation. Our study showed that higher plant height, ear height, grain number per ear and 1000-grain weight, lower lodging rate, pour the discount rate and shorter bald tip long were the main reasons for high yield. Among the climatic factors, solar radiation and the lowest temperature have significant effects on the yield.

Coffee Yield Stability as a Factor of Food Security

Yield fluctuation is a major risk in all agricultural sectors, and it influences Goal 2 (food security) of the UN SDGs. Yield fluctuations are expected due to climate change, risking stable coffee supplies, and compromising coffee-exporting countries' ability to earn revenue to pay for food imports. Technology minimizing yield fluctuations is crucial for food security and for coffee farmers to earn a stable income. Fluctuations are small if yields remain close to the mean yield trends. In this study, the coffee yields of major producers are analyzed, together with zonal temperature data, to see where coffee is grown with stable technology under rising temperatures; thus, we demonstrate the advantages of the Yield Stability Index (YSI) over traditional stability measurements in guiding policy formulation and managerial decisions. The Yield Stability Index (YSI) is applied for 1961-1994 and 1995-2020, for the world's 12 major coffee-producing countries. The YSI indicates that of the 12 countries, only Indonesia, Honduras, and Mexico maintain stable yield levels, while Brazil and Vietnam considerably improve their yield stability, which traditional stability measures cannot grasp. Country-wise differences exist in environmental vulnerability and adaptability, with implications for food security. The novelty is the application of the YSI, and the connection between yield stability, climate change, and food security.

Comparative Plasticity Responses of Stable Isotopes of Carbon (δ13C) and Nitrogen (δ15N), Ion Homeostasis and Yield Attributes in Barley Exposed to Saline Environment

Salinity is a major threat to agricultural productivity worldwide. The selection and evaluation of crop varieties that can tolerate salt stress are the main components for the rehabilitation of salt-degraded marginal soils. A field experiment was conducted to evaluate salinity tolerance potential, growth performance, carbon (δ¹³C) and nitrogen isotope composition (δ¹⁵N), intrinsic water use efficiency (iWUE), harvest index, and yield stability attributes in six barley genotypes (113/1B, 59/3A, N1-10, N1-29, Barjouj, Alanda01) at three salinity levels (0, 7, and 14 dS m^-1). The number of spikes m^-2 was highest in Alanda01 (620.8) while the lowest (556.2) was exhibited by Barjouj. Alanda01 produced the highest grain yield (3.96 t ha^-1), while the lowest yield was obtained in 59/3A (2.31 t ha^-1). Genotypes 113/1B, Barjouj, and Alanda01 demonstrate the highest negative δ¹³C values (-27.10‱, -26.49‱, -26.45‱), while the lowest values were obtained in N1-29 (-21.63‱) under salt stress. The δ¹⁵N was increased (4.93‱ and 4.59‱) after 7 and 14 dS m^-1 as compared to control (3.12‱). The iWUE was higher in N1-29 (144.5) and N1-10 (131.8), while lowest in Barjouj (81.4). Grain protein contents were higher in 113/1B and Barjouj than other genotypes. We concluded that salt tolerant barley genotypes can be cultivated in saline marginal soils for food and nutrition security and can help in the rehabilitation of marginal lands.

[Effects of long-term no-tillage and stover mulching on maize yield and its stability.]

Clarifying the differences of maize yield and its stability under long-term no-tillage with different stover mulching amounts can provide theoretical and technical supports for establishing and evaluating long-term conservation tillage pattern and promoting grain production. Based on a long-term conservation tillage field experiment in the mollisol area of Northeast China since 2007, we analyzed the interannual variation, variation coefficient and stability of maize yield during 2013 and 2019 across five treatments, i.e., no-tillage stover-free mulching (NT₀), no-tillage with 33% stover mulching (NT₃₃), no-tillage with 67% stover mulching (NT₆₇) and no-tillage with 100% stover mulching (NT₁₀₀), with the traditional ridge cropping (RT) as the control. The results showed that compared with RT, long-term no-tillage with stover mulching treatments could increase maize yield. NT₁₀₀ had the highest increasing rate of 11.4%, followed by NT₆₇ and NT₀, with the increasing rate of 11.0% and 10.4%, respectively. Maize yield exhibited a nonlinear relationship with the amount of stover mulch. The variation coefficient of maize yield under multi-year no-tillage with different stover mulching could be sorted as NT₆₇<RT<NT₁₀₀<NT₃₃<NT₀, and the yield sustainability index was NT₆₇>NT₀>NT₁₀₀>RT>NT₃₃, indicating that NT₆₇ treatment could significantly reduce the interannual fluctuation of maize yield and had better sustainability of yield. No-tillage stover mulching significantly increased soil total carbon and total nitrogen contents, which were significantly positively correlated with maize yield. In conclusion, compared with traditional tillage, no-tillage stover mulching could increase maize yield and soil carbon and nitrogen contents. Appropriate stover mulching (NT₆₇)had the potential to improve the stability and sustainability of maize yield.

Aus rice root architecture variation contributing to grain yield under drought suggests a key role of nodal root diameter class

The aus rice variety group originated in stress-prone regions and is a promising source for the development of new stress-tolerant rice cultivars. In this study, an aus panel (~220 genotypes) was evaluated in field trials under well-watered and drought conditions and in the greenhouse (basket, herbicide and lysimeter studies) to investigate relationships between grain yield and root architecture, and to identify component root traits behind the composite trait of deep root growth. In the field trials, high and stable grain yield was positively related to high and stable deep root growth (r = 0.16), which may indicate response to within-season soil moisture fluctuations (i.e., plasticity). When dissecting component traits related to deep root growth (including angle, elongation and branching), the number of nodal roots classified as 'large-diameter' was positively related to deep root growth (r = 0.24), and showed the highest number of colocated genome-wide association study (GWAS) peaks with grain yield under drought. The role of large-diameter nodal roots in deep root growth may be related to their branching potential. Two candidate loci that colocated for yield and root traits were identified that showed distinct haplotype distributions between contrasting yield/stability groups and could be good candidates to contribute to rice improvement.

Genes for Yield Stability in Tomatoes

Breeding plant varieties with adaptation to unstable environments requires some knowledge about the genetic control of yield stability. To further this goal, a meta-analysis of 12 years of field harvest data of 76 Solanum pennellii introgression lines (ILs) is conducted. Five quantitative trait loci (QTL) affecting yield stability are mapped; IL10-2-2 is unique as this introgression improved yield stability without affecting mean yield both in the historic data and in four years of field validations. Another dimension of the stability question is which genes when perturbed affect yield stability. For this the authors tested in the field 48 morphological mutants and found one 'canalization' mutant (canal-1) with a consistent effect of reducing the stability of a bouquet of traits including leaf variegation, plant size and yield. canal-1 mapped to a DNAJ chaperone gene (Solyc01g108200) whose homologues in C. elegans regulate phenotypic canalization. Additional alleles of canal-1 are generated using CRISPR/CAS9 and the resulting seedlings have uniform variegation suggesting that only specific changes in canal-1 can lead to unstable variegation and yield instability. The identification of IL10-2-2 demonstrates the value of historical phenotypic data for discovering genes for stability. It is also shown that a green-fruited wild species is a source of QTL to improve tomato yield stability.

In-Field Comparative Study of Landraces vs. Modern Wheat Genotypes under a Mediterranean Climate

The Near East climate ranges from arid to a Mediterranean, under which local wheat landraces have been grown for over millennia, assumingly accumulating a unique repertoire of genetic adaptations. In the current study, we subjected a subset of the Israeli Palestinian Landraces (IPLR) collection (n = 19: durum and bread wheat landraces, modern wheat cultivars, and landraces mixtures) to full-field evaluation. The multifield experiment included a semiarid site (2018-2019, 2019-2020) under low (L) and high (H) supplementary irrigation, and a Mediterranean site (2019-2020). Water availability had a major impact on crop performance. This was reflected in a strong discrimination between environments for biomass productivity and yield components. Compared to landraces, modern cultivars exhibited significantly higher grain yield (GY) across environments (+102%) reflecting the effect of the Green Revolution. However, under the Gilat19 (L) environment, this productivity gap was significantly reduced (only +39%). Five excelling landraces and the durum mix exhibited good agronomic potential across all trails. This was expressed in relatively high GY (2.3-2.85 t ha-1), early phenology (86-96 days to heading) and lodging resistance. Given the growing interest of stakeholders and consumers, these might be considered future candidates for the local artisanal wheat grain market. Yet, this step should be taken only after establishing an adjustable field management protocol.

A commentary on 'Significance of root hairs for plant performance under contrasting field conditions and water deficit'

This article comments on:

M. Marin, D. S. Feeney, L. K. Brown, M. Naveed, S. Ruiz, N. Koebernick, A. G. Bengough, P. D. Hallett, T. Roose, J. Puértolas, I. C. Dodd and T. S. George, Significance of root hairs for plant performance under contrasting field conditions and water deficit, Annals of Botany, Volume 128, Issue 1, 30 June 2021, Pages 3–18, 10.1093/aob/mcaa181

Establishment method affects rice root plasticity in response to drought and its relationship with grain yield stability

By responding to the variable soil environments in which they are grown, the roots of rice crops are likely to contribute to yield stability across a range of soil moistures, nutrient levels, and establishment methods. In this study, we explored different approaches to quantification of root plasticity and characterization of its relationship with yield stability. Using four different statistical approaches (plasticity index, slope, AMMI, and factor analytic) on a set of 17 genotypes including several recently-developed breeding lines targeted to dry direct-seeding, we identified only very few direct relationships between root plasticity and yield stability. However, genotypes identified as having combined yield stability and root plasticity showed higher grain yields across trials. Furthermore, root plasticity was expressed to a greater degree in puddled transplanted trials rather than under dry direct-seeding. Significant interactions between nitrogen and water resulted in contrasting relationships between nitrogen-use efficiency and biomass stability between puddled-transplanted and direct-seeded conditions. These results reflect the complex interaction between nitrogen, drought, and even different types of drought (as a result of the establishment method) on rice root growth, and suggest that although rice root plasticity may confer stable yield across a range of environments, it might be necessary to more narrowly define the targeted environments to which it will be most beneficial.

Comparing a Mixed Model Approach to Traditional Stability Estimators for Mapping Genotype by Environment Interactions and Yield Stability in Soybean [Glycine max (L.) Merr.]

Identifying genetic loci associated with yield stability has helped plant breeders and geneticists begin to understand the role and influence of genotype by environment (GxE) interactions in soybean [Glycine max (L.) Merr.] productivity, as well as other crops. Quantifying a genotype's range of performance across testing locations has been developed over decades with dozens of methodologies available. This includes directly modeling GxE interactions as part of an overall model for yield, as well as methods which generate overall yield "stability" values from multi-environment trial data. Correspondence between these methods as it pertains to the outcomes of genome wide association studies (GWAS) has not been well defined. In this study, the GWAS results for yield and yield stability were compared in 213 soybean lines across 11 environments to determine their utility and potential intersection. Both univariate and multivariate conventional stability estimates were considered alongside a mixed model for yield that fit marker by environment interactions as a random effect. One-hundred and six total QTL were discovered across all mapping results, however, genetic loci that were significant in the mixed model for grain yield that fit marker by environment interactions were completely distinct from those that were significant when mapping using traditional stability measures as a phenotype. Furthermore, 73.21% of QTL discovered in the mixed model were determined to cause a crossover interaction effect which cause genotype rank changes between environments. Overall, the QTL discovered via explicitly mapping GxE interactions also explained more yield variance that those QTL associated with differences in traditional stability estimates making their theoretical impact on selection greater. A lack of intersecting results between mapping approaches highlights the importance of examining stability in multiple contexts when attempting to manipulate GxE interactions in soybean.

Changes in rice yield and yield stability in China during the past six decades

BACKGROUND

Increasing rice yield and its stability are important to achieving the sustainability of rice production. Rice yields have increased substantially in China during recent decades, but information on the trend in yield stability has been limited. In this study, the trends in rice yield and rice yield stability from 1949 to 2015 were analysed in China's rice production.

RESULTS

The results showed that rice yields for all 16 provinces presented an increasing trend during the study period. The national annual rice yield gain was 86.0 kg ha^-1 during the last six decades, varying from 48.4 to 106.0 kg ha^-1 in different provinces and exhibiting linear, bilinear, or trilinear relationships. Remarkably, the annual yield increase was smaller in provinces dominated by double rice cropping systems than in the other provinces. Notably, rice yield stagnations have occurred in recent years at provincial and national levels. Absolute residuals over time showed slight increases in four of 16 provinces, indicating a reduction in yield stability in these four provinces. However, the relative yield residuals exhibited a clear trend towards increased yield stability for all 16 provinces. The rice yields of newer cultivars planted with improved crop management practices were consistently higher and more stable than with cultivars from the beginning of the study period.

CONCLUSION

This study revealed that rice yield in China has increased substantially, accompanied by improved stability over the last six decades. Given the spatial difference, this study emphasizes the priority of orienting long-term on-farm studies to investigate yield stability. © 2020 Society of Chemical Industry.

Current status and prospects of common buckwheat breeding in Japan

In this review, the current status and prospects of common buckwheat (Fagopyrum esculentum Moench.) breeding in Japan are summarized. The varieties that have been registered in Japan so far are introduced with details regarding their breeding source populations and breeding methods. Because the main breeding method used for common buckwheat is mass selection, the merits and demerits of this method are explored from the perspective of heritability. Although there are many breeding objectives in common buckwheat, high yield and yield stability are discussed here. Regarding the potential of common buckwheat breeding in the future, the prospects of effective exploitation of self-fertility and selection based on genomic information are examined.

Pea Efficiency of Post-drought Recovery Relies on the Strategy to Fine-Tune Nitrogen Nutrition

As drought is increasingly frequent in the context of climate change it is a major constraint for crop growth and yield. The ability of plants to maintain their yield in response to drought depends not only on their ability to tolerate drought, but also on their capacity to subsequently recover. Post-stress recovery can indeed be decisive for drought resilience and yield stability. Pea (Pisum sativum), as a legume, has the capacity to fix atmospheric nitrogen through its symbiotic interaction with soil bacteria within root nodules. Biological nitrogen fixation is highly sensitive to drought which can impact plant nitrogen nutrition and growth. Our study aimed at dynamically evaluating whether the control of plant N status after drought could affect nodulated pea plant's ability to recover. Two pea genotypes, Puget and Kayanne, displaying different drought resilience abilities were compared for their capacity to tolerate to, and to recover from, a 2-weeks water-deficit period applied before flowering. Physiological processes were studied in this time-series experiment using a conceptual structure-function analysis framework focusing on whole plant carbon, nitrogen, and water fluxes combined to two 13CO2 and 15N2 labeling experiments. While Puget showed a yield decrease compared to well-watered plants, Kayanne was able to maintain its yield. During the recovery period, genotype-dependent strategies were observed. The analysis of the synchronization of carbon, nitrogen, and water related traits dynamics during the recovery period and at the whole plant level, revealed that plant growth recovery was tightly linked to N nutrition. In Puget, the initiation of new nodules after water deficit was delayed compared to control plants, and additional nodules developed, while in Kayanne the formation of nodules was both rapidly and strictly re-adjusted to plant growth needs, allowing a full recovery. Our study suggested that a rapid re-launch of N acquisition, associated with a fine-tuning of nodule formation during the post-stress period is essential for efficient drought resilience in pea leading to yield stability.

Capturing Maize Stand Heterogeneity Across Yield-Stability Zones Using Unmanned Aerial Vehicles (UAV)

Despite the new equipment capabilities, uneven crop stands are still common occurrences in crop fields, mainly due to spatial heterogeneity in soil conditions, seedling mortality due to herbivore predation and disease, or human error. Non-uniform plant stands may reduce grain yield in crops like maize. Thus, detecting signs of variability in crop stand density early in the season provides critical information for management decisions and crop yield forecasts. Processing techniques applied on images captured by unmanned aerial vehicles (UAVs) has been used successfully to identify crop rows and estimate stand density and, most recently, to estimate plant-to-plant interval distance. Here, we further test and apply an image processing algorithm on UAV images collected from yield-stability zones in a commercial crop field. Our objective was to implement the algorithm to compare variation of plant-spacing intervals to test whether yield differences within these zones are related to differences in crop stand characteristics. Our analysis indicates that the algorithm can be reliably used to estimate plant counts (precision >95% and recall >97%) and plant distance interval (R² ~0.9 and relative error <10%). Analysis of the collected data indicated that plant spacing variability differences were small among plots with large yield differences, suggesting that it was not a major cause of yield variability across zones with distinct yield history. This analysis provides an example of how plant-detection algorithms can be applied to improve the understanding of patterns of spatial and temporal yield variability.

Marine reserves stabilize fish populations and fisheries yields in disturbed coral reef systems

Marine reserve networks are increasingly implemented to conserve biodiversity and enhance the persistence and resilience of exploited species and ecosystems. However, the efficacy of marine reserve networks in frequently disturbed systems, such as coral reefs, has rarely been evaluated. Here we analyze a well-mixed larval pool model and a spatially explicit model based on a well-documented coral trout (Plectropomus spp.) metapopulation in the Great Barrier Reef Marine Park, Australia, to determine the effects of marine reserve coverage and placement (in relation to larval connectivity and disturbance heterogeneity) on the temporal stability of fisheries yields and population biomass in environmentally disturbed systems. We show that marine reserves can contribute to stabilizing fishery yield while increasing metapopulation persistence, irrespective of whether reserves enhance or diminish average fishery yields. However, reserve placement and the level of larval connectivity among subpopulations were important factors affecting the stability and sustainability of fisheries and fish metapopulations. Protecting a mix of disturbed and non-disturbed reefs, rather than focusing on the least-disturbed habitats, was the most consistently beneficial approach across a range of dispersal and reserve coverage scenarios. Placing reserves only in non-disturbed areas was the most beneficial for biomass enhancement, but had variable results for fisheries and could potentially destabilize yields in systems with well-mixed larval or those that are moderately fished. We also found that focusing protection on highly disturbed areas could actually increase variability in yields and biomass, especially when degraded reef reserves were distant and poorly connected to the meta-population. Our findings have implications for the design and implementation of reserve networks in the presence of stochastic, patchy environmental disturbances.

Stability of wheat grain yields over three field seasons in the UK

Ensuring food security in a changing climate is a major contemporary challenge and requires development of climate-resilient crops that perform well under variable environments. The hypothesis that yield stability in suboptimal conditions is linked to yield penalties in optimal conditions was investigated in field-grown wheat in the UK. The phenotypic responses, rate of wheat crop development, and final grain yield to varying sowing date, rainfall, air temperature, and radiation patterns were studied for a panel of 61 elite commercial wheat cultivars grown in the UK in 2012, 2013, and 2014. Contrasting climatic patterns, particularly rainfall accumulation and distribution over the season, influenced the relative performance of the cultivars affecting the duration of grain development stage and impacting on productivity. Indices for crop productivity, yield stability, and performance under suboptimal conditions revealed four cultivars with a combination of stable and high relative grain yields over the three seasons: Gladiator, Humber, Mercato, and Zebedee. Genetic similarity between cultivars partially explained yield performance in the contrasting seasons. The year of release of the cultivars correlated with grain yield but not with yield stability, supporting the contention that breeding for yield potential does not select for climate resilience and yield stability of crops. Further analysis of the outstanding cultivars may unravel target traits for breeding efforts aimed at increasing wheat yield potential and stability in the changing climate.

Drought tolerance during reproductive development is important for increasing wheat yield potential under climate change in Europe

Drought stress during reproductive development could drastically reduce wheat grain number and yield, but quantitative evaluation of such an effect is unknown under climate change. The objectives of this study were to evaluate potential yield benefits of drought tolerance during reproductive development for wheat ideotypes under climate change in Europe, and to identify potential cultivar parameters for improvement. We used the Sirius wheat model to optimize drought-tolerant (DT) and drought-sensitive (DS) wheat ideotypes under a future 2050 climate scenario at 13 contrasting sites, representing major wheat growing regions in Europe. Averaged over the sites, DT ideotypes achieved 13.4% greater yield compared with DS, with higher yield stability. However, the performances of the ideotypes were site dependent. Mean yield of DT was 28-37% greater compared with DS in southern Europe. In contrast, no yield difference (≤1%) between ideotypes was found in north-western Europe. An intermediate yield benefit of 10-23% was found due to drought tolerance in central and eastern Europe. We conclude that tolerance to drought stress during reproductive development is important for high yield potentials and greater yield stability of wheat under climate change in Europe.

Designer Roots for Future Crops

Despite the importance of roots, they have largely been ignored by modern crop research and breeding. We discuss important progress in crop root research and highlight how the context-dependent optimisation of below- and above-ground plant components provides opportunities to improve future crops in the face of increasing environmental fluctuations.

Phenotypic Description of Theobroma cacao L. for Yield and Vigor Traits From 34 Hybrid Families in Costa Rica Based on the Genetic Basis of the Parental Population

A comprehensive understanding of the genetic basis of target traits in any crop is critical to design breeding strategies for the development and release of new improved varieties. In this study, 34 cacao families were evaluated for vigor and yield related traits over the course of 6 years in Costa Rica. Linear mixed models provided the variance components for the partitioning of additive and non-additive effects. Heritabilities of yield over time ranged from 0.085 to 0.576, from 0.127 to 0.399 for vigor, and 0.141 to 0.146 for disease resistance traits. Significant (p < 0.001) general combining abilities were observed for ICS-43 and LcTeen-37 with negative effect on average yield (-0.674, -0.690), respectively. Specific combining abilities for yield had significant (p < 0.001) positive effect from the cross GU-154-L x UF-273 Type 2 (0.703) and strong negative interaction between ICS-43 and LF-1 (-0.975). A weighted index was used to select the top performers while providing the corresponding genetic gains. At an 1% selection intensity, yield component gains ranged from 17.8 to 331.9%. Agronomic traits such as branch angle, trunk diameter and jorquette height had lower genetic gains and lower heritabilities. In addition, the parents in this study were genotyped with a 96-SNP marker off-typing set and a significant positive correlation of 0.39 (p = 0.019) was found between genetic distance and specific combining abilities for yield. Preliminary comparison of clonal parents vs. seedlings yield in the family with the highest SCA suggest for the first time presence of heterobeltiosis in cacao.

Translating knowledge about abiotic stress tolerance to breeding programmes

Plant breeding and improvements in agronomic practice are making a consistent contribution to increasing global crop production year upon year. However, the rate of yield improvement currently lags behind the targets set to produce enough food to meet the demands of the predicted global population in 2050. Furthermore, crops that are exposed to harmful abiotic environmental factors (abiotic stresses, e.g. water limitation, salinity, extreme temperature) are prone to reduced yields. Here, we briefly describe the processes undertaken in conventional breeding programmes, which are usually designed to improve yields in near-optimal conditions rather than specifically breeding for improved crop yield stability under stressed conditions. While there is extensive fundamental research activity that examines mechanisms of plant stress tolerance, there are few examples that apply this research to improving commercial crop yields. There are notable exceptions, and we highlight some of these to demonstrate the magnitude of yield gains that could be made by translating agronomic, phenological and genetic solutions focused on improving or mitigating the effect of abiotic stress in the field; in particular, we focus on improvements in crop water-use efficiency and salinity tolerance. We speculate upon the reasons for the disconnect between research and research translation. We conclude that to realise untapped rapid gains towards food security targets new funding structures need to be embraced. Such funding needs to serve both the core and collaborative activities of the fundamental, pre-breeding and breeding research communities in order to expedite the translation of innovative research into the fields of primary producers.

Impact of disease on diversity and productivity of plant populations

Experiments were conducted on the role of intra- and inter-genotypic competition in ecological processes operating at the population scale in diseased plant populations.Combinations of Arabidopsis thaliana genotypes showing variation for phenotypic traits relating to competitive ability and pathogen compatibility were infected with the oomycete Hyaloperonospora arabidopsidis and Turnip yellows virus in separate experiments. Plant fitness and competitive ability were estimated from phenotypic measurements.Pathogen-induced reduction in competitive ability for susceptible genotypes increased the competitive ability of resistant genotypes, resulting in maintenance of yield via competitive release. The two diseases had different effects on competitive interactions between plants. In experiments involving the oomycete, the highest yields were produced by mixtures of two weakly competing genotypes.The Arabidopsis model system has elucidated the ecological processes by which compensatory competitive interactions can increase the buffering capacity of plant populations under pathogen attack. Highly competitive genotypes may not maximize the productivity of the population as a whole, as they may over-yield at the expense of less competitive, more productive genotypes. The specific outcomes of competitive interactions cannot be generalized because they depend on the disease and the host genotypes.

In silico system analysis of physiological traits determining grain yield and protein concentration for wheat as influenced by climate and crop management

Genetic improvement of grain yield (GY) and grain protein concentration (GPC) is impeded by large genotype×environment×management interactions and by compensatory effects between traits. Here global uncertainty and sensitivity analyses of the process-based wheat model SiriusQuality2 were conducted with the aim of identifying candidate traits to increase GY and GPC. Three contrasted European sites were selected and simulations were performed using long-term weather data and two nitrogen (N) treatments in order to quantify the effect of parameter uncertainty on GY and GPC under variable environments. The overall influence of all 75 plant parameters of SiriusQuality2 was first analysed using the Morris method. Forty-one influential parameters were identified and their individual (first-order) and total effects on the model outputs were investigated using the extended Fourier amplitude sensitivity test. The overall effect of the parameters was dominated by their interactions with other parameters. Under high N supply, a few influential parameters with respect to GY were identified (e.g. radiation use efficiency, potential duration of grain filling, and phyllochron). However, under low N, >10 parameters showed similar effects on GY and GPC. All parameters had opposite effects on GY and GPC, but leaf and stem N storage capacity appeared as good candidate traits to change the intercept of the negative relationship between GY and GPC. This study provides a system analysis of traits determining GY and GPC under variable environments and delivers valuable information to prioritize model development and experimental work.

Stability, across environments, of grain and alcohol yield, in soft wheat varieties grown for grain distilling or bioethanol production

BACKGROUND

Soft-milling wheat has potential use for both grain whisky distilling and bioethanol production. Varietal comparisons over wide-ranging environments would permit assessment of both grain and alcohol yield potential and also permit the stability across environments, for these parameters, to be compared.

RESULTS

For 12 varieties, analysis of variance showed highly significant effects of variety, site, season and fertiliser application on grain and alcohol yield. There were also significant interactions between these factors and, consequently, varieties varied in stability across environments as well as in mean values for the parameters assessed. Alcohol production per hectare was affected more strongly by variation in grain yield than alcohol yield, but increasing grain protein content reduced alcohol yield and, therefore, utility for grain distilling.

CONCLUSION

To maximise energy production, the best varieties for bioethanol would combine high and stable grain yield with slower reduction of alcohol yield as grain protein increases. For grain distilling, where the energy balance is less important, high alcohol yield will remain the key factor. Data derived using near infrared spectroscopy can be valuable in assessing stability of quality traits across environments.

Impact of swapping soils on the endophytic bacterial communities of pre-domesticated, ancient and modern maize

BACKGROUND

Endophytes are microbes that live within plants such as maize (corn, Zea mays L.) without causing disease. It is generally assumed that most endophytes originate from soil. If this is true, then as humans collected, domesticated, bred and migrated maize globally from its native Mexico, they moved the species away from its native population of endophyte donors. The migration of maize persists today, as breeders collect wild and exotic seed (as sources of diverse alleles) from sites of high genetic diversity in Mexico for breeding programs on distant soils. When transported to new lands, it is unclear whether maize permits only selective colonization of microbes from the Mexican soils on which it co-evolved, tolerates shifts in soil-derived endophytes, or prevents colonization of soil-based microbes in favour of seed-transmitted microbes. To test these hypotheses, non-sterilized seeds of three types of maize (pre-domesticated-Mexican, ancient-Mexican, modern-temperate) were planted side-by-side on indigenous Mexican soil, Canadian temperate soil or sterilized sand. The impact of these soil swaps on founder bacterial endophyte communities was tested using 16S-rDNA profiling, culturing and microbial trait phenotyping.

RESULTS

Multivariate analysis showed that bacterial 16S-rDNA TRFLP profiles from young, surface-sterilized maize plants were more similar when the same host genotype was grown on the different soils than when different maize genotypes were grown on the same soil. There appeared to be two reasons for this result. First, the largest fraction of bacterial 16S-signals from soil-grown plants was shared with parental seeds and/or plants grown on sterilized sand, suggesting significant inheritance of candidate endophytes. The in vitro activities of soil-derived candidate endophytes could be provided by bacteria that were isolated from sterile sand grown plants. Second, many non-inherited 16S-signals from sibling plants grown on geographically-distant soils were shared with one another, suggesting maize can select microbes with similar TRFLP peak sizes from diverse soils. Wild, pre-domesticated maize did not possess more unique 16S-signals when grown on its native Mexican soil than on Canadian soil, pointing against long-term co-evolutionary selection. The modern hybrid did not reject more soil-derived 16S-signals than did ancestral maize, pointing against such rejection as a mechanism that contributes to yield stability across environments. A minor fraction of 16S-signals was uniquely associated with any one soil.

CONCLUSION

Within the limits of TRFLP profiling, the candidate bacterial endophyte populations of pre-domesticated, ancient and modern maize are partially buffered against the effects of geographic migration --- from a Mexican soil associated with ancestral maize, to a Canadian soil associated with modern hybrid agriculture. These results have implications for understanding the effects of domestication, migration, ex situ seed conservation and modern breeding, on the microbiome of one of the world's most important food crops.

Is proline accumulation per se correlated with stress tolerance or is proline homeostasis a more critical issue?

Proline has been recognized as a multi-functional molecule, accumulating in high concentrations in response to a variety of abiotic stresses. It is able to protect cells from damage by acting as both an osmotic agent and a radical scavenger. Proline accumulated during a stress episode is degraded to provide a supply of energy to drive growth once the stress is relieved. Proline homeostasis is important for actively dividing cells as it helps to maintain sustainable growth under long-term stress. It also underpins the importance of the expansion of the proline sink during the transition from vegetative to reproductive growth and the initiation of seed development. Its role in the reproductive tissue is to stabilize seed set and productivity. Thus, to cope with abiotic stress, it is important to develop strategies to increase the proline sink in the reproductive tissue. We give a holistic account of proline homeostasis, taking into account the regulation of proline synthesis, its catabolism, and intra- and intercellular transport, all of which are vital components of growth and development in plants challenged by stress.

Stabilization of yield in plant genotype mixtures through compensation rather than complementation

BACKGROUND AND AIMS

Plant genotypic mixtures have the potential to increase yield stability in variable, often unpredictable environments, yet knowledge of the specific mechanisms underlying enhanced yield stability remains limited. Field studies are constrained by environmental conditions which cannot be fully controlled and thus reproduced. A suitable model system would allow reproducible experiments on processes operating within crop genetic mixtures.

METHODS

Phenotypically dissimilar genotypes of Arabidopsis thaliana were grown in monocultures and mixtures under high levels of competition for abiotic resources. Seed production, flowering time and rosette size were recorded.

KEY RESULTS

Mixtures achieved high yield stability across environments through compensatory interactions. Compensation was greatest when plants were under high levels of heat and nutrient stress. Competitive ability and mixture performance were predictable from above-ground phenotypic traits even though below-ground competition appeared to be more intense.

CONCLUSIONS

This study indicates that the mixing ability of plant genotypes can be predicted from their phenotypes expressed in a range of relevant environments, and implies that a phenotypic screen of genotypes could improve the selection of suitable components of genotypic mixtures in agriculture intended to be resilient to environmental stress.