Suboptimal Growing Conditions Research Articles

Mitigating Salt Stress with Biochar: Effects on Yield and Quality of Dwarf Tomato Irrigated with Brackish Water.

The increase in the frequency and magnitude of environmental stresses poses a significant risk to the stability of food supplies. In coastal areas of the Mediterranean, brackish water has long been considered a limitation on horticultural production. In this scenario, the use of biochar in agriculture could be considered a valuable tool to cope with the deleterious effects of salt stress. This work aimed to investigate, in a protected environment, the effects of different concentrations of biochar (0, 1, and 2% v/v) obtained from poplar (Populus L.) biomass on the yield and quality of dwarf San Marzano ecotype tomatoes irrigated with saline water at different concentrations of NaCl (0, 40 and 80 mM). The increase in salt concentration from 0 to 80 mM NaCl reduced the total yield (-63%) and the number of fruits (-25%), but improved the main quality parameters such as dry matter (+75%), total soluble solids (+56%), and polyphenol content (+43%). Compared to control conditions, biochar supplementation improved the total yield (+23%) and number of fruits (+26%) without altering the functional and organoleptic characteristics of the fruits. The promising results underscore the potential of biochar as a sustainable solution to amend soils in order to improve tomato production under unfavorable conditions such as high salinity. However, there is a need to clarify which adaptation mechanisms triggered by biochar amending improve production responses even and especially under suboptimal growing conditions.

Growth, Photosynthesis and Yield Responses of Common Wheat to Foliar Application of Methylobacterium symbioticum under Decreasing Chemical Nitrogen Fertilization

Current agriculture intensifies crop cultivation to meet food demand, leading to unsustainable use of chemical fertilizers. This study investigates a few physiological and agronomic responses of common wheat following the inoculation with plant growth-promoting bacteria to reduce nitrogen inputs. A field trial was conducted in 2022–2023, in Legnago (Verona, Italy) on Triticum aestivum var. LG-Auriga comparing full (180 kg ha−1) and reduced (130 kg ha−1) N doses, both with and without foliar application at end tillering of the N-fixing bacterium Methylobacterium symbioticum. Biofertilization did not improve shoot growth, while it seldom increased the root length density in the arable layer. It delayed leaf senescence, prolonged photosynthetic activity, and amplified stomatal conductance and PSII efficiency under the reduced N dose. Appreciable ACC-deaminase activity of such bacterium disclosed augmented nitrogen retrieval and reduced ethylene production, explaining the ameliorated stay-green. Yield and test weight were unaffected by biofertilization, while both glutenin-to-gliadin and HMW-to-LMW ratios increased together with dough tenacity. It is concluded that Methylobacterium symbioticum can amplify nitrogen metabolism at a reduced nitrogen dose, offering a viable approach to reduce chemical fertilization under suboptimal growing conditions for achieving a more sustainable agriculture. Further research over multiple growing seasons and soil types is necessary to corroborate these preliminary observations.

Synthesis and characterization of Lanthanum Oxide nanoparticles using Citrus aurantium and their effects on Citrus limon Germination and Callogenesis

The plant extract-mediated method is eco-friendly, simple, safe, and low-cost, using biomolecules as a reducing agent to separate nanoparticles. Lanthanum (La) is a rare earth metal that positively affects plant growth and agriculture. Citrus limon is a leading citrus fruit with many varieties. Conventional vegetative propagation methods depend on season, availability of plant material and are time-consuming. It is the main reason for limiting the acceptance of new varieties. So, In-vitro propagation of the lemon method is practiced overcoming all these problems. Lanthanum oxide nanoparticles (La2O3-NPs) were synthesized using plant extract of C. aurantium. Ultraviolet (UV)-Visible Spectroscopy, Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Fourier Transform Infrared (FTIR) spectroscopy, and Thermal Gravimetric Analysis (TGA) were used to characterize the synthesized La2O3-NPs. Fabricated La2O3-NPs were oval and spherical, with an average size of 51.1 nm. UV-visible absorption spectra of La2O3-NPs were shown at a sharp single peak at 342 nm and FTIR showed stretching frequency at 455 cm−1-516 cm−1. In the TGA outcome, mass loss was 9.1%. In vitro experiments demonstrated that La2O3-NPs significantly enhanced the germination and growth of C. limon seeds, achieving an 83% germination rate at 5 mg/L concentration, with uncoated seeds showing root initiation at 10 days and shoot formation at 15 days. Furthermore, La2O3-NPs effectively stimulated callus induction and maturation, with optimal responses observed in media containing MS and 2 mg/L 2,4-D, resulting in a maximum callus frequency of 100% from leaves and 87.5% from shoots at 5 mg/L concentration. These findings underscore the potential of La2O3-NPs to improve seed germination rates, seedling vigor, and callogenesis efficiency, suggesting their promising integration into agricultural practices for sustainable crop production, especially in suboptimal growing conditions. Future research is recommended to explore the mechanisms and broader applications of La2O3-NPs across various plant species and environments.

Rootstocks for the Mediterranean citrus industry: current choices and new releases

Modern citriculture relies on the use of rootstocks to guarantee adaptability to environmental and biotic constraints and to speed up the establishment of a potentially unlimited number of homogeneous plants of a specific clone, which in turn ensures uniformity in the production of high-quality fruit. In this contribution, the status of rootstock availability for the Mediterranean citrus industry is described along with its evolution during the last decades. The major turning points in rootstock choice were caused by the spread of new diseases, such as Citrus Tristeza Virus (CTV), that hastened the use of resistant or tolerant rootstocks. In Italy, the growers decisions on rootstock replacement were facilitated by information from rootstock trials performed for more than 70 years in several areas of southern Italy, as well as information from other countries. However, there is still the need to find alternatives to sour orange (which was the most commonly used rootstock before the CTV outbreak), especially for cultivation under suboptimal growing conditions. Nowadays, the process of replacing standard rootstocks with new ones with better performance should be assisted by a long-term evaluation strategy, since negative characteristics can become evident after many years of evaluation in combination with specific scion varieties. Ongoing rootstock breeding programs in different parts of the world and in Italy are critically described.

Effect of organic biostimulants on cannabis productivity and soil microbial activity under outdoor conditions

In 2019 and 2020, we investigated the individual and combined effects of two biofertilizers (manure tea and bioinoculant) and one humic acid (HA) product on cannabis biochemical and physiological parameters and soil CO2 evolution under outdoor conditions. Our hypothesis was that HA would increase the microbial activity in the biofertilizers and synergy of both compounds would promote better plant performance and stimulate soil microbial activity. In 2020, the individual and combined application of biofertilizers and HA increased cannabis height, chlorophyll content, photosynthetic efficiency, aboveground biomass, and bucked biomass by 105, 52, 43, 122, and 117%, respectively. Impacts were greater under suboptimal growing conditions caused by planting delay experienced in 2020. In 2019, planting date occurred in-between the most favorable period and chlorophyll content and photosynthetic efficiency were the only parameters influenced by the application of biostimulants. The discrepancies between the two growing seasons reinforce the evidence of other studies that biostimulants efficacy is maximized under stress conditions. This study could not conclusively confirm that the combined use of biofertilizer + HA is a superior practice since affected plant parameters did not differ from application of the compounds singly. Similarly, only one biofertilizer + HA treatment increased soil microbial activity. More research is needed to define optimum rates and combinations of biofertilizer and stimulants for cannabis.

ERFVII transcription factors and their role in the adaptation to hypoxia in Arabidopsis and crops.

In this review, we focus on ethylene transcription factors (ERFs), which are a crucial family of transcription factors that regulate plant development and stress responses. ERFVII transcription factors have been identified and studied in several crop species, including rice, wheat, maize, barley, and soybean. These transcription factors are known to be involved in regulating the plant's response to low oxygen stress-hypoxia and could thus improve crop yields under suboptimal growing conditions. In rice (Oryza sativa) several ERFVII genes have been identified and characterized, including SUBMERGENCE 1A (SUB1A), which enables rice to tolerate submergence. The SUB1A gene was used in the development of SUB1 rice varieties, which are now widely grown in flood-prone areas and have been shown to improve yields and farmer livelihoods. The oxygen sensor in plants was discovered using the model plant Arabidopsis. The mechanism is based on the destabilization of ERFVII protein via the N-degron pathway under aerobic conditions. During hypoxia, the stabilized ERFVIIs translocate to the nucleus where they activate the transcription of hypoxia-responsive genes (HRGs). In summary, the identification and characterization of ERFVII transcription factors and their mechanism of action could lead to the development of new crop varieties with improved tolerance to low oxygen stress, which could have important implications for global food security.

Configuration of Strawberry Yield, Nutritional and Functional Traits in Response to LPE Application in a Two-Year Study

Lysophosphatidylethanolamine (LPE) is a promising natural lysophospholipid which can be employed as a growth regulator for horticultural purposes. The present research was accomplished to investigate the effects of LPE (0 or 10 ppm) on the yield and quality of “Savana” strawberry plants grown during two consecutive cultivation cycles (I (2020–2021); II (2021–2022)). Plants cultivated in year I and treated with LPE revealed the highest total yield (838.3 g plant−1), marketable yield (735.4 g plant−1) and average marketable fruit weight (39.8 g plant−1). Fruits from year II plants treated with LPE had the highest total phenolics concentration (491.4 mg 100 g−1 dw). LPE significantly enhanced strawberry antioxidant activity, firmness, soluble solids content, ascorbic acid and anthocyanins by 5.2%, 7.6%, 15.3%, 13.8% and 19.7%, respectively, compared with the control. Although LPE application significantly reduced fruit dry matter, yellowness and lightness by 7.2%, 30.1% and 14.6%, respectively, it significantly increased, in year II, anthocyanins, discarded production, fruit lightness and dry matter. Overall, our findings also revealed that, even under sub-optimal growing conditions (year II), LPE application increased important productive and qualitative strawberry parameters.

Orphan Crops: A Best Fit for Dietary Enrichment and Diversification in Highly Deteriorated Marginal Environments.

Orphan crops are indigenous and invariably grown by small and marginal farmers under subsistence farming systems. These crops, which are common and widely accepted by local farmers, are highly rich in nutritional profile, good for medicinal purposes, and well adapted to suboptimal growing conditions. However, these crops have suffered neglect and abandonment from the scientific community because of very low or no investments in research and genetic improvement. A plausible reason for this is that these crops are not traded internationally at a rate comparable to that of the major food crops such as wheat, rice, and maize. Furthermore, marginal environments have poor soils and are characterized by extreme weather conditions such as heat, erratic rainfall, water deficit, and soil and water salinity, among others. With more frequent extreme climatic events and continued land degradation, orphan crops are beginning to receive renewed attention as alternative crops for dietary diversification in marginal environments and, by extension, across the globe. Increased awareness of good health is also a major contributor to the revived attention accorded to orphan crops. Thus, the introduction, evaluation, and adaptation of outstanding varieties of orphan crops for dietary diversification will contribute not only to sustained food production but also to improved nutrition in marginal environments. In this review article, the concept of orphan crops vis-à-vis marginality and food and nutritional security is defined for a few orphan crops. We also examined recent advances in research involving orphan crops and the potential of these crops for dietary diversification within the context of harsh marginal environments. Recent advances in genomics coupled with molecular breeding will play a pivotal role in improving the genetic potential of orphan crops and help in developing sustainable food systems. We concluded by presenting a potential roadmap to future research engagement and a policy framework with recommendations aimed at facilitating and enhancing the adoption and sustainable production of orphan crops under agriculturally marginal conditions.

Unpacking the agroclimatic challenges and determinants of sweetpotato seed conservation and multiplication strategies by smallholder farmers in Southern Ethiopia

ABSTRACT Sweetpotato is increasingly important in sub-Saharan Africa due to its yield potential under sub-optimal growing conditions. But lack of planting material (seed) at the onset of the rains is a major constraint. This study examined smallholder strategies for sweetpotato seed conservation and multiplication, their agroclimatic determinants, and farmers’ perceived drought risk at four sites (Dilla, Chuko, Hawassa, Sodo) in Ethiopia using informant interviews, a survey of 278 households, and agroclimatic statistics. Conservation practices were dictated by farming system and agroecological conditions. The long-term mean length of dry period when multipliers must conserve seeds ranged between 103 and 131 days across sites. Seed multipliers faced high uncertainty of rainfall onset that varied from the end of February to mid-May. Estimated probabilities of moderate and severe droughts affecting seed conservation ranged from 36–75%, and 15–58%, respectively. In drier sites, age of multiplier, land-holding size, sweetpotato production experience and access to extension were positively associated with being a vine multiplier. Knowledge of indigenous conservations strategies should inform seed system intervention design.

Optimal fine fescue mixture seeding dates in the northern United States

AbstractResearch is lacking on best establishment practices of fine fescues (Festuca spp.), such as optimal seeding timings, which are well known for other cool‐season turfgrasses. Our objective was to document establishment and determine optimal seeding timings for mixed stand of fine fescue in multiple cool‐season climate zones in the United States. From 2019 to 2020, an experiment was replicated across four locations in the northern United States to investigate nine monthly fine fescue mixture seeding timings from March through November. Fine fescue seedling emergence typically hastened as temperatures increased during the growing season, and emergence required 6.1–9.4 d when soil temperatures were within a range of 15–25 °C. Final grid count data across multiple sites indicated that seeding fine fescues in August, September, and at times, July, will likely produce the best establishment with the lowest weed infestation pressure, and there may be more flexibility in seeding timings in a Mediterranean climate, such as Oregon. Seeding fine fescues in the early‐spring or late‐autumn can be more unreliable because of greater likelihood of weed infestation, suboptimal growing conditions, and potential of a late‐autumn seeding to act as an unintended dormant seeding. Results indicate the weed invasion pressure of specific weeds will vary depending life cycle of weed and seeding time of year. Overall, seeding a fine fescue mixture in August or September will increase likelihood of success in cool‐season climate zones in the United States with a wider seeding window when planting in Mediterranean climates.

Elevated Temperatures Negatively Affect Olive Productive Cycle and Oil Quality

Climate change, with elevated temperatures throughout the year, affects many stages of the reproductive growth and development of olives as well as oil quality at harvest. Although olive (Olea europaea L.) is well adapted to the environmental conditions of the Mediterranean Basin, agricultural techniques and breeding through selection programs will have to adapt to these climate change, threatening to worsen in the near future. Defining the pathways controlling high fruit productivity and oil quantity and quality, despite elevated temperatures and sub-optimal growing conditions, is important for coping with current and predicted climate changes. As breeding programs aiming to address these crucial changes may take several decades, an urgent need to designate specific olive cultivars that are more resistant to high temperatures emerges.

Complete replacement of maize grain with sorghum and pearl millet grains in Jumbo quail diets: Feed intake, physiological parameters, and meat quality traits.

In sub-Saharan Africa, the use of maize (Zea mays L.) grain as an energy source in poultry feeds has become unsustainable due to competing demands and suboptimal growing conditions for the maize crop. Sorghum (Sorghum bicolor Moench L.) and pearl millet (Pennisetum glaucum) grains are potential sustainable alternatives, given their tolerance to local growing conditions. Therefore, this study evaluated the effect of total replacement of maize grain with whole or crushed sorghum and pearl millet grains on feed intake, and physiological and meat quality parameters of Jumbo quail. Five experimental diets were formulated by completely replacing crushed maize grain in a commercial grower diet (CON) with whole sorghum (WSG), crushed sorghum (CSG), whole millet (WMG), or crushed millet (CMG). Three hundred and fifty, two-week-old Jumbo quail chicks (74.7 ± 8.81 g live-weight) were evenly distributed into 35 replicate pens to which the experimental diets were allotted. Statistically similar (P > 0.05) weight gain and FCE values were observed between birds reared on the control and pearl millet-based diets. However, birds fed with sorghum-based diets had the lowest FCE and weight gain. Blood parameters fell within the normal ranges reported for healthy quail. Birds fed the whole sorghum grain diet had the least (P < 0.05) serum calcium and higher monocytes, cholesterol, and alkaline phosphatase (ALP) concentrations compared to those reared on the control diet. Compared to the control, the whole sorghum-containing diet reduced (P < 0.05) carcass, breast, wing, thigh, drumstick, liver, gizzard, and large intestine weights of the birds. Complete replacement of maize grain with pearl millet grain (whole or crushed) did not compromise feed intake, growth performance, and meat quality traits of the Jumbo quail birds. However, whole sorghum grain reduced growth performance of the birds.

Similar Yield Benefits of Hybrid, Conventional, and Organic Tomato and Sweet Pepper Varieties Under Well-Watered and Drought-Stressed Conditions

Global agrobiodiversity is threatened by the replacement of traditional, locally adapted crop varieties with high-yielding and hybrid varieties during the past 60 years, resulting in associated losses of crop, variety, and allele diversity. Locally adapted, traditional varieties are known to perform equal or even better under environmental stress conditions and to be more resilient in unstable cultivation environments. Therefore, European organic vegetable breeding organizations conserve local, traditional varieties and breed new varieties in low-input organic environments, aiming to increase the range of varieties for sustainable cultivation under sub-optimal growing conditions. However, performance of organic vegetable varieties, in comparison to conventional high-yielding and hybrid varieties, under different environmental conditions has not been intensively researched. To contribute to this scientific field, we compared the agronomic and quality performance between hybrid, conventional, and organic tomato and sweet pepper varieties, two economically important species on the EU market under a) well-watered and b) drought stress conditions, using five different varieties (i.e., 30 varieties) as replicates in each of the six groups. Performance of both species was negatively affected by drought, regardless of the breeding background. Equally, for tomato and sweet pepper, hybrids produced higher amounts of individual fruits, however total yield in kg was comparable for hybrid, conventional and organic plants. Considering the agro-ecological importance of enlarging and securing variety diversity in light of changing environmental conditions, we show that the assumed benefits of the hybrids can also be delivered by the organic and conventional varieties. These varieties should be considered as an important source of genetic resources, supporting farmers to adapt to their local climate and environmental conditions in the future.

You Want it Sweeter: How Glycosylation Affects Plant Response to Oxidative Stress.

Oxidative stress is a cellular threat which puts at risk the productivity of most of crops valorized by humankind in terms of food, feed, biomaterial, or bioenergy. It is therefore of crucial importance to understand the mechanisms by which plants mitigate the deleterious effects of oxidizing agents. Glycosylation of antioxidant molecules and phytohormones modifies their chemical properties as well as their cellular and histological repartition. This review emphasizes the mechanisms and the outcomes of this conjugation reaction on plant ability to face growing conditions favoring oxidative stress, in mirror with the activity of deglycosylating enzymes. Pioneer evidence bridging flavonoid, glycosylation, and redox homeostasis paved the way for numerous functional analyses of UDP-glycosyltransferases (UGTs), such as the identification of their substrates and their role to circumvent oxidative stress resulting from various environmental challenges. (De)glycosylation appears as a simple chemical reaction regulating the biosynthesis and/or the activity of a myriad of specialized metabolites partaking in response to pathogen and abiotic stresses. This outcome underlies the possibility to valorize UGTs potential to upgrade plant adaptation and fitness in a rising context of sub-optimal growing conditions subsequent to climate change.

The Metabolic Reprogramming Induced by Sub-Optimal Nutritional and Light Inputs in Soilless Cultivated Green and Red Butterhead Lettuce.

Sub-optimal growing conditions have a major effect on plants; therefore, large efforts are devoted to maximizing the availability of agricultural inputs to crops. To increase the sustainable use of non-renewable inputs, attention is currently given to the study of plants under non-optimal conditions. In this work, we investigated the impact of sub-optimal macrocations availability and light intensity in two lettuce varieties that differ for the accumulation of secondary metabolites (i.e., ‘Red Salanova’ and ‘Green Salanova’). Photosynthesis-related measurements and untargeted metabolomics were used to identify responses and pathways involved in stress resilience. The pigmented (‘Red’) and the non-pigmented (‘Green Salanova’) lettuce exhibited distinctive responses to sub-optimal conditions. The cultivar specific metabolomic signatures comprised a broad modulation of metabolism, including secondary metabolites, phytohormones, and membrane lipids signaling cascade. Several stress-related metabolites were altered by either treatment, including polyamines (and other nitrogen-containing compounds), phenylpropanoids, and lipids. The metabolomics and physiological response to macrocations availability and light intensity also implies that the effects of low-input sustainable farming systems should be evaluated considering a range of cultivar-specific positive and disadvantageous metabolic effects in addition to yield and other socio-economic parameters.

Boosting leaf contents of rutin and solanesol in bio-waste of Solanum lycopersicum

In tomato production, the accruing green biomass shows promising potential as source of health-promoting compounds, such as rutin and solanesol, that are of high interest due to their medicinal properties. Naturally, they accumulate in plants growing in suboptimal growing conditions, e.g. influenced by biotic and abiotic stressors. With the aim to evaluate the potential use of tomato residues as source, we analyzed both leaf metabolites during a complete cultivation cycle, while applying single and combined stresses practically realized in greenhouse production.In the late season, contents of both metabolites were significantly enhanced by nutrient deficit in combination with 2 °C colder nights for 4 weeks and prolonged for in total 9 weeks. Particularly, higher solanesol contents were achieved by salt stress and elevated temperature after one week, even stronger when combined with drought. At harvest, stressed plants consist of less green biomass reducing the overall economic potential. However, practicable abiotic stresses should be considered as potential tool to induce the accumulation of beneficial compounds. Extracting profitable metabolites from the green biomass of the model crop tomato supports the overall goal to promote sustainable approaches in horticultural production.

Stress-resilient maize for climate-vulnerable ecologies in the Asian tropics

Most parts of the Asian tropics are hotspots of climate change effects and associated weather variabilities. One of the major challenges with climate change is the uncertainty and inter-annual variability in weather conditions as crops are frequently exposed to different weather extremes within the same season. Therefore, agricultural research must strive to develop new crop varieties with inbuilt resilience towards variable weather conditions rather than merely tolerance to individual stresses in a specific situation and/or at a specific crop stage. C4 crops are known for their wider adaptation to range of climatic conditions. However, recent climatic trends and associated variabilities seem to be challenging the threshold limit of wider adaptability of even C4 crops like maize. In collaboration with national programs and private sector partners in the region, CIMMYT-Asia maize program initiated research for development (R4D) projects largely focusing on saving achievable yields across range of variable environments by incorporating reasonable levels of tolerance/resistance to major abiotic and biotic stresses without compromising on grain yields under optimal growing conditions. By integrating novel breeding tools like - genomics, double haploid (DH) technology, precision phenotyping and reducing genotype × environment interaction effects, a new generation of maize germplasm with multiple stress tolerance that can grow well across variable weather conditions were developed. The new maize germplasm were targeted for stress-prone environments where maize is invariability exposed to a range of sub-optimal growing conditions, such as drought, heat, waterlogging and various virulent diseases. The overarching goal of the stress-resilient maize program has been to achieve yield potential with a downside risk reduction.

Photosynthetic performance of silver fir (Abies alba) of different origins under suboptimal growing conditions.

Understanding of the intraspecific variability in the physiological stress response of trees may enable to mitigate the impact of climate change on forest ecosystems in the future. We studied the photosynthetic performance of five silver fir (Abies alba Mill.) provenances originating from climatically distinct localities. The study was performed in the trial plot of the silver fir provenance experiment IUFRO 2005 on two dates: in the early summer and in the late summer. Heat waves and a decrease in water availability occurred between the two measurement dates, allowing us to study the response of the provenances to suboptimal growing conditions. The provenances were evaluated at the level of PSII photochemistry and CO2 assimilation by measuring photosynthesis-related pigment content, chlorophyll a fluorescence, and gas exchange parameters. Significant climatic clines were confirmed: the photosynthetic performance before and after the stress period increased with the increasing altitude and precipitation at the site of origin. In contrast, photosynthetic performance declined with the increasing temperature and Ellenberg's quotient of the origin site. We concluded that provenances originating from high altitudes, corresponding well with more humid and colder conditions in Central Europe, showed the greatest photosynthetic performance and were less responsive to moderate heat and drought. This documents inter-population variation in physiological traits, which needs to be considered in setting rules and recommendations for the transfer of forest reproductive materials.

Pruning intensity influences growth, flower and fruit development of Moringa oleifera Lam. under sub-optimal growing conditions in Gauteng, South Africa

Moringa oleifera Lam. is becoming increasingly popular as an industrial crop due to its multitude of useful attributes as a water purifier, nutritional supplement and biofuel feedstock. Horticultural practices such as pruning that encourage improved production of M. oleifera in terms of flowers and fruits have been given little attention especially in sub-Sahara Africa. This study therefore aimed to establish an ideal pruning intensity level on ±5 year old M. oleifera trees. A trial was conducted at the University of Pretoria Experimental Farm of the Hillcrest Campus on trees of an established orchard with four treatments namely severe (1 m), moderate (2 m), light (3 m) pruning above the ground level (pollarding), and no pruning (control). These were applied once in September for two consecutive years. Individual inflorescences from each treatment were tagged during floral initiation and monitored throughout until fruiting stage. Records for Leaf Area Index (LAI), fresh and dry biomass, chlorophyll content, as well as tree stem circumference were taken over a period time at around 81, 98 and 124 days after pruning (DAP). Results showed that light pruning (3 m from the ground) resulted in the highest quantity of flower buds at 124 DAP, and of flowers at 98 DAP in both years. In addition, moderate pruning (2 m from the ground) increased flower number on trees at 124 DAP. Highest quantity of fruits were recorded from the moderate pruning treatment. Measurements done on total leaf area, fresh and dry biomass showed that although plants pruned at 1 m above the ground (severe pruning) received better initial penetration of light into the plant canopy, not enough plant vigor could out-perform plants pruned at 2 m above the ground level. Moderately pruned trees also recorded a substantial increase in stem circumference in comparison to the control and lightly pruned trees at 124 DAP in the first year. Moderate pruning promoted significantly higher total chlorophyll accumulations in mature leaves. Although the onset of low temperatures in both years may have led to increased flower abortion resulting in lower fruit numbers across treatments, results suggest that pruning a M. oleifera tree at 3 m (light) and 2 m (moderate) above ground level under sub-optimal growing conditions in Gauteng, South Africa once a year, will result in maximum flower and fruit harvest. The moderately, but also the severely pruned trees produced more than double the amount of fresh biomass in comparison to the control and lightly pruned trees. This study therefore concludes that M. oleifera crop production for the sole purpose of fruit production may not be optimal in Pretoria, Gauteng, however, leaf production is promising due to the higher plant biomass recorded with the moderate pruning treatment.

The Contribution of Functional Traits to the Breeding Progress of Central-European Winter Wheat Under Differing Crop Management Intensities.

Wheat yields in many of the main producing European countries stagnate since about 20 years. Hence, it is of high interest, to analyze breeding progress in terms of yield and how associated traits changed. Therefore, a set of 42 cultivars (released between 1966 and 2012) was selected and yield as well as functional traits defined by the Monteith and Moss equation were evaluated under three levels of management intensity. The Monteith Moss equation thereby calculates grain yield as the product of incident photosynthetically active radiation, fraction of intercepted radiation, radiation use efficiency, and harvest index. The field trial was performed in a high yielding environment in Northern Germany in two seasons (2016–2017 and 2017–2018) with very contrasting rainfall rates. The three differing managements were: intensive (high N + pesticides), semi-intensive (high N − pesticides), and extensive (low N − pesticides). The results indicate that the stagnation of wheat yields in Central-Europe is not caused by a diminishing effect of breeding on yield potential. This equally applies to suboptimal growing conditions like extensified crop management and restricted water supply. Nearly all functional sub-traits showed a parallel progress but coefficients of determination of relationships between traits and year of variety release are decreasing along the hierarchy of yield formation. One exception is radiation interception which did not show a stable linear increase during breeding history. In recent years, biomass is getting more important in comparison to harvest index. Values of harvest index are slowly approaching theoretical maxima and correlations with grain yield are decreasing.