The cropping system matters - Contrasting responses of winter faba bean (Vicia faba L.) genotypes to drought stress

Intercropping of legumes and cereals provides many ecological advantages and contributes to a sustainable agriculture. These agricultural systems face ongoing shifts in precipitation patterns and seasonal drought. Although the effect of drought stress on legumes has been frequently studied, knowledge about water deficits influencing legumes under different cropping systems is still limited. Therefore, we investigated the impact of water deficit and re-irrigation on two winter faba bean genotypes (S_004 and S_062) and winter wheat (var. Genius) in pure and intercropped stands under greenhouse conditions. Various physiological and biochemical parameters, such as canopy surface temperature, leaf relative water content and proline content, were collected at three time points (beginning of water deficit, end of water deficit, after re-irrigation). In addition, water use efficiency (WUE) was analyzed at the end of the experiment. The overall drought stress tolerance was determined as conceptual analysis of all measured parameters. Water deficit significantly affected WUE, surface temperature and proline content of both winter faba bean genotypes. Interestingly, intercropping with wheat resulted in an overall high drought tolerance of genotype S_004, while genotype S_062 had a high drought tolerance in pure stands. Under water deficit, pure stands of S_062 substantially increased WUE by 30.5%. Intercropping of genotype S_004 increased the dry matter per plant by 31.7% compared to pure stands under water deficit. Contrary, intercropping of genotype S_062 did not improve the dry matter production. Our findings indicate that genotype S_004 benefits from resource complementarity in intercropping systems with wheat, whereas S_062 is better suitable for pure stands due to competitive effects. Thus, our study highlights that the drought tolerance of winter faba bean genotypes depends on the cropping system, leading to a demand for drought-adapted cultivars specifically selected for intercropping.

Quantity of supplementary LED lightings regulates photosynthetic apparatus, improves photosynthetic capacity and enhances productivity of Cos lettuce grown in a tropical greenhouse

Although cooling their rootzone allows year-round (temperate) vegetable production in Singapore's warm climate, these crops have frequently experienced increasingly unpredictable cloudy and hazy weather. Supplementary lighting with light-emitting diodes (LEDs) could be used to reduce the impacts of low light intensity. This study investigated the responses of temperate Cos lettuce (Lactuca sativa L.) to different quantities (photosynthetic photon flux density, PPFD of 0, 150, 300 µmol m-2 s-1) of supplementary LED lightings in the tropical greenhouse. Increasing light intensity significantly increased total leaf area, shoot and root fresh weight (FW) and dry weight (DW), total chlorophyll (Chl) and carotenoids (Car) contents, light-saturated photosynthetic CO2 assimilation rate (Asat) and transpiration rate (Tr). There were no significant differences in Fv/Fm ratio, total reduced nitrogen, specific leaf area (SLA) and PSII concentration among the three light treatments. However, there was an increasing trend with increasing light intensity for Chl a/b ratio, net photosynthetic O2 evolution rate (PN), cytochrome b6f (Cyt b6f), leaf total soluble protein and Rubisco concentrations. This study provides the basic understanding of photosynthetic apparatus and capacity of temperate crops grown under different supplementary LED lightings in the tropical greenhouse.

Tuning Beforehand: A Foresight on RNA Interference (RNAi) and In Vitro-Derived dsRNAs to Enhance Crop Resilience to Biotic and Abiotic Stresses

Crop yield is severely affected by biotic and abiotic stresses. Plants adapt to these stresses mainly through gene expression reprogramming at the transcriptional and post-transcriptional levels. Recently, the exogenous application of double-stranded RNAs (dsRNAs) and RNA interference (RNAi) technology has emerged as a sustainable and publicly acceptable alternative to genetic transformation, hence, small RNAs (micro-RNAs and small interfering RNAs) have an important role in combating biotic and abiotic stresses in plants. RNAi limits the transcript level by either suppressing transcription (transcriptional gene silencing) or activating sequence-specific RNA degradation (post-transcriptional gene silencing). Using RNAi tools and their respective targets in abiotic stress responses in many crops is well documented. Many miRNAs families are reported in plant tolerance response or adaptation to drought, salinity, and temperature stresses. In biotic stress, the spray-induced gene silencing (SIGS) provides an intelligent method of using dsRNA as a trigger to silence target genes in pests and pathogens without producing side effects such as those caused by chemical pesticides. In this review, we focus on the potential of SIGS as the most recent application of RNAi in agriculture and point out the trends, challenges, and risks of production technologies. Additionally, we provide insights into the potential applications of exogenous RNAi against biotic stresses. We also review the current status of RNAi/miRNA tools and their respective targets on abiotic stress and the most common responsive miRNA families triggered by stress conditions in different crop species.

Interactive effects of plant growth-promoting rhizobacteria and a seaweed extract on the growth and physiology of Allium cepa L. (onion)

Detrimental effects caused by the overuse of synthetic agrochemicals have led to the development of natural biostimulants such as seaweed extracts and plant growth-promoting rhizobacteria (PGPR) being used as an alternative, environmentally-friendly technology to improve crop growth and increase agricultural yields. The present study aimed to investigate the interactions between PGPR and a commercial seaweed extract on the growth and biochemical composition of onion (Allium cepa). A pot trial was conducted under greenhouse conditions where onion plants were treated individually with the two PGPR, namely Bacillus licheniformis (BL) and Pseudomonas fluorescens (PF) and a seaweed extract Kelpak® (KEL) and combinations of KEL + BL and KEL + PF. Growth and yield parameters were measured after 12 weeks. KEL-treated plants showed the best growth response and overcame the inhibitory effects of BL treatment. KEL-treated plants also had the highest chlorophyll content. PGPR application improved the mineral nutrition of onion with these plants having the highest mineral content in the leaves and bulb. All biostimulant treatments increased the endogenous cytokinin and auxin content with the highest concentrations generally detected in the PF-treated plants. These results suggest that co-application of different biostimulant classes with different modes of action could further increase crop productivity with an improvement in both growth and nutrition content being achieved in onion with the co-application of a seaweed extract and PGPR.

Nanotechnology and artificial intelligence to enable sustainable and precision agriculture

Climate change, increasing populations, competing demands on land for production of biofuels and declining soil quality are challenging global food security. Finding sustainable solutions requires bold new approaches and integration of knowledge from diverse fields, such as materials science and informatics. The convergence of precision agriculture, in which farmers respond in real time to changes in crop growth with nanotechnology and artificial intelligence, offers exciting opportunities for sustainable food production. Coupling existing models for nutrient cycling and crop productivity with nanoinformatics approaches to optimize targeting, uptake, delivery, nutrient capture and long-term impacts on soil microbial communities will enable design of nanoscale agrochemicals that combine optimal safety and functionality profiles.

Conservation outreach that acknowledges human contributions to climate change does not inhibit action by U.S. farmers: Evidence from a large randomized controlled trial embedded in a federal program on soil health

Technologies and practices that reduce the environmental impacts of US agriculture are well documented. Less is known about how best to encourage their adoption. We report on the results of a large randomized controlled trial conducted with nearly 10,000 agricultural producers in the United States. The experiment was embedded in US Department of Agriculture outreach efforts to improve soil conservation practices. USDA varied the content of mailings to test two sets of competing theories about outreach to agricultural producers. Contrary to conventional wisdom, we find no evidence that acknowledging the link between climate change and agricultural production discourages conservation action. Furthermore, we find that producers who were invited to a webinar were less likely to take any action to learn more about conservation practices than producers who were not told about the webinar, a result that runs counter to the popular wisdom that offering more options leads to more action.

Trifolium subterraneum cover cropping for improving the nutritional status of a Mediterranean apricot orchard

BACKGROUND

The utilization of Trifolium subterraneum L. cover crops may represent an innovative and efficient option in low-input and organic farming, especially in Mediterranean agroecosystems where low and irregular rainfall require frequent soil tillage and use of herbicides to reduce moisture losses and weed competitiveness. Since imbalances of soil macro- and micro-nutrients due to cover cropping establishment could be responsible for numerous problems in specialized orchards, such as disturbances in the normal tree growth and quality of fruits, the objective of this study was to investigate, the cumulative effects of a 3-years established T. subterraneum cover cropping, compared with a spontaneous flora and a conventional management (as a control), on the levels of mineral nutrients in the apricot leaves and fruits.

RESULTS

Our findings indicated that T. subterraneum cover cropping tended to stimulate higher leaf macro- and micro-nutrients content than conventional management and flora spontaneous cover cropping. In addition, the presence of T. subterraneum cover cropping, especially with the incorporation of dead mulches into the soil, increased the content of potassium (K), nitrogen (N), calcium (Ca), iron (Fe) and manganese (Mn) in apricot fruits.

CONCLUSION

Taking also into account the effects of T. subterraneum cover cropping on both the reduction of soil weed and enhancement of bacteria communities involved in the soil N-cycle, we may suggest its application in Mediterranean orchards as an eco-friendly alternative to synthetic herbicides for weed control and mineral N fertilizers, while enhancing the apricot tree nutritional status and fruit quality. © 2020 Society of Chemical Industry.

Trifolium subterraneum cover cropping for improving the nutritional status of a Mediterranean apricot orchard

BACKGROUND

The utilization of Trifolium subterraneum L. cover crops may represent an innovative and efficient option in low-input and organic farming, especially in Mediterranean agroecosystems where low and irregular rainfall require frequent soil tillage and use of herbicides to reduce moisture losses and weed competitiveness. Since imbalances of soil macro- and micro-nutrients due to cover cropping establishment could be responsible for numerous problems in specialized orchards, such as disturbances in the normal tree growth and quality of fruits, the objective of this study was to investigate, the cumulative effects of a 3-years established T. subterraneum cover cropping, compared with a spontaneous flora and a conventional management (as a control), on the levels of mineral nutrients in the apricot leaves and fruits.

RESULTS

Our findings indicated that T. subterraneum cover cropping tended to stimulate higher leaf macro- and micro-nutrients content than conventional management and flora spontaneous cover cropping. In addition, the presence of T. subterraneum cover cropping, especially with the incorporation of dead mulches into the soil, increased the content of potassium (K), nitrogen (N), calcium (Ca), iron (Fe) and manganese (Mn) in apricot fruits.

CONCLUSION

Taking also into account the effects of T. subterraneum cover cropping on both the reduction of soil weed and enhancement of bacteria communities involved in the soil N-cycle, we may suggest its application in Mediterranean orchards as an eco-friendly alternative to synthetic herbicides for weed control and mineral N fertilizers, while enhancing the apricot tree nutritional status and fruit quality. © 2020 Society of Chemical Industry.

Towards a dynamic photosynthesis model to guide yield improvement in C4 crops

The most productive C4 food and biofuel crops, such as Saccharum officinarum (sugarcane), Sorghum bicolor (sorghum) and Zea mays (maize), all use NADP-ME-type C4 photosynthesis. Despite high productivities, these crops fall well short of the theoretical maximum solar conversion efficiency of 6%. Understanding the basis of these inefficiencies is key for bioengineering and breeding strategies to increase the sustainable productivity of these major C4 crops. Photosynthesis is studied predominantly at steady state in saturating light. In field stands of these crops light is continually changing, and often with rapid fluctuations. Although light may change in a second, the adjustment of photosynthesis may take many minutes, leading to inefficiencies. We measured the rates of CO₂ uptake and stomatal conductance of maize, sorghum and sugarcane under fluctuating light regimes. The gas exchange results were combined with a new dynamic photosynthesis model to infer the limiting factors under non-steady-state conditions. The dynamic photosynthesis model was developed from an existing C4 metabolic model for maize and extended to include: (i) post-translational regulation of key photosynthetic enzymes and their temperature responses; (ii) dynamic stomatal conductance; and (iii) leaf energy balance. Testing the model outputs against measured rates of leaf CO₂ uptake and stomatal conductance in the three C4 crops indicated that Rubisco activase, the pyruvate phosphate dikinase regulatory protein and stomatal conductance are the major limitations to the efficiency of NADP-ME-type C4 photosynthesis during dark-to-high light transitions. We propose that the level of influence of these limiting factors make them targets for bioengineering the improved photosynthetic efficiency of these key crops.

Diversity increases yield but reduces harvest index in crop mixtures

Resource allocation to reproduction is a critical trait for plant fitness^1,2. This trait, called harvest index in the agricultural context^3-5, determines how plant biomass is converted to seed yield and consequently financial revenue from numerous major staple crops. While plant diversity has been demonstrated to increase plant biomass^6-8, plant diversity effects on seed yield of crops are ambiguous⁹ and dependent on the production syndrome¹⁰. This discrepancy might be explained through changes in the proportion of resources invested in reproduction in response to changes in plant diversity, namely through changes in species interactions and microenvironmental conditions^11-14. Here, we show that increasing crop plant diversity from monocultures over two- to four-species mixtures increased annual primary productivity, resulting in overall higher plant biomass and, to a lesser extent, higher seed yield in mixtures compared with monocultures. The difference between the two responses to diversity was due to a reduced harvest index of the eight tested crop species in mixtures, possibly because their common cultivars have been bred for maximum performance in monoculture. While crop diversification provides a sustainable measure of agricultural intensification¹⁵, the use of currently available cultivars may compromise larger gains in seed yield. We therefore advocate regional breeding programmes for crop varieties to be used in mixtures that should exploit complementarity¹⁶ among crop species.

Influence of rice varieties, organic manure and water management on greenhouse gas emissions from paddy rice soils

The study is focused on impact of manure application, rice varieties and water management on greenhouse gas (GHG) emissions from paddy rice soil in pot experiment. The objectives of this study were a) to assess the effect of different types of manure amendments and rice varieties on greenhouse gas emissions and b) to determine the optimum manure application rate to increase rice yield while mitigating GHG emissions under alternate wetting and drying irrigation in paddy rice production. The first pot experiment was conducted at the Department of Agronomy, Yezin Agricultural University, Myanmar, in the wet season from June to October 2016. Two different organic manures (compost and cow dung) and control (no manure), and two rice varieties; Manawthukha (135 days) and IR-50 (115 days), were tested. The results showed that cumulative CH₄ emission from Manawthukha (1.084 g CH₄ kg^-1 soil) was significantly higher than that from IR-50 (0.683 g CH₄ kg^-1 soil) (P<0.0046) with yield increase (P<0.0164) because of the longer growth duration of the former. In contrast, higher cumulative nitrous oxide emissions were found for IR-50 (2.644 mg N₂O kg^-1 soil) than for Manawthukha (2.585 mg N₂O kg^-1 soil). However, IR-50 showed less global warming potential (GWP) than Manawthukha (P<0.0050). Although not significant, the numerically lowest CH₄ and N₂O emissions were observed in the cow dung manure treatment (0.808 g CH₄ kg^-1 soil, 2.135 mg N₂O kg^-1 soil) compared to those of the control and compost. To determine the effect of water management and organic manures on greenhouse gas emissions, second pot experiments were conducted in Madaya township during the dry and wet seasons from February to October 2017. Two water management practices {continuous flooding (CF) and alternate wetting and drying (AWD)} and four cow dung manure rates {(1) 0 (2) 2.5 t ha^-1 (3) 5 t ha^-1 (4) 7.5 t ha^-1} were tested. The different cow dung manure rates did not significantly affect grain yield or greenhouse gas emissions in this experiment. Across the manure treatments, AWD irrigation significantly reduced CH₄ emissions by 70% during the dry season and 66% during the wet season. Although a relative increase in N₂O emissions under AWD was observed in both rice seasons, the global warming potential was significantly reduced in AWD compared to CF in both seasons (P<0.0002, P<0.0000) according to reduced emission in CH₄. Therefore, AWD is the effective mitigation practice for reducing GWP without compromising rice yield while manure amendment had no significant effect on GHG emission from paddy rice field. Besides, AWD saved water about 10% in dry season and 19% in wet season.

Modelling smallholder farmers' preferences for soil fertility management technologies in Benin: A stated preference approach

The decline of soil fertility is a major constraint which results in lower levels of crop productivity, agricultural development and food security in Sub-Saharan Africa. This study is the first to perform a focalized investigation on the most interesting technological profiles to offer to each category of producers in Benin agricultural development hubs (ADHs) using the stated preference method, more precisely, the improved choice experiment method. The investigation focused on 1047 sampled plots from 962 randomly selected producers in villages of the Smallholder Agricultural Productivity Enhancement Program in Sub-Saharan Africa of the ADHs. An analysis of the experimental choice data with the endogenous attribute attendance and the latent class models was carried out to account for the attribute non-attendance phenomenon and the heterogeneity of the producers' preferences. However, three classes of producer with different socio-economic, demographic, and soil physicochemical characteristics were identified. Thus, the heterogeneity of preferences was correlated with the attributes linked to the cost, sustainability, and frequency of plot maintenance. All producers, regardless of the ADHs, had a strong attachment to accessibility of technologies with short time restoration of soil fertility, and the ability to obtain additional benefits. These latest attributes, added to that relating to cost, tended to have a low probability of rejection in the decision-making process. These results have implications for local decision-makers facing the complex problem of resolving land degradation and local economic development challenges. The generalizability of these findings provides useful insight and direction for future studies in Sub-Saharan Africa.

Evaluation of Jatropha curcas L. leaves mulching on wheat growth and biochemical attributes under water stress

BACKGROUND

Organic mulches are widely used in crop production systems. Due to their benefits in improving soil fertility, retention of soil moisture and weed control. Field experiments were conducted during wheat growing seasons of 2018-2019 and 2019-2020 to evaluate the effects of Jatropha leaves mulch on the growth of wheat varieties 'Wadan-17' (rainfed) and 'Pirsabaq-2013' (irrigated) under well irrigated and water stress conditions (non-irrigated maintaining 40% soil field capacity). Jatropha mulch was applied to the soil surface at 0, 1, 3 and 5 Mg ha^-1 before sowing grains in the field. Under conditions of water stress, Jatropha mulch significantly maintained the soil moisture content necessary for normal plant growth.

RESULTS

We noted a decrease in plant height, shoot and root fresh/dry weight, leaf area, leaf relative water content (LRWC), chlorophyll, and carotenoid content due to water stress. However, water stress caused an increase in leaf and root phenolics content, leaf soluble sugars and electrolytes leakage. We observed that Jatropha mulch maintained LRWC, plant height, shoot and root fresh/dry weight, leaf area and chlorophyll content under water stress. Moreover, water stress adverse effects on leaf soluble sugar content and electrolyte leakage were reversed to normal by Jatropha mulch.

CONCLUSION

Therefore, it may be concluded that Jatropha leaves mulch will minimize water stress adverse effects on wheat by maintaining soil moisture and plant water status.

Harnessing digital technology to improve agricultural productivity?

Can improving access to mobile extension improve agricultural productivity? Recent evidence suggests both significant and insignificant ways in which SMS-based agricultural information could affect farming outcomes. It is unclear if variations in the programs' design or the methodological challenges in evaluating the programs cause wide-ranging impacts. Extension hotline services provide rapid, unambiguous information by agricultural experts over the phone, tailored to time- and crop-specific shocks. Using methods from experimental economics, we randomly distributed the hotline number to generate exogenous variation in the access to farming information. We conducted our study among 300 farmers in the South Indian state of Karnataka. Our results show that eliminating informational inefficiencies increases farmers' average yields for a high-stakes pigeon pea crop that faced adverse aggregate shock. The impact on the yield is through the adoption of cost-effective and improved farming practices. However, we do not observe any effect on the crops that were not affected by the shock. Our findings reveal that advisory recommendations customized to time- and crop-specific shocks are associated with a greater impact on agricultural productivity.

Effects of leaf removal on the accumulation of anthocyanins and the expression of anthocyanin biosynthetic genes in Cabernet Sauvignon (Vitis vinifera L.) grapes

BACKGROUND

Anthocyanins, a major flavonoid class, determine the color and quality of wine. Recent research revealed that basal leaf removal can increase the content of these compounds. This study determined the effects of basal leaf removal on the anthocyanin profiles of Cabernet Sauvignon grapes.

RESULTS

The effects of basal leaf removal on anthocyanin composition in Cabernet Sauvignon grapes were investigated over two growing seasons. Leaf removal at 5% veraison (VB6) and at 100% veraison (VC6) was compared with a control. Reducing sugar and total anthocyanin contents in the leaf removal group were significantly higher than in the control group at harvest for both vintages. Leaf removal increased the content of individual anthocyanins and significantly improved the malvidin-3-O-glucoside (Mv-3-glc), peonidin-3-O-glucoside (Pn-3-glc), and malvidin-3-O-(6-acetyl)-glucoside (Mv-3-acglc) content of the VB6 group. At harvest, VB6 treatment increased the transcript abundance of structural and regulator genes in the anthocyanin pathway, especially VvF3'5'H, VvLDOX, and VvDFR.

CONCLUSIONS

Our results suggest that leaf removal at 5% veraison may be useful for improving the anthocyanin content in grapes. © 2020 Society of Chemical Industry.

Optimal potassium management strategy to enhance crop yield and soil potassium fertility under paddy-upland rotation

BACKGROUND

An unbalanced application of potassium (K) fertilizer usually destabilizes crop yield and affects soil K fertility. Developing a sustainable K management strategy requires improvements in crop yield without reducing soil K supply capacity over the long term. A combination of field experiments of K fertilization and straw return using rice (Oryza sativa L.)-oilseed rape (Brassica napus L.) rotation was designed to develop an optimal K management strategy.

RESULTS

The results showed the best strategy to maintain yield was K_G +S (input equivalent K removed by seed treatment and straw return), K_S +K_G (input equivalent K removed by straw and seed) and K_C +S (conventional K fertilization and straw return) treatments, and the yield gap among different treatments expanded with the extension of planting years. There were significant differences present in rice and rape K uptake, although no differences in seed K uptake were observed under different K management strategies. The K balance was approximately maintained under K_G +S and K_S +K_G treatments, and negative K balances were present for K_N (no K application), K_C (conventional fertilization), +S (straw return) and K_S treatments (input equivalent K that removed by straw treatment). A positive balance was observed under K_C +S treatment. Slight changes in soil exchangeable and nonexchangeable K were observed under K_G +S and +S treatments. However, high inputs of K fertilizer prevented the improvement of agronomic efficiency and recovery efficiency of K.

CONCLUSIONS

In summary, the optimal K management strategy was K_G +S, which stabilizes the crop yield, maintains soil K fertility and maximizes K use efficiency. © 2020 Society of Chemical Industry.

Bootstrap simulations for evaluating the model estimation of the extent of cross-pollination in maize at the field-scale level

With the recent advent of genetic engineering, numerous genetically modified (GM) crops have been developed, and field planting has been initiated. In open-environment cultivation, the cross-pollination (CP) of GM crops with wild relatives, conventional crops, and organic crops can occur. This exchange of genetic material results in the gene flow phenomenon. Consequently, studies of gene flow among GM crops have primarily focused on the extent of CP between the pollen source plot and the adjacent recipient field. In the present study, Black Pearl Waxy Corn (a variety of purple glutinous maize) was used to simulate a GM-maize pollen source. The pollen recipient was Tainan No. 23 Corn (a variety of white glutinous maize). The CP rate (%) was calculated according to the xenia effect on kernel color. We assessed the suitability of common empirical models of pollen-mediated gene flow (PMGF) for GM maize, and the field border (FB) effect of the model was considered for small-scale farming systems in Asia. Field-scale data were used to construct an optimal model for maize PMGF in the maize-producing areas of Chiayi County, southern Taiwan (R.O.C). Moreover, each model was verified through simulation and by using the 95% percentile bootstrap confidence interval length. According to the results, a model incorporating both the distance from the source and the FB can have optimal fitting and predictive abilities.

Distinctive in-planta acclimation responses to basal growth and acute heat stress were induced in Arabidopsis by cattle manure biochar

In-planta mechanisms of biochar (BC)-mediated improved growth were evaluated by examining oxidative stress, metabolic, and hormonal changes of Arabidopsis wild-type plants under basal or acute heat stress (-HS/ + HS) conditions with or without BC (+ BC/-BC). The oxidative stress was evaluated by using Arabidopsis expressing redox-sensitive green fluorescent protein in the plastids (pla-roGFP2). Fresh biomass and inflorescence height were greater in + BC(‒HS) plants than in the -BC(‒HS) plants, despite similar leaf nutrient levels, photosystem II (PSII) maximal efficiencies and similar oxidative poise. Endogenous levels of jasmonic and abscisic acids were higher in the + BC(‒HS) treatment, suggesting their role in growth improvement. HS in ‒BC plants caused reductions in inflorescence height and PSII maximum quantum yield, as well as significant oxidative stress symptoms manifested by increased lipid peroxidation, greater chloroplast redox poise (oxidized form of roGFP), increased expression of DNAJ heat shock proteins and Zn-finger genes, and reduced expression of glutathione-S-transferase gene in addition to higher abscisic acid and salicylic acid levels. Oxidative stress symptoms were significantly reduced by BC. Results suggest that growth improvements by BC occurring under basal and HS conditions are induced by acclimation mechanisms to 'microstresses' associated with basal growth and to oxidative stress of HS, respectively.

Regional differences in farmers' preferences for a native bee conservation policy: The case of farming communities in Northern and Eastern Thailand

Evidence points to past bee-mediated crop pollination deficits in Chanthaburi province, Eastern Thailand. Conversely, no such evidence has yet been reported for Chiang Mai province (Northern Thailand), suggesting that wild pollination is delivered there above the requirements of local orchards. Discrete choice experiments (DCE) were conducted to elicit the preferences of pollinator-dependent orchard farmers with regard to three pollinator conservation measures and their possible effects on of native bee populations in each region. We fitted random parameter logit (RPL) models on the resulting data to capture preference heterogeneity and to obtain willingness to pay (WTP) point estimates. To test our results' robustness, we also inspected for scale heterogeneity by fitting generalized mixed logit (GMXL) models on the pooled and individual datasets. This yielded WTP space estimates (i.e., directly from WTP distributions) and made possible the comparison of farmers' preferences for a native bee conservation policy in both regions. The results hint at significant WTP differences for some of the conservation policy attributes between both provinces. Furthermore, unobserved contributions to choice seem to have been more random in Chiang Mai. Our analyses also suggest that farmers who engage in bee-related activities are WTP more for a conservation policy that includes bee husbandry.

Ridge-furrow with grass straw mulching farming system to boost rainfed wheat productivity and water use efficiency in semiarid Kenya

BACKGROUND

Ridge-furrow mulching farming systems (RFMs) aim to increase field productivity and improve water use efficiency. To explore environment-friendly and efficient farming systems is a central aspect of rainfed wheat field management in Kenya where rainfall utilization is at a low level. We introduced RFMs (including plastic film and grass straw mulching) to semiarid Kenya to evaluate the effects on field productivity, rainwater utilization, soil quality and economic profitability using old and modern wheat cultivars from 2012 to 2013.

RESULTS

Across the cultivars, the RFMs increased grain yield, aboveground biomass and water use efficiency by 74-163%, 36-104% and 89-273%, respectively, compared with conventional flat planting (control). RFMs significantly shortened the vegetative period while prolonging the reproductive period. The net economic output under RFMs was 74-165% higher than that of the control. Grass straw mulching achieved the highest economic output to input ratio, almost 45% higher than plastic film mulching, despite the former harvested only 82% of the maximum field productivity of the latter. Compared with the control, grass straw mulching promoted the contents of soil organic carbon, total nitrogen and C:N ratio by 14%, 8% and 5%, respectively, while obviously decreased values of these parameters were observed under plastic mulching.

CONCLUSIONS

Through reducing soil water loss, and improving rainwater use efficiency and soil quality, ridge-furrow grass straw mulching would be a sustainable option for boosting field productivity and thus ensuring local food security in rainfed agricultural areas of Kenya. © 2020 Society of Chemical Industry.

Optimum Olsen Phosphorus/ZincDTPA ratio for the initial growth of maize in agricultural soils of the Mediterranean region

BACKGROUND

Zinc (Zn) deficiency in crops is commonly aggravated by high levels of phosphorus (P) in soil. In this work, the initial performance of pot-growing maize in response to the available P and Zn in soils with low available Zn and to the application of P and Zn fertilizers was investigated.

RESULTS

The soils (six non-calcareous and 14 calcareous) ranged widely in available P (Olsen P: 5.5-37.9 mg kg^-1 ), were poor in available Zn [diethylenetriaminepentaacetic acid-extractable Zn (Zn_DTPA ): 0.20-0.84 mg kg^-1 ] and had an Olsen P/Zn_DTPA ratio of 13 to 111 mg mg^-1 . Soil P application generally increased aerial dry matter (ADM) yield; Zn increased ADM yield mostly when applied in combination with P; and the sole application of Zn increased yield only in a soil with a high (28 mg kg^-1 ) Olsen P and a low (0.36 mg kg^-1 ) Zn_DTPA . The increase in ADM yield resulting from optimal application of P and/or Zn to the soil was modest in soils where the Olsen P/Zn_DTPA ratio was 30-60 and Olsen P was >14 mg kg^-1 . Zinc uptake by the control plants was correlated with the Zn_DTPA of the soil. For a certain Zn_DTPA value, the level of plant available Zn was higher in non-calcareous than in calcareous soils.

CONCLUSION

Soil application of fertilizer P and Zn, in soils with low levels of available Zn, should not only aim at increasing the available P and Zn levels but also balancing them at the appropriate Olsen P/Zn_DTPA ratio, which was found to lie in the 30-60 range in the present study. © 2020 Society of Chemical Industry.

CRISPR-Cas-mediated chromosome engineering for crop improvement and synthetic biology

Plant breeding relies on the presence of genetic variation, as well as on the ability to break or stabilize genetic linkages between traits. The development of the genome-editing tool clustered regularly interspaced short palindromic repeats (CRISPR)-CRISPR-associated protein (Cas) has allowed breeders to induce genetic variability in a controlled and site-specific manner, and to improve traits with high efficiency. However, the presence of genetic linkages is a major obstacle to the transfer of desirable traits from wild species to their cultivated relatives. One way to address this issue is to create mutants with deficiencies in the meiotic recombination machinery, thereby enhancing global crossover frequencies between homologous parental chromosomes. Although this seemed to be a promising approach at first, thus far, no crossover frequencies could be enhanced in recombination-cold regions of the genome. Additionally, this approach can lead to unintended genomic instabilities due to DNA repair defects. Therefore, efforts have been undertaken to obtain predefined crossovers between homologues by inducing site-specific double-strand breaks (DSBs) in meiotic, as well as in somatic plant cells using CRISPR-Cas tools. However, this strategy has not been able to produce a substantial number of heritable homologous recombination-based crossovers. Most recently, heritable chromosomal rearrangements, such as inversions and translocations, have been obtained in a controlled way using CRISPR-Cas in plants. This approach unlocks a completely new way of manipulating genetic linkages, one in which the DSBs are induced in somatic cells, enabling the formation of chromosomal rearrangements in the megabase range, by DSB repair via non-homologous end-joining. This technology might also enable the restructuring of genomes more globally, resulting in not only the obtainment of synthetic plant chromosome, but also of novel plant species.

The estimation of non-irrigated crop area and production using the regression analysis approach: A case study of Bursa Region (Turkey) in the mid-nineteenth century

Agricultural land cover and its changing extent are directly related to human activities, which have an adverse impact on the environment and ecosystems. The historical knowledge of crop production and its cultivation area is a key element. Such data provide a base for monitoring and mapping spatio-temporal changes in agricultural land cover/use, which is of great significance to examine its impacts on environmental systems. Historical maps and related data obtained from historical archives can be effectively used for reconstruction purposes through using sample data from ground observations, government inventories, or other historical sources. This study considered historical population and cropland survey data obtained from Ottoman Archives and cropland suitability map, accessibility, and geophysical attributes as ancillary data to estimate non-irrigated crop production and its corresponding cultivation area in the 1840s Bursa Region, Turkey. We used the regression analysis approach to estimate agricultural land area and grain production for the unknown data points in the study region. We provide the spatial distribution of production and its cultivation area based on the estimates of regression models. The reconstruction can be used in line with future historical research aiming to model landscape, climate, and ecosystems to assess the impact of human activities on the environmental systems in preindustrial times in the Bursa Region context.

Sucrose Utilization for Improved Crop Yields: A Review Article

Photosynthetic carbon converted to sucrose is vital for plant growth. Sucrose acts as a signaling molecule and a primary energy source that coordinates the source and sink development. Alteration in source-sink balance halts the physiological and developmental processes of plants, since plant growth is mostly triggered when the primary assimilates in the source leaf balance with the metabolic needs of the heterotrophic sinks. To measure up with the sink organ's metabolic needs, the improvement of photosynthetic carbon to synthesis sucrose, its remobilization, and utilization at the sink level becomes imperative. However, environmental cues that influence sucrose balance within these plant organs, limiting positive yield prospects, have also been a rising issue over the past few decades. Thus, this review discusses strategies to improve photosynthetic carbon assimilation, the pathways actively involved in the transport of sucrose from source to sink organs, and their utilization at the sink organ. We further emphasize the impact of various environmental cues on sucrose transport and utilization, and the strategic yield improvement approaches under such conditions.