Carrots are a multi-nutritional food source. They are an important root vegetable, rich in natural bioactive compounds, which are recognised for their nutraceutical effects and health benefits. This review summarises the occurrence, biosynthesis, factors affecting concentration, and health benefits of phytochemicals found in Daucus carota. Two hundred and fifty-five articles including original research papers, books, and book chapters were analysed, of which one hundred and thirty articles (most relevant to the topic) were selected for writing the review article. The four types of phytochemicals found in carrots, namely phenolics, carotenoids, polyacetylenes, and ascorbic acid, were summarised. These chemicals aid in the risk reduction of cancer and cardiovascular diseases due to their antioxidant, anti-inflammatory, plasma lipid modification, and anti-tumour properties. Numerous factors influence the amount and type of phytochemicals present in carrots. Genotype (colour differences) plays an important role; high contents of α and β-carotene are present in orange carrots, lutein in yellow carrots, lycopene in red carrots, anthocyanins in the root of purple carrots, and phenolic compounds abound in black carrots. Carotenoids range between 3.2 mg/kg and 170 mg/kg, while vitamin C varies from 21 mg/kg to 775 mg/kg between cultivars. Growth temperatures of carrots influence the level of the sugars, carotenoids, and volatile compounds, so that growing in cool conditions results in a higher yield and quality of carrots, while higher temperatures would increase terpene synthesis, resulting in carrots with a bitter taste. It is worthwhile to investigate the cultivation of different genotypes under various environmental conditions to increase levels of phytochemicals and enhance the nutritional value of carrot, along with the valorisation of carrot by-products.

Iron (Fe) and zinc (Zn) nutrient enrichment of staple crops through biofortification can contribute to alleviating micronutrient deficiency in sub-Saharan Africa. A line × tester mating design was used to determine the general combining ability (GCA), specific combining ability (SCA) and heterosis for grain yield, iron, Zn and phytic concentration of six lines crossed with three testers. Lines and testers were selected for high, intermediate and low mineral content. The F1 hybrids and parental lines were evaluated under low nitrogen (N) and optimum conditions across four environments over two seasons. Under low N conditions, Fe and Zn concentration in grain, and grain yield of genotypes were reduced by 9%, 9%, and 59%, respectively. However, phytic acid concentration in grain was increased by 10% under low N conditions. Both additive and non-additive gene effects were important in controlling Fe, Zn and phytic acid concentration in grain and grain yield of maize under both N conditions. The preponderance of GCA effects indicates the importance of additive gene effects in the inheritance of grain yield. Line GCA effects were more sensitive to N conditions across the environments than the tester GCA. High and significant positive SCA effects for grain yield, Fe and Zn content under low N conditions, would be a good indicator of possible heterosis in these traits. Hybrid CBY101 LM-1600 × CBY358 LM-1857 had high and significant positive SCA for grain yield under low N conditions and is a promising candidate for production in low N environments. CBY358 LM-1857 (tester) and CBY102 LM-1601 (line) are a good general combiners for Fe, Zn and GY can be used as parents in future maize hybrid breeding programs to develop high-yielding maize genotypes with high Fe and Zn content.

Maize is the staple food crop for millions of people in sub-Saharan Africa. Iron (Fe) and zinc (Zn) deficiency is a significant health risk that mainly affects low-income populations who rely solely on maize-based diets. This problem can be alleviated by developing micronutrient-rich maize grain. The aim of this study was to determine the adaptation and performance of hybrids for Fe and Zn concentration and grain yield under low soil nitrogen (N) and optimal conditions. Eighteen hybrids derived from lines and testers with low, medium, and high Fe and Zn concentration were grown during the summer rainy seasons of 2017 and 2018 at three locations under low and optimal N conditions. There were significant genotype and environment effects for grain yield, and Fe and Zn concentration, but the genotype by environment interaction effects were the largest, accounting for between 36% and 56% of variation under low N conditions. Low N levels significantly reduced grain yield, and Fe and Zn concentration. Hybrids G1, G2, G4, G7, G10, G11, and G16 were relatively stable, with relatively high mean Fe and Zn concentrations, and low additive main effects and multiplicative interaction (AMMI) stability values and iron stability index (FSI) and zinc stability index (ZSI) under low N conditions. These genotypes can be considered for production under low N stress conditions. Two environments (E4 and E3) were identified for good discriminatory power for genotype performance in terms of Fe and Zn content, respectively. Stable and high-yielding genotypes with high Fe and Zn concentration can be used as biofortified hybrids, which can contribute to a sustainable solution to malnutrition in the region, especially under low N conditions.

Xenia is the immediate effect of pollen on seed development after pollination. This study was conducted to investigate xenia’s effects on Fe and Zn concentration in self- and open-pollinated maize seeds. Eighteen maize hybrids derived from parents with varying concentrations of Fe and Zn were planted at Potchefstroom, Cedara and Vaalharts in South Africa for two seasons, 2017 and 2018. Open- and self-pollinated seeds were compared. Self-pollination of five selected healthy maize hybrids of uniform height from each plot was performed. Fe, Zn and phytic acid (Pa) analysis was conducted on self -and open-pollinated maize seeds, and the molar ratios of Fe and Zn to Pa were also calculated to assess the bioavailability of Fe and Zn. The ranges of Fe, Zn and Pa, and the molar ratios of Fe and Zn to Pa in self-pollinated maize seeds were 15.93–21.36 mg kg⁻¹, 18.50–24.34 mg kg⁻¹, 4.63–5.84 mg g⁻¹, 21.97–31.22 and 23.53–30.16 under high N, and 12.76–19.29 mg kg⁻¹, 16.78–23.50 mg kg⁻¹, 5.05–6.48 mg g⁻¹, 26.12–44.54 and 25.44–35.94 under low N conditions, respectively. The ranges of Fe, Zn and Pa, and the molar ratios of Fe and Zn to Pa in open-pollinated seeds were 14.34–19.12 mg kg⁻¹, 17.27–23.27 mg kg⁻¹, 4.96–5.89 mg g⁻¹, 20.90–28.22 and 22.92–29.37 under high N, and 12.54–18.39 mg kg⁻¹, 16.94–20.93 mg kg⁻¹, 5.30–6.17 mg g⁻¹, 27.90–38.75 and 27.95–36.34 under low N conditions, respectively. The bioavailability of Fe and Zn was high in self-pollinated seeds under high N conditions, while Fe was higher in self-pollinated seeds, and Zn was higher in open-pollinated seeds under low N conditions. Combined over seasons, there were no significant differences between the values of Fe and Zn in self- and open-pollinated seeds under both high N and low N conditions. This indicated that unknown males had no influence on Fe and Zn concentration in maize. Therefore, either self- or open-pollinated seeds can be used for Fe and Zn determination in maize crosses.

Barley (Hordeum vulgare L.) is a monocot plant belongs to the family Poaceae or Graminae that is cultivated among temperate regions of the world. This family includes food and feed grain crops (rice, wheat and maize) that serve as staple foods across the globe. According to FAO, it is the fourth most cultivated crop among grains after maize, rice and wheat. Barley is used in processed and fermented forms for human consumption and used fresh and raw for animal feeds. This chapter contains three major sections. The first section includes fungi, bacteria, viruses, and nematodes. These pathogens confer serious biotic threats to the sustainable production of barley. The economically most important diseases of barley included in this chapter are (1) fungal pathogens, including black points, head blight, leaf and spot blotches, wilts, rusts, smuts, root rots, take-all disease, and powdery mildew; (2) bacterial pathogens afflicting bacterial blights and bacterial streaks; (3) viral pathogens causing barley mosaic and barley yellow dwarf diseases; and (4) root-knot nematodes. The second section of the chapter discusses abiotic stress caused by climate change such as drought, salinity, and heat stress and recent developments in their management. The third section includes herbal parasites of barley, including noxious weeds. The weed section highlights an important outlook on weed management in barley.