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Foliar fertilisation is an alternative form of nutrient application, which is of particular interest for phosphorus (P), where the efficiency of soil fertilisation is low. However, the uptake of foliar-applied nutrients is insufficiently characterised. The aim of this study was to investigate the individual and combined significance of wettability, foliar fertiliser properties and surfactant on foliar P uptake in P-deficient maize (Zea mays L.). Sorption and desorption properties of two P salts used as foliar fertilisers (KH2PO4, K2HPO4) were determined with dynamic vapor sorption isotherms. Leaf surfaces and foliar spray depositions of two differently wettable maize cultivars were investigated by scanning electron microscopy and contact angle measurement. Phosphorus uptake was then linked to leaf and fertiliser solution properties and its effect on cell ultrastructure was characterised by transmission electron microscopy. Wettability was the key factor for P absorption, as all foliar fertilisers were taken up reaching a tissue-P level of adequately nourished plants. For unwettable leaves, only solutions with surfactant, especially the combination of surfactant and hygroscopic P salt (K2HPO4) were taken up. This study provides novel insights into the significance of leaf surface and fertiliser properties, which can thus contribute to an improvement of P fertilisation strategies.

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Maize plays a significant role among rural farming households in South Africa. The study therefore estimated the drivers of maize cultivars' selection choices among rural farming households focusing on the commonly grown cultivars from the study area (Landrace and genetically modifies [GM] maize). A cross-sectional survey of 650 respondents randomly selected from Port St Johns and King Sabata Dalindyebo Local Municipalities of the Eastern Cape Province of South Africa were used. Descriptive results revealed that a significant number of the respondents from the study area (65%) were growing Landrace maize cultivars, followed by GM maize (31%), improved OPVs (3%) and conventional hybrids (1%). Multivariate Probit regression estimates show that GM maize cultivars' selection is positively influenced by the amount of rainfall (1% level), household size (5% level), education (1% level), size of arable land (10% level) and access to cell phones (5% level), whilst negatively influenced by the employment status (5%). Conversely, the selection of Landrace maize cultivars is negatively influenced by the of amount rainfall (1% level), education (1% level), income (10% level), access to cell phone (10% level) and radio (10% level) whilst positively influenced by the number of livestock (5% level). The study therefore argues that GM maize cultivars may be meaningfully promoted in high rainfall areas, focusing on arable land sizes and targeted awareness campaigns. The promotion of Landrace maize cultivars may be targeted in low rainfall areas in a mixed farming setting to enhance the complementarity of maize and livestock.

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Maize-dependent populations in sub-Saharan Africa are continually exposed to aflatoxin poisoning owing to their regular consumption of this dietetic cereal. Being a staple in Kenyan households, consumption of maize-based meals is done almost daily, thereby exposing consumers to aflatoxicoses. This study assessed awareness levels, knowledge disparities, and perceptions regarding aflatoxin contamination at the post-harvest phase among farmers in the Rift Valley Region of Kenya. Households were randomly selected using a geographical positioning system (GPS) overlay of the agro-ecological zones within Uasin Gishu and Elgeyo Marakwet counties. Face-to-face interviews were conducted in 212 smallholder and large-scale farms. The study documented the demographic profiles of farmers and knowledge, awareness, and perceptions of aflatoxin contamination using a pre-designed structured questionnaire. Most farmers were familiar with aflatoxins and the adverse effects they present to health (61.32%). Almost all the farmers (94.37%) were aware of storage molds and food-spoilage fungi. However, few farmers adopted good post-harvest practices (PHPs), such as avoiding premature harvests (49.8%), using well-ventilated storage spaces (44.6%), grain sorting (30.5%), proper drying of maize (17.8%), and using hermetic bags for storage (30.5%). Conclusively, intensified farmer education is required to train farmers on good PHPs to protect their maize from aflatoxigenic fungi and aflatoxin accumulation.

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Cadmium (Cd) being a non-essential, mobile, and toxic heavy metal, negatively affects the plant growth and physiology. Current work investigated the impact of Serratia marcescens CP-13 inoculation on root organic acids and nutrient exudates of two maize cultivars varying in Cd tolerance under induced Cd toxicity. Seedlings of Cd-sensitive (Sahiwal-2002) and Cd-tolerant (MMRI-Yellow) cultivars were grown either inoculated or non-inoculated with CP-13 in Petri plates having various Cd stress levels (0, 6, 12, 18, 24, 30 µM). Seedlings were transferred to rhizoboxes for the collection of root exudates and analysis of physio-biochemical traits. Both maize cultivars exuded higher organic acids and nutrient exudates under non-inoculated conditions as compared to inoculated ones. Non-inoculated tolerant cultivar exhibited higher nutrient accumulation, biomass, antioxidants, total chlorophyll, Cd release meanwhile reduced Cd uptake, lipid peroxidation, exudation of organic acids, and nutrients than the sensitive one. However, under CP-13 inoculation, Cd sensitive cultivar exhibited less exudation of organic acids (citric acid, acetic acid, malic acid, glutamic acid, formic acid, succinic acid, and oxalic acid), nutrients mobilization (K, Na, Zn, Ca, and Mg), total chlorophyll, antioxidants (APX, SOD, POD), total soluble sugar, diminished MDA, and Cd uptake. The significant reduction in release of root exudates by both cultivars was likely due to the plant growth promoting traits of CP-13 which confer Cd tolerance. The maximum release of rhizospheric root exudates were documented at 30 µM applied Cd stress. Therefore, the Serratia sp. CP-13 was proposed as a potential inoculant for bioremediation of Cd together with maize cultivars.

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There is little knowledge of the microbial diversity, mycotoxins and associated secondary metabolites in GM maize and isogenic non-GM cultivars (cvs). This study has quantified the microbial populations and dominant fungal genera in 6 cvs of each type representative of herbicide, pesticide or stacked resistance to both. The predominant mycotoxins and targeted metabolomics profiles were also compared between the two sets of cvs. This showed that the overall fungal populations were 8.8 CFUs g-1 maize. The dominant genera, isolated from maize samples, whether surface-sterilised or not, in all maize cvs were Fusarium, followed by Penicillium, Aspergillus and occasionally Cladosporium and Alternaria. The analysis of the targeted metabolomics showed that approx. 29 different metabolites were detected. These were dominated by fumonisins and minor Penicillium spp. metabolites (questiomycin A and rugulovasine A). Interestingly, the range and number of mycotoxins present in the GM cvs were significantly lower than in the non-GM maize samples. This suggests that while the fungal diversity of the two types of maize appeared to be very similar, the major contaminant mycotoxins and range of toxic secondary metabolites were much lower in the GM cvs.

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Cadmium is a phytotoxic metal which threatens the global food safety owing to its higher retention rates and non-biodegradable nature. Optimal study of microbe-assisted bioremediation is a potential way to minimize the adversities of Cd on plants. Current study was aimed to isolate, identify and characterize Cd tolerant PGPBs from industrially contaminated soil and to evaluate the potential of plant-microbe synergy for the growth augmentation and Cd remediation. The Acinetobacter sp. SG-5, identified through 16S rRNA gene sequence analysis, was able to tolerate 1000 mg/l of applied Cd stress and ability of in vitro indole-3-acetic acid production, phosphate solubilization, as well as 1-aminocyclopropane-1-carboxylic acid deaminase activity. A Petri plate experiment was designed to investigate the impact of Acinetobacter sp. SG-5 on applied Cd toxicity (0, 6, 12, 18, 24, 30 µM) in maize cultivars (3062-Cd tolerant, 31P41-Cd susceptible). Results revealed that non-inoculated maize plants were drastically affected with applied Cd treatments for growth, antioxidants and mineral ions acquisition predominantly in susceptible cultivar (31P41). PGPB inoculation positively influenced the maize growth by enhanced anti-oxidative potential coupled with optimum level of nutrients (K, Ca, Mg, Zn). Analysis of morpho-physio-biochemical traits after PGPB application revealed that substantial Cd tolerance was acquired by susceptible cv. 31P41 than tolerant cv. 3062 under applied Cd regimes. Research outcomes may be important for understanding the growth responses of Cd susceptible and tolerant maize cultivars under Acinetobacter sp. SG-5 inoculation and likely to provide efficient approaches to reduce Cd retention in edible plant parts and/or Cd bioremediation.

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Phytate is the most abundant form of soil organic phosphorus (P). Increased P nutrition of arbuscular mycorrhizal plants derived from phytate has been repeatedly reported. Earlier studies assessed acid phosphatase rather than phytase as an indication of mycorrhizal fungi-mediated phytate use. We investigated the effect of mycorrhizal hyphae-mediated phytase activity on P uptake by maize. Two maize (Zea mays L.) cultivars, non-inoculated or inoculated with the arbuscular mycorrhizal fungi Funneliformis mosseae or Claroideoglomus etunicatum, were grown for 45 days in two-compartment rhizoboxes, containing a root compartment and a hyphal compartment. The soil in the hyphal compartment was supplemented with 20, 100, and 200 mg P kg-1 soil as calcium phytate. We measured activity of phytase and acid phosphatase in the hyphal compartment, hyphal length density, P uptake, and plant biomass. Our results showed: (1) phytate addition increased phytase and acid phosphatase activity, and resulted in larger P uptake and plant biomass; (2) increases in P uptake and biomass were correlated with phytase activity but not with acid phosphatase activity; (3) lower phytate addition rate increased, but higher addition rate decreased hyphal length density. We conclude that P from phytate can be taken up by arbuscular mycorrhizal plants and that phytase plays a more important role in mineralizing phytate than acid phosphatase.

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An investigation was carried out to examine the combined and individual effects of cadmium (Cd) and arsenic (As) stress on osmolyte accumulation, antioxidant activities, and reactive oxygen species (ROS) production at different growth stages (45, 60, 75, 90 days after sowing (DAS)) of two maize cultivars viz., Dong Dan 80 and Run Nong 35. The Cd (100 µM) and As (200 µM) were applied separately as well as in combination (Cd + As) at 30 DAS. Results revealed pronounced variations in the behavior of antioxidants, osmolytes, and ROS in both maize cultivars under the influence of Cd and As stress. Activities of enzymatic (SOD, POD, CAT and APX, GPX, GR) and non-enzymatic (GSH and AsA) antioxidants, generation of ROS, and accumulation of osmolytes were enhanced with the passage of time; therefore, the maximum values for these attributes were observed at 90 DAS for both cultivars. Exposure of plants to Cd or As stress considerably enhanced the antioxidant activities, ROS, and osmolyte accumulation compared with control, while combined application of Cd + As was more devastating in reducing plant biomass of both maize cultivars. Among cultivars, Dong Dan 80 was better able to negate the heavy metal-induced oxidative damage, which was associated with higher antioxidant activities, greater osmolytes accumulation, and lower ROS production in this cultivar.

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Maize (Zea mays L.) is a multipurpose crop, which is immensely used worldwide for its nutritional as well as medicinal properties. This study evaluates the effect of varying concentrations of nitrogen (N) on accumulation of phenolic acids and antioxidant activity in different maize cultivars, including inbreds, hybrids and a composite, which were grown in natural light under controlled temperature (30°C/20°C D/N) and humidity (80%), with sufficient (4.5mM) and low (0.05mM) nitrogen supply. Seeds of different cultivars were powdered and extracted in a methanol:water (80:20) mixture through reflux at 60-75°C, and the extracts obtained were subjected to high performance thin layer chromatography (HPTLC), using ethyl acetate: acetic acid: formic acid: water (109:16:12:31) solvent system for the separation of phenolic acids. Antioxidant activity of the extracts was determined by 2,2-diphenyl-1-picrylhydrazyl (DPPH) and H2O2-scavenging activity assays. At sufficient nitrogen condition, the contents of different phenolic acids were higher in the composite cultivar (8.7 mg g-1 d.wt. in gallic acid to 39.3 mg g-1 d.wt. in cinnamic and salicylic acids) than in inbreds and hybrids. Under low nitrogen condition, the phenolic acids contents declined significantly in inbreds and hybrids, but remained almost unaffected in the composite. The antioxidant activity was also the maximum in the composite, and declined similarly as phenolic acids under low nitrogen supply, showing a significant reduction in inbreds and hybrids only. Therefore, the maize composite has a potential for being used as a nutraceutical in human-health sector.

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