Abstract

1. Introduction

2. Fundamentals of nanotechnology

3. The role of nanotechnology in achieving food security

4. Nanotubes in food and agriculture

5. Nanosensors in food and agriculture

6. The challenges of nanotechnology in food and agriculture system

7. Conclusions

References

Abstract

     Ensuring food security in developing countries is highly challenging due to low productivity of the agriculture sector, degradation of natural resources, high post farming losses, less or no value addition, and high population growth. Researchers are striving to adopt newer technologies to enhance supply to narrow the food demand gap. Nanotechnology is one of the promising technologies that could improve agricultural productivity via nano fertilizers, use of efficient herbicides and pesticides, soil feature regulation, wastewater management, and pathogen detection. It is equally beneficial for industrial food processing with enhanced food production with excellent market value, elevated nutritional and sensing property, improved safety, and better antimicrobial protection. Nanotechnology can also reduce post-farming losses by increasing the shelf life with the aid of nanoparticles. However, further investigation is required to solve the safety and health risks associated with the technology.

Introduction

     The foremost universal challenge on our planet is the question of establishing food security for a rapidly increasing population in the world. Predictions show that food demand is likely to rise from 59 to 98% for the world population reaching 9 billion by 2050 (Duro et al., 2020). Despite an increase of the world population particularly in developing countries, the global food supply interrupted by the expenditure of bio-resources for production of energy, manufacturing chemicals, high post farming loss, less value addition, inefficient distribution and marketing systems, and other factors (Barrett, 2021; Sekhon, 2014). Farmers throughout the world will focus on using new innovations and technologies for enhancing the production of crops through intensive and extensive agriculture. The current efforts further boosted through the use of nano-modified stimulants and precision farming. Agricultural efficiency, soil improvement, secure water use, distribution of food in stores, and its quality are basic factors of securing food that may be improved via advances in nanotechnology research (Ashraf et al., 2021; Sastry et al., 2011).

     Newer technology that will increase the production and reduce food wastage is important to maintain sustainable living standards of the nation and improve food security. Nanotechnology can provide a path for producing foods with outstanding quality in highly improved workable form along with induction of nutrients bioavailability. Many research investigations are focusing on increasing the application of nanotechnology for the production of crop and food processing (Abobatta, 2018; Axelos and Van De Voorde, 2017; Dasgupta et al., 2015; Peters et al., 2016). Increment in articles, intellectual property, and patents in nano-agriculture-based food with fresh research tendencies in the processing of food, nutraceutical distribution, packing, quality control, and serviceable food is a highly expanding field in nanotechnology research (Dasgupta et al., 2015).

Conclusions

     Nanotechnology is a newly emerging, but highly expanding technology in many fields related to human activities and benefits worldwide. Its fascinating phenomena have been witnessed through several research findings that the nanoparticles and nanostructure improve various properties due to small size, larger surface area, and highly catalytic nature. Nanotechnology is crucial in achieving food security, especially in the agriculture sector. It can improve crop production by effective microbial, pest, and weed control with high economic value, security, and safety. It also plays a key role in food processing, food modification, stability, sensing, prolonged shelf life, minimized food losses, and provide safe food. Nanotechnology also minimizes post-harvest losses with better stability, safety, and packaging materials. Nanoparticles like Ag, Au, Zn, TiO2, ZnO, SiO2, and MgO commonly used in food processing, may also induce health risks due to easy penetration through the cell for adverse reactions within various humans, and animal organs as well as parts of plants. Such risks due to nanoparticles or nanocomposite could be controlled in future research via using greener synthesis and searching for easy and cheaper protocols for degradation and removal of existing nanomaterial from the sites of attack.

The excessive use of chemical fertilizers in conventional agricultural systems decreased the nutrient use efficiency and caused serious environmental problems such as waterway pollution, mineral depletion, soil acidification and other issues. In order to achieve the desirable essential oil productivity and reduction consumption of chemical inputs in peppermint (Mentha x piperita L.), a 2-year field experiment was carried out using a splitplot approach based on a randomized complete block design (RCBD), with 7 treatments and three replications at two harvesting times. The main factor was given by different fertilizer treatments including no fertilizer (control), chemical fertilizer, arbuscular mycorrhiza fungus, 50 % chemical fertilizer + arbuscular mycorrhiza fungus, nano chelated fertilizer, 50 % chemical fertilizer + nano chelated fertilizer, nano chelated fertilizer + arbuscular mycorrhiza fungus, and the sub-factor included two harvesting times (first harvest and second harvest). The results demonstrated that the highest and lowest growth parameters including plant height, number of lateral branches per plant and leaf greenness (SPAD index) were achieved with integrative application of 50 % chemical fertilizer + nano chelated fertilizer (in the first harvest) and control conditions (in the second harvest), respectively. Also, the maximum concentration of N, P, K and Fe was reached in the first harvest with application of 50 % chemical fertilizer + nano chelated fertilizer. Furthermore, the highest peppermint dry matter yield (354.8 g/m2 ), essential oil content (2.7 %) and essential oil yield (6.6 g/m2 ) was achieved at the first harvest with application of 50 % chemical fertilizer + nano chelated fertilizer. GC–MS analysis of peppermint essential oil showed that the major components at first harvest were menthol (31.82–37.87 %), menthone (23.85–30.90 %), 1,8-cineole (6.39–6.82 %), δ-terpineol (3.61–4.11 %) and neo-menthol (2.67–3.33 %), whereas at second harvest menthol (44–47.31 %), p-menth-L-en-9-ol (11.66–14.96 %), menthofuran (3.44–5.14 %), menthone (3.82–10.62 %), 1,8-cineole (5.51–5.99 %) and neo-menthol (5.03–5.90 %). Notably, menthol reached the highest amount with application of 50 % chemical fertilizer + nano chelated fertilizer. Overall, an integrative application of chemical fertilizers with nano fertilizers can be suggested to farmers as an alternative and environmentally friendly strategy to improve the quali-quantitative characteristics of peppermint essential oil.

Introduction

Nowadays, the rapid thrive of global population increased the requirements for food and energy, leading to the enhancement of agricultural productivity in regions with limited cultivation area (Liu and Lal, 2015; Chen and Yada, 2011). In the conventional agricultural systems, the excessive use of chemical inputs allowed to increase the agricultural productivity. Detrimental implications on the environment and human health from intensive agricultural practices and long-term use of chemical fertilizers have been well evidenced (Bansal, 2017). Intensive application of chemical fertilizers has di fferent negative impacts on environment including the aggregation of pesticides and fertilizers, soil erosion, soil and water pollution, genetic erosion, leaching of nutrients and reduction of agrobiodiversity (Daneshmandi and Seyyedi, 2019). The soil health management is crucial for ensuring ecological and agricultural productions and maintaining plant diversity. The negative impacts of chemical fertilizers forced the agrochemical companies to replace them with biofertilizers in sustainable agricultural systems in order to achieve a desirable crop productivity (Sharma et al., 2013). Over 80 % of plant species like those belonging to Fabaceae (Weisany et al., 2016), Asteraceae (Kapoor et al., 2007), Apiaceae (Kapoor et al., 2002) and Lamiaceae (Tarraf et al., 2017) establish mutualistic associations with arbuscular mycorrhiza (AM) fungi.

The habituation of cultured cells to cellulose biosynthesis inhibitors such as dichlobenil (dichlorobenzonitrile, DCB) has proven a valuable tool to elucidate the mechanisms involved in plant cell wall structural plasticity. Our group has demonstrated that maize cells cope with DCB through a modified cell wall in which cellulose is replaced by a more extensive network of highly cross-linked feruloylated arabinoxylans. In order to gain further insight into the contribution of phenolics to the early remodelling of cellulose-deficient cell walls, a comparative HPLC-PAD analysis was carried out of hydroxycinnamates esterified into nascent and cell wall polysaccharides obtained from non-habituated (NH) and habituated to low DCB concentrations (1.5 μM; H) maize suspensioncultured cells. Incipient DCB-habituated cell walls showed significantly higher levels of esterified ferulic acid and p-coumaric acid throughout the culture cycle. In terms of cell wall fortification, ferulic acid is associated to arabinoxylan crosslinking whereas the increase of p-coumaric suggests an early lignification response. As expected, the level of hydroxycinnamates esterified into nascent polysaccharides was also higher in DCB-habituated cells indicating an overexpression of phenylpropanoid pathway. Due to their key role in cell wall strengthening, special attention was paid into the dimerization pattern of ferulic acid. A quantitative comparison of diferulate dehydrodimers (DFAs) between cell lines and cell compartments revealed that an extra dimerization took place in H cells when both nascent and mature cell wall polysaccharides were analysed. In addition, qualitative differences in the ferulic acid coupling pattern were detected in H cells, allowing us to suggest that 8-O-4′-DFA and 8-5′-DFA featured the ferulic acid dimerization when it occurred in the protoplasmic and cell wall fractions respectively. Both qualitative and quantitative differences in the phenolic profile between NH and H cells point to a regioselectivity in the ferulate dehydrodimerization.

Introduction

Primary cell walls of commelinoid monocots (also known as type II cell walls) such as maize are composed of a framework of cellulose microfibrils embedded in a hemicellulosic matrix of (glucurono)arabinoxylans and a smaller amount of pectins and glycoproteins (Carpita and Gibeaut, 1993). These cell walls are also characterised by the presence of cell wall phenolics, mainly the hydroxycinnamates, ferulic (FA) and p-coumaric (CA) acids, which are ester-linked to α–L-arabinosyl residues of (glucurono)arabinoxylans (Smith and Hartley, 1983; Wende and Fry, 1997). Although phenolics are minor components of the primary cell wall (~1% of cell wall dry weight), their contribution to cell wall assembly seems to be crucial. In vitro experiments have demonstrated that hydroxycinnamates are susceptible to oxidative coupling in the presence of peroxidases and hydrogen peroxide, cross-linking adjacent arabinoxylan (AX) molecules and thus contributing to cell wall assembly (Geissman and Neukom, 1971; Fry et al., 2000; Fry, 2004; Encina and Fry, 2005; Parker et al., 2005; Burr and Fry, 2009). Due to its polysaccharide cross-linking role, phenolic coupling is involved in a number of cell wall properties, causing cell wall stiffening and growth cessation, promoting tissue cohesion, strengthening cell wall structure in response to biotic and abiotic stresses and hindering cell wall degradability (de O Buanafina, 2009).

Limited non-farm opportunities in the rural areas of the developing world, coupled with population growth, means agriculture will continue to play a dominant role as a source of livelihood in these areas. Thus, while rural transformation has dominated recent literature as a way of improving welfare through diversifying into non-farm sectors, improving productivity and resilience to shocks in smallholder agricultural production cannot be downplayed. This is especially so given the changing climatic conditions affecting agricultural production, and thus threatening many livelihoods in rural areas. Farm diversification is an important strategy for creating resilience against climatic shocks in farm production. Using cross-sectional data from northern Namibia, the study assesses the barriers and success factors related to effective crop and livestock enterprises diversification and the effect of these on food security outcomes. A Seemingly Unrelated Regression model is used to assess the joint factors explaining total farm diversification, while a step-wise error correction model is used to evaluate the conditional effect of diversification in each of the two farm enterprises on two measures of food security: food expenditure and dietary diversity. We find that past exposure to climate shocks informs current diversification levels and that access to climate information is a key success factor for both livestock and crop diversification. In terms of food security, greater diversification in either crop or livestock production leads to higher food security outcomes, with neither crop nor livestock diversification showing dominance in affecting food security outcomes. However, an overall higher level of diversification in both livestock and crop enterprises is dominant in explaining food security outcomes.

Introduction

Risk is inherent in small-scale rain-fed agricultural production. Farmers have to contend with seasonal weather uncertainties, the threat of pests and diseases, and post-harvest losses, among other risks. These risks are being exacerbated by the effects of a changing climate; for example, the severity and distribution of important livestock and crop diseases is changing, while incidents of droughts and floods are on the rise (Elad & Pertot, 2014; Thornton, van de Steeg, Notenbaert, & Herrero, 2009; Wetherald & Manabe, 2002). These effects of climate change are expected to increase poverty incidences in most developing countries and create new poverty pockets in countries with increasing inequality (IPCC, 2014). Agricultural production has been stagnant in Sub-Saharan Africa (SSA), and there is consensus that the current trend in productivity cannot guarantee food security in the region (Jayne, Chamberlin, & Headey, 2014; Kyalo Willy, Muyanga, & Jayne, 2019; Onyutha, 2018). Climatic shocks that further adversely affect food production are a serious threat to food security and livelihoods in the region. While there are adaptation options that can create resilience in agricultural productivity, studies continue to show low adoption rates across the region (Bradshaw, Dolan, & Smit, 2004; Di Falco, Veronesi, & Yesuf, 2011; Mulwa, Marenya, Rahut, & Kassie, 2017; Singh et al., 2017; Smit & Wandel, 2006). In crop farming, such adaptation measures include using seeds adapted to climate-stressors (for example drought resistant seeds) and spreading risks across different crop types (Howden et al., 2007).

Key Features of Pollen Germination in Cereals

Genetic and Proteomic Screening for Key Factors in Pollen Germination

Key Pathways Identified for Pollen Germination in Cereals

Concluding Remarks

References

Germination of Pollen

In flowering plants, the distribution of pollen (see Glossary) across land by wind and/or animals drives the spread of genetic variation within a species. Agriculturally, successful fertilization of flowers in an increasingly harsh and unpredictable climate is the key determinant of grain production and yield in cereal crops [1]. Mature pollen usually contains only two cell types – sperm cells and the much larger vegetative (or tube) cell – and desiccates before release from the anther. On adhering to a compatible stigma, pollen grains respond to signals from the mother plant and become active, undergoing cytoplasmic reorganization and activation of stored RNA and protein to produce a pollen tube originating from the vegetative cell. The pollen tube elongates within the pistil until it reaches the egg cell, where the sperm cell divides to enable the double-fertilization event typical of plants (Figure 1, Key Figure).
The factors that control successful pollen germination have been the focus of plant reproduction, evolution, and breeding research to increase crop yield and to overcome hybridization barriers [1,2]. Barriers to fertilization include interspecific incompatibility as well as self-incompatibility, which maintains genetic diversity within a local population. However, overcoming some of these constraints in a breeding environment can contribute to the production of novel elite lines for specific end-uses. Since 2003, pollen transcriptomic studies, together with identified mutants, have rapidly expanded our knowledge of the regulatory mechanisms that govern the fertilization process, including signaling pathways and cytoskeleton proteins [3–11]. However, most of this research has occurred in model plant species such as arabidopsis; despite massive agronomic and economic interest, relatively little is known about these molecular processes in cereal crops (the Poaceae). This review focuses on the unique characteristics of pollen grain adhesion, hydration, germination, and pollen tube growth in monocot cereals, and provides an overview of our current understanding of the regulators governed by the male gametophyte in the best-studied species, rice (Oryza sativa) and maize (Zea mays) (Figure 1C).

In recent years, forest breeding programs have increased Eucalyptus production for commercial purposes; however, high-performing Eucalyptus clones have had problems with propagation, especially when rooting. Nevertheless, studies have shown that inoculation of microorganisms producing indole-3- acetic acid (IAA) is an especially productive procedure to help these clones breed. In this study, we evaluated the production of IAA and analogues in 16 microbial strains. For the first time, a high IAA production was described in the strain Aspergillus flavipes (ATCC® 16814™), and A. flavipes was shown by LC-MS/MS to produce IAA through a tryptophan-dependent biosynthetic pathway. A. flavipes reached the highest IAA production when cultivated under solid-state fermentation in an optimized medium composed of soybean bran, water and tryptophan. We mixed the fermentation products in solid form (SF) and liquid form (LF) with the substrate Carolina I® and then planted the cuttings of the hybrid Eucalyptus grandis x E. urophylla (clone IPB2). In fact, treatments with 40e120 mg kg
1 of SF increased the adventitious rooting rate, root length and both root fresh and dry mass, while 120 mg kg
1 of LF increased root length and dry mass. Additionally, there was no toxicity on fibroblasts (NIH/3t3), and, therefore, the plant biostimulant was confirmed as a novel, non-toxic, and eco-friendly solution.

Introduction

Clonal plantation of Eucalyptus based on vegetative propagation is successful mainly due to well-developed forest breeding programs. However, vegetative propagation efficiency is prejudiced in some species due to specific endogenous and exogenous factors of the mother plant, alterations of the root system architecture and topophysis effects that influence the rooting potential (Peralta et al., 2012). The clone IPB2 of the hybrid Eucalyptus grandis x Eucalyptus urophylla from ArborGen is classified as a clone SuperTree®. Such clones are selected for a higher volume of wood, disease resistance, trunk straightness, and wood quality characteristics (ArborGen, 2018). Despite the advantages in the field, the clone has difficulties in rooting, demanding research to promote the adventitious roots induction and development. The inoculation of some classes of microorganisms can assist in overcoming this difficulty, stimulating adventitious root growth, increasing the absorption of nutrients and water, the host-plant biomass and the tolerance to stresses such as drought and diseases (Sukumar et al., 2013). When a substance can improve the plant nutritional efficiency and abiotic stress and/or influence the quality of the crop, regardless of its nutritional status, it is denominated as a plant biostimulant (du Jardin, 2015). The commercial products are currently divided into five classes: microbial inoculants, humic acids, fulvic acids, amino acids and seaweed extracts (Calvo et al., 2014). The commercial biostimulants can contain one or more microorganisms and/or substances (du Jardin, 2015).

Increased biodiversity can make valuable contributions to food production and security around the world. The role of plant species diversity for “ecological intensification” of agriculture has been widely recognised, but the potential contribution of multi-trophic-level production systems, such as rice-fish coculture, has received less attention. A continuous 4-year experiment (2015e2018) was conducted comparing rice-fish (yellow finless eel and loach) co-culture, and mono-rice planting practices on the Chongming Eco-island of China. During the experiment, pests (insect herbivores and weeds), arthropods, pesticides, grain and marketable fish yield were sampled, soil quality (available nitrogen, phosphorus and potassium, total nitrogen, organic matter content and pH) and rice grain quality (protein content, chalkiness, gel consistency, amylose content) were evaluated, and an economic analysis were performed. Fish decreased herbivore insect abundance by 24.07%, reduced weeds abundance, richness and biomass by 67.62, 62.01 and 58.88% respectively, increased invertebrate predator abundance by 19.48%, and reduced the need for pesticide by 23.4%. Co-culture practice produced an average economic values 10.33% higher than in the mono-rice farming. In addition, rice-fish co-culture enhanced both soil and rice quality. Our results confirm that rice-fish co-culture can be an effective form of ecological intensification, incorporating and contributing ecosystem services in agricultural production and increasing sustainability.

Introduction

Agricultural intensification has been recognised one of the main reasons for biodiversity loss and related decline in ecosystem functioning due to the conversion of natural habitats into monoculture farming areas (Gagic et al., 2012; Batary et al., 2017 ; Hass et al., 2018; Plue et al., 2018). Intensive use of agrochemicals is reducing environmental quality (Stehle and Schulz, 2015; He et al., 2017; Ruiz and MarAa Dolores, 2018 ~ ), damaging local plant communities (Cassman, 1999; Kremen et al., 2012), and reducing the abundance and richness of beneficial arthropods (Gagic et al., 2012; Kovacs-Hosty anszki et al., 2017 ). The concept of “ecological intensification” has been promoted to redesign agroecosystems, based on the increased use of ecological processes and biodiversity, using resource more efficiently, and decreasing anthropogenic inputs (Bommarco et al., 2013; Pywell et al., 2015; Bowles et al., 2016). In this framework, it has been showed that plant-diversified farming practices can contribute to ecological intensification of agriculture by providing multiple ecosystem services, promoting biological pest control (Redlich et al., 2018; Wan et al., 2018), decreasing the use of pesticides (Tscharntke et al., 2005; Gurr et al., 2016; Zhao et al., 2016), improving soil quality (Cassman, 1999), and enhancing crop yields (Tittonell and Giller., 2013; Gurr et al., 2016). The potential contribution of multi-trophic-level production systems, such as rice-fish co-culture, to ecological intensification has not received as much attention.

Appropriate tillage practices reduce a crop’s carbon footprint (CF) and mitigate climate change. However, little is known about the CF of winter wheat and spring maize production under different tillage practices in the Loess Plateau of China. To quantify the tillage differences and crop type differences in CF, a field experiment was established in 2007 in which the following six tillage practices were evaluated: plow tillage (PT), no-tillage (NT), subsoil tillage (ST), PT/NT rotation, NT/ST rotation and ST/PT rotation. The results showed PT had the positive CF value (488 kg CO2-eq ha
1 ), indicating a carbon source. However, NT, ST, ST/PT, PT/NT and NT/ST significantly decreased the CF (
628,
1382,
2328,
3038 and
3545 kg CO2-eq ha
1 ), demonstrating these tillage practices served as carbon sinks. The functional unit-scaled CFs (yield-scaled CF, cost-scaled CF, production value-scaled CF and net income-scaled CF) were similar to the trend of CF, which exhibited the following order: NT/ST > PT/NT > ST/PT > ST > NT > PT. The CF and functional unit-scaled CFs of winter wheat production were significantly higher than those of spring maize production. The CF and functional unit-scaled CFs decreased as planting year increased. In addition, increasing SOC storage and grain yield were benefit for decreasing CF. The results of this study showed NT/ST rotation produced the highest grain yield and SOC storage with the lowest CF and functional unit-scaled CFs and was thus determined to be the best tillage practice for balancing sustainable production with the environment in the Loess Plateau.

Introduction

Climate change is a global issue. Greenhouse gases (GHGs) from human activities are continuously emitted into the atmosphere from industrialization, energy and agricultural activities (Linquist et al., 2012). Globally, agricultural activity-produced total non-CO2 GHG emissions comprised 10e12% of the anthropogenic emissions recorded in 2010 (Edenhofer et al., 2014). In China, GHG emissions from agricultural activities were 0.94 Gt CO2-eq$yr
1 in 2012 (NDRC, 2016). Therefore, promoting cleaner production technology with less GHG emissions is necessary to mitigate global climate change and realize sustainable agricultural development. Carbon footprint (CF) is used to effectively evaluate the GHG emissions of a product (BSI, 2011) and have been used recently as a robust research approach to study climate change phenomena. Pishgar-Komleh et al. (2017) quantified the CF variability of tomato production in two farms in Iran. Ali et al. (2017) estimated the effect of 12 management practices on CF in Italy. Yang et al. (2014) compared the CF of five cropping systems in the North China Plain. These studies aimed to attain proper measures for reducing GHG emissions in the local crop production by comparing CF. In addition, different CF have been observed in major grain crops production. Previous studies have reported the CF of wheat production was higher than that of maize production (Huang et al., 2017; Yan et al., 2015).

Meeting the challenge of feeding a growing population with limited resources will require increasing the yield potential of staple crops, such as rice. Yet many high-yielding, intensive production systems have experienced slow rates of yield improvement in recent years despite a demonstrated increase in the yield potential of new crop cultivars. We analyzed experimental data from one such cropping system, i.e., California (CA) rice, in order to quantify improvements made in the genetic yield potential obtained through plant breeding. California rice systems are among the highest in the world and close to maximum yield potential. Specifically, the hypothesis was tested that if rice cultivar yields decline over time then apparent yield increases in side-by-side yield comparison tests will not reflect increases in yield potential. This hypothesis was tested using 33 years of experimental yield data from the California Cooperative Rice Research Foundation Rice Experiment Station. Based on side-by-side comparisons of old and new rice cultivars which do not consider yield decline over time, there was an apparent increase in yield. However, the yields of older cultivars were found to decline at an estimated rate of 29.3 kg ha−1 year−1 (90% credible interval −4.4 to −53.3) after initial selection. Once this effect was considered, the yield advantage of newer cultivars over old was uncertain (−3.3 kg ha−1 year−1 , 90% credible interval −36.1 to 31.5). These results highlight (1) the importance of continuous crop improvement and deployment of new cultivars simply to maintain existing yields, and (2) to increase the genetic yield potential, higher yield targets are needed. Importantly, when breeding near the yield potential, despite the limited yield gains, significant advances in improving quality and reducing crop duration have been made.

Introduction

Constraints on arable land are increasing simultaneous with the need to increase total food production to meet a growing demand (Foley et al., 2011; Godfray et al., 2010; Mueller et al., 2012), which has necessitated harvesting more grain per unit land area (Lobell et al., 2009; Tittonell, 2014). Historically, agricultural research has been successful in staving off the “Malthusian catastrophe” of demand surpassing supply via continued yield improvement of staple crops. However, many production systems are experiencing plateaus in grain yield (Grassini et al., 2013). If this trend continues, improvements per unit land area are no longer possible, and an increase in the area under cultivation will be needed to meet food demand, which carries undesirable ecological implications (Foley et al., 2011; Tilman et al., 2011). Therefore, it is of critical importance to better understand why the rate of increase in grain yields has declined or leveled off in intensified production systems. California (CA) rice represents one such production system. Rice is grown primarily in the Sacramento Valley, which is characterized by having a Mediterranean climate with long days, a dry growing season relatively free of pests and diseases. These conditions lead to some of the highest yields in the world FAOSTAT, 2016. Production in CA is predominately focused on premium quality medium grain japonica cultivars (e.g., CalRose rice), and rice from CA is recognized globally for its quality (http://agfax.com/2015/11/03/rice-calrose-wins-best-riceworld-competition/). Most cultivars in use in CA are developed by the California Cooperative Rice Research Foundation (CCRRF; a collaboration between the University of California, the USDA-Agricultural Research Service, and farmer-funded research). In part due to improvements in rice genetics, rice yields in CA increased rapidly during the period from 1920 to 1990; however, since the 1990s, the rate of yield increase has slowed (Fig. S2) despite continuous crop improvement. Based on a yield-gap analysis, on-farm yields in the major rice growing region of CA is 73–76% of maximum yield potential (Espe et al., 2016). In highly intensive systems such as this, Grassini et al. (2011) have shown that farmers are capable of attaining 85% of the maximum yield potential. Thus, given that farmers are near the attainable yield potential, increases in yield are likely to be relatively slow and Espe et al. (2016) reported that indeed this was the case with yields on average increasing by about 50–62 kg ha−1 year−1 between 1999 and 2014. Certainly one question in looking at this situation is, “do new cultivars have greater yield potential”?

abstract

The ‘Plantain-Optim’ dataset (came from the ‘Plantain-Optim’ experiment conducted from 2009 to 2011 at CARBAP experimental station in Cameroon. The main objective was to describe agronomic potential of nine plantain varieties, including five natural plantains commonly cropped in Cameroon, and four plantain-like hybrids. A completely randomized bloc permitted to compare growth, development and yield of 45 plants per variety split between five replicates. Cropping practices guarantied non-limiting and homogenous conditions. Each plant was measured every 15 days. Data described aerial organ sizes, foliar structure and bunch characteristics of the mother plant. The ‘Plantain-Optim’ dataset includes the complete individual growth of each studied plantain of the ‘Plantain-Optim’ experiment with a 15-day accuracy. It is a useful standard of plantain varietal diversity for comparison with others datasets. Varietal growth and development homogeneity, biomass production or foliar and bunch structures could be further investigated. Moreover, these accurate data on plantain growth could be valuable for plantain 3D modelling.

1. Data

1.1. Background

Plantain is one of the most important staple food in West and Central Africa. Like others Musa species, plantain (Musa acuminata × Musa balbisiana) is a giant monocotyledon [1] with an underground corm that supports leaves. Leaf sheaths form the pseudostem. A terminal bud leads the inflorescence, and then the bunch, that is compound by hands of bananas. Bananas are called “fingers”. Farmers commonly cropped a large varietal diversity in West and Central Africa. At this time, varietal explorations led more than 135 plantain varieties, which are preserved in the collection of CARBAP (African Centre for Banana and Plantain Researches) experimental station. This diversity represents a large panel of morphologic traits, which are basis of the existing botanical classification into fours subgroups (French, French horn, False horn and True horn) and three plant sizes (‘small’, ‘medium’ and ‘giant’) [2,3]. Hypothesis is that this diversity also represents agronomic potential variations. Alongside this botanical knowledge, very few studies explored agronomic differences between plantain varieties, as yield potential, nutrient and water needs or pest and disease sensitivity. Thus, there is a real lack of knowledge and data concerning agronomic potential to benchmark varieties for farmers [4], even more to choose the best suitable varieties for integrating into innovative and sustainable plantain-based cropping systems. The ‘Plantain-Optim’ experiment aimed to produce scientific data to contribute to this basic knowledge. The ‘Plantain-Optim’ experiment was designed to evaluate and compare yield potential that we assumed to consider as the primary criteria for defining agronomic potential. A board of plantain researchers from CARBAP contributed to identify a panel of commonly cropped and promising varieties in Cameroon, according to future challenges for plantain-based cropping systems. They selected nine varieties, including five natural commonly cropped plantains in Cameroon and four plantain-like hybrids (Table 1). Experimental design was a completely randomized bloc (Fig. 1). The single factor was the variety, with the nine selected varieties as modalities.

Productivity of intensive rice cropping systems plays a pivotal role in national food security in China. By 2030, a 20% increase in rice yield will be required to meet the growing demand for food that will result from population growth. The success of China’s super hybrid rice was expected to provide an opportunity to cope with the increased demand for rice. However, in China the planting area of super hybrid rice is less than 8% of the national total rice planting area and the planting area of hybrid rice has continued to decline since 1996. The decreased planting area of hybrid rice is related to the shift in rice establishment methods from manual transplanting to direct seeding and mechanical transplanting. These shifts can result in increased seeding rates and reduced morphological advantages of heterosis (e.g. reduced panicle size), both of which can influence cultivar choice by rice farmers, who will tend to favor cheaper inbred cultivars. The shifts in rice establishment methods can also eliminate or reduce the seedling nursey period and subsequently shorten the growth duration and negatively affect the yield. We anticipate that the above problems will be resolved by integrating mechanization (e.g. designing high-precision seed sowing machines) with agronomy (e.g. improving management practices for increasing seed vigor) and breeding (e.g. developing high-yielding cultivars with short growth durations). This strategy also has implications for production of other crops in intensive farming systems in China and for other developing countries with rice-based intensive cropping systems.

Challenges to rice production for ensuring food security in China

China has 22% of the world’s population but only 7% of the world’s arable land (Piao et al., 2010). In order to produce enough food, intensive cropping systems have been extensively developed in China. Considerable progress has been made by developing high-yielding crop cultivars and improving crop management practices. As a result, there has been remarkable growth in both crop production and national food security in China (Fan et al., 2012). Rice is a staple food for more than 65% of the population in China. Double-season rice systems and single-season rice in rotation with other crops such as wheat and oilseed rape are the major intensive rice-based cropping systems in China. Over the last 60 years, the production of rice has more than tripled in China mainly due to increased grain yield rather than increased planting area (Fig. 1). However, the population of China continues to grow, and thus domestic production of rice must increase in the next 13 years. It is projected that China needs to produce 41 million t (Mt) more rice by 2030, compared to the 207 Mt produced in 2017 (Fig. 1). Because the area of cropland will decrease with urban expansion (Bren d’Amour et al., 2017), future increases in rice production must come from greater yields. Though the rice planting area will be the same in 2030 as in 2017, an increase in rice yield of 1.36 t ha−1 , or 20%, is required in the next 13 years (Fig. 1). This increase is more than double that (0.60 t ha−1 ) achieved in the last 13 years, presenting a challenge for national food security in China.

Drought is the most important crop production limiting factor in the changing climate scenario and its intensity is predicted to increase in future. Sunflower is an important oilseed crop having 8% share in the world oilseed production. Although, it is a moderately drought tolerant crop, severe drought causes reduction in the seed and oil production. Therefore, to ensure sustainable sunflower achene and oil production, it is very important to understand the relationship among the physiological, biochemical, genetic and agronomic basis of drought for its sustainable management. Impact of drought stress on various aspects of sunflower has been reported earlier but there is not a single study describing the physiological, biochemical and genetic basis of drought in sunflower at molecular and crop level. In this review manuscript, influence of drought on sunflower achene yield and oil quality has been analyzed critically at both cell, plant and crop level, and the possible management options to mitigate the severity of the drought stress are proposed. Available literature describing the impact of drought stress on physiological and biochemical aspects (like, photosynthesis, water relations, nutrient uptake and oxidative damage), morphological and growth parameters and achene yield and oil quality has been discussed critically. Based on the discussion on the impact of drought stress, various management strategies, such as breeding for drought tolerance (conventional or biotechnological), exogenous application of hormones and osmoprotectants, seed treatment and soil nutrient management has been reviewed and discussed. It is concluded from discussion that sunflower responds to water stress by osmotic adjustments, turgor maintenance, carbon assimilation maintenance and hormonal regulations. A comprehensive research on integration of different management options, including agronomic management, conventional breeding and modern biotechnological advances, is needed for the sustainable improvement of sunflower achene yield and oil quality under drought stress. This may also contribute significantly under a climate change scenario.

Introduction

Sunflower (Helianthus annuus L.) is an annual oilseed crop globally cultivated on 24.77 million hectares with a production of 44.31 million metric tons and it has 8% share in world oilseed market (USDA, 2016). Sunflower contains 40–50% oil and 17–20% protein, thus have a fair potential to narrow the gap between production and consumption of edible oil and animal feed in the world. Actually, it is a crop of tropical and subtropical regions with semi-arid to arid climate, and frequently grown in dry lands or on supplementary irrigation. Therefore, the crop is affected by ambient environmental conditions like heat and drought (Pekcan et al., 2015; Robert et al., 2016). However, in a climate change scenario or/and with the onset of early droughts, the crop may be affected by drought stress (Debaeke et al., 2017). In addition to the hiking problem of water stress, the area devoted to irrigated food production systems is expected to decrease resulting in lesser food production (Alexandratos and Bruinsma, 2012; Farooq et al., 2012). Nonetheless, expansion of irrigated land is not possible because of water competition among domestic, industrial and agricultural users (Alexandratos and Bruinsma, 2012). Severe water competition among different users will predominately change the irrigated lands to rain-fed systems and ultimately crops have to suffer from periodic events of drought stress (Elliott et al., 2014). Hence, all of agricultural crops and even the moderately drought tolerant crops such as sunflower will be badly affected by drought stress. Severe drought events have been recorded in Asia and beyond, including the countries with arid and semiarid climates during the last decades (Miyan, 2015; Farooq et al., 2012, 2014), which made management of drought stress more challenging. Although, sunflower is moderately drought tolerant crop (due to drought escape behavior), it is highly sensitive to drought and heat stresses from early flowering to achene filling due to inefficiency in regulating the leaf expansion and transpiration rates under inadequate availability of soil moisture (García-López et al., 2014). The decline in soil moisture leads to leaf wilting, which results in substantial yield reduction in semi-arid areas receiving the low rainfall (Aboudrare et al., 2006). Several reports indicate that drought stress significantly reduces sunflower achene yield, oil yield and oil quality globally (Soleimanzadeh et al., 2010; Babaeian et al., 2011; Oraki and Aghaalikhana, 2012; Ibrahim et al., 2016).

Abstract

Ants can act as plant biotic defenses, however, in agricultural ecosystems they are often associated with outbreaks of honeydew-producing pests mainly due to the protection they offer to the plant feeders in exchange for honeydew. In this interaction ants may alter the abundance, diversity and community structure of predators and parasitoids. In the present study, we conducted ant-exclusion experiments in three commercial citrus orchards, each one dominated by one ant species (Pheidole pallidula, Lasius grandis or Linepithema humile) during two consecutive years. We then compared the abundance, species richness, diversity and community structure of predators and parasitoids between the ant-allowed and ant-excluded treatments. A total of 176,074 natural enemies belonging to 81 taxa were captured and identified. The abundance of the natural enemies showed a species specific response between treatments. When examining functional groups of natural enemies the abundance of generalist predators decreased while that of parasitoids increased in the ant-allowed treatment. The species richness was significantly lower for predators and higher for parasitoids in the ant-allowed treatment. The Shannon diversity index was not different between treatments for predators, whereas parasitoid diversity was significantly higher in the ant-allowed treatment. Finally, the community structure of predators and parasitoids was not significantly different between treatments. These results suggest that ants in citrus are not associated with a dramatic decrease in natural enemy abundance or biodiversity; on the contrary ants were associated with increased parasitoid species richness and diversity. On the other hand, ants negatively affected the abundance of specific natural enemy species, mainly generalist predators. The impact on these predators might explain the higher pest densities associated with ants in citrus.