Lenticels are sites of initiation of microcracking and russeting in 'Apple' mango.

The mango cultivar 'Apple' is an important fruitcrop in Kenya, but it is highly susceptible to russeting. The objective was to establish whether lenticels predispose cv. 'Apple' mango to russeting. Fruit mass and surface area increased in a sigmoidal pattern with time. The frequency of lenticels per unit surface area decreased during development. The number of lenticels per fruit was constant. Lenticels were most frequent in the apex region and least common in the cheek and nak (ventral) regions. The cheek region also had lenticels with the largest core areas, whereas the lenticel core areas in the apex region were significantly smaller. Microscopy revealed stomata became covered over with wax deposits at 33 days after full bloom (DAFB). By 78 DAFB, periderm had formed beneath the pore. At 110 and 161 DAFB, cracks had developed and the periderm had extended tangentially and radially. The presence of lenticels increased the strain released upon excision of an epidermal segment, further strain releases occurred subsequently upon isolation of the cuticle and on extraction of the cuticular waxes. The number of lenticels per unit surface area was negatively correlated with the fruit surface area (r2 = 0.62 **), but not affected by fruit size. Mango cv. 'Apple' had fewer, larger lenticels and more russet, compared with 'Ngowe', 'Kitovu' or 'Tommy Atkins' mango. In cv. 'Apple', the lowest lenticel frequency, the largest lenticels and the most russeting occurred at a growing site at the highest altitude, with the highest rainfall and the lowest temperature. Moisture exposure of the fruit surface resulted in enlarged lenticels and more microcracking of the cuticle. Our results establish that russeting in 'Apple' mango is initiated at lenticels and is exacerbated if lenticels are exposed to moisture.

Exploring the Status of Preference, Utilization Practices, and Challenges to Consumption of Amaranth in Kenya and Tanzania.

African leafy vegetables such as amaranth have been utilized since time immemorial both as food and as medicine. These vegetables grew naturally in most rural environments, but currently most of them are cultivated both for home consumption and for sale. The aim of this study was to identify the most preferred amaranth species and cooking and utilization practices, as well as the beliefs and attitudes that encourage or discourage use of this vegetable. The study was carried out in seven counties of Kenya and in three regions in Tanzania. Twenty Focus Group Discussions (FGDs) with members of the community and twenty Key Informant Interviews (KIIs) with agricultural and nutrition officers were conducted in the study areas to obtain information on preferred varieties, sources of amaranth vegetables, common cooking methods, alternative uses, beliefs and taboos surrounding amaranth consumption, and the challenges experienced in production and consumption. The findings of the study showed that amaranth is one of the most commonly consumed indigenous vegetables in Kenya and Tanzania. The preference for varieties and cooking habits differs depending on the community and individuals. Amaranthus dubius and Amaranthus blitum were most common in Kenya, while Amaranthus dubius and Amaranthus hypochondriacus were most common in Tanzania. Most people consumed these vegetables because they were affordable and available or because of circumstance of lacking other foods. Regarding cooking, final taste was mostly considered rather than nutritional attribute. Several alternative uses of amaranth such as uses as medicine and livestock feed were also reported, as well as some beliefs and taboos surrounding the vegetable. Training on nutritional attributes and promotion of food preparation practices that ensure maximum nutrient benefits from amaranth is needed at the community level to realize the nutritional importance of the vegetables. Hands-on training and demonstrations were the most preferred modes of passing information.

Baobab pulp authenticity and quality control by multi-imaging high-performance thin-layer chromatography.

Globalization of trade and increasing demand for baobab fruit pulp powder (Adansonia digitata) has led to more adulteration incidence with physically similar products, e.g. sifted cereal flours. In this study, 135 baobab samples drawn from trees in Kitui and Kilifi (Kenya) and North and South Kordofan (Sudan) were used as the reference and compared with adulterated (with 10-30% sifted rice, maize and wheat flours) baobab samples using multi-imaging by high-performance thin-layer chromatography. The ethanol - water extracts were separated on a normal phase. Any differences were detected via multi-imaging (UV/Vis/FLD) including diphenylamine alanine o-phosphoric acid, p-anisaldehyde sulfuric acid and p-amino benzoic acid reagents. Raffinose was identified as a marker compound for cereal-based adulteration. The method accuracy (recovery of 95%) and detection from 10-30% flour addition onwards are sufficient to curb economically motivated adulteration, to control product quality and to ensure consumer protection for local and international trade.

Effect of drying methods on the retention of bioactive compounds in African eggplant.

African eggplants (Solanum aethiopicum L.) are a rich source of bioactive compounds and functional constituents that are beneficial to human health. However, the short shelf life of these vegetables can be a major cause of postharvest losses especially during peak harvesting season. Drying is one of the most convenient technologies for the production of shelf stable food products. However, drying can lead to considerable loss of the available bioactive compounds due to thermal degradation depending on the drying method and temperature conditions. This study investigated the effect of four drying methods (solar, oven, vacuum, and freeze) on the retention of total phenolics, beta-carotene, antioxidant capacity, and lycopene in five African eggplant (S. aethiopicum) accessions (sangawili, manyire green, S00047A, AB2, and aubergine blanche). Samples were dried up to ~10% moisture content. The fresh and dried samples were analyzed for total phenolic content, antioxidant capacity, beta-carotene content, and the lycopene content. In the fresh state, beta-carotene, total phenolic content, and free radical scavenging activity ranged between 14.75 ± 0.50 and 29.50 ± 0.77 mg/100 g db, 751.21 ± 1.73 and 1,363.95 ± 2.56 mg/100 g GAE db, and 99.58 and 325.61 mg/ml db IC 50 value, respectively. The accession S00047 showed highest total phenolic content and lowest IC 50 value in the fresh samples. The results also showed that total phenolic content, antioxidant capacity, and beta-carotene contents were significantly (p < .05) affected by drying method and drying temperature with freeze-drying presenting the highest retention. Overall, 36.26%s-95.05% (total phenolics) and 31.44%-99.27% (beta-carotene) were retained during freeze-drying. Lycopene was only detected in the dried samples of the accession manyire green but absent in all the fresh samples of all the accessions. This study demonstrates that freeze-drying was the most effective in retaining the highest bioactive compounds in African eggplants.

Comparative transcriptome analysis reveals distinct ethylene-independent regulation of ripening in response to low temperature in kiwifruit.

BACKGROUND: Kiwifruit are classified as climacteric since exogenous ethylene (or its analogue propylene) induces rapid ripening accompanied by ethylene production under positive feedback regulation. However, most of the ripening-associated changes (Phase 1 ripening) in kiwifruit during storage and on-vine occur largely in the absence of any detectable ethylene. This ripening behavior is often attributed to basal levels of system I ethylene, although it is suggested to be modulated by low temperature. RESULTS: To elucidate the mechanisms regulating Phase 1 ripening in kiwifruit, a comparative transcriptome analysis using fruit continuously exposed to propylene (at 20 °C), and during storage at 5 °C and 20 °C was conducted. Propylene exposure induced kiwifruit softening, reduction of titratable acidity (TA), increase in soluble solids content (SSC) and ethylene production within 5 days. During storage, softening and reduction of TA occurred faster in fruit at 5 °C compared to 20 °C although no endogenous ethylene production was detected. Transcriptome analysis revealed 3761 ripening-related differentially expressed genes (DEGs), of which 2742 were up-regulated by propylene while 1058 were up-regulated by low temperature. Propylene exclusively up-regulated 2112 DEGs including those associated with ethylene biosynthesis and ripening such as AcACS1, AcACO2, AcPL1, AcXET1, Acß-GAL, AcAAT, AcERF6 and AcNAC7. Similarly, low temperature exclusively up-regulated 467 DEGS including AcACO3, AcPL2, AcPMEi, AcADH, Acß-AMY2, AcGA2ox2, AcNAC5 and AcbZIP2 among others. A considerable number of DEGs such as AcPG, AcEXP1, AcXET2, Acß-AMY1, AcGA2ox1, AcNAC6, AcMADS1 and AcbZIP1 were up-regulated by either propylene or low temperature. Frequent 1-MCP treatments failed to inhibit the accelerated ripening and up-regulation of associated DEGs by low temperature indicating that the changes were independent of ethylene. On-vine kiwifruit ripening proceeded in the absence of any detectable endogenous ethylene production, and coincided with increased expression of low temperature-responsive DEGs as well as the decrease in environmental temperature. CONCLUSIONS: These results indicate that kiwifruit possess both ethylene-dependent and low temperature-modulated ripening mechanisms that are distinct and independent of each other. The current work provides a foundation for elaborating the control of these two ripening mechanisms in kiwifruit.

Metabolomic analyses to evaluate the effect of drought stress on selected African Eggplant accessions.

BACKGROUND: Drought stress is one of the main abiotic stresses that affect crops. It leads to biochemical changes that can have adverse effects on plant growth, development and productivity. African eggplants are important vegetable and fruit crops reported to adapt and thrive well under drought stress. The diversified metabolites arising due to stress have not been well defined. A gas chromatographic-mass spectrometric metabolomic approach was applied to characterize the effect of drought stress on metabolites at different stages of growth. Nineteen accessions were selected for analysis and drought was imposed by withholding water until soil moisture reached 60% field capacity. Fresh leaf tissues were sampled before stress, 2 and 4 weeks after stress and metabolite profiling done. RESULTS: Significant changes in metabolite content were observed, and potentially important metabolites with respect to stress responses were characterized. Proline, glutamate, sucrose, fructose and tricarboxylic acid cycle metabolites were shown to be positively correlated with stress. Principal component analysis showed a clear discrimination between the different accessions, growth stages and stress/control conditions. CONCLUSION: The results illustrate that drought stress has a significant impact on the concentrations of some metabolites, such as amino acids, sugars and organic acids, which may contribute to drought stress effects and tolerance. © 2017 Society of Chemical Industry.

Carotenoid profiling of the leaves of selected African eggplant accessions subjected to drought stress.

African eggplants (Solanum aethiopicum and S. macrocarpon) are among the most economically important and valuable vegetable and fruit crops. They are a major source of biologically active nutritional substances and metabolites which are essential for plant growth, development, stress adaptation and defense. Among these metabolites are the carotenoids which act as accessory pigments for photosynthesis and precursor to plant hormones. Though African eggplants are known to be resistant to various abiotic stresses, the effect of these stresses on secondary metabolites has not been well defined. The objective of this study was to establish the effect of drought stress on carotenoid profiles of nineteen African eggplant accessions selected based on leaf and fruit morphological traits. Stress was achieved by limiting irrigation and maintaining the wilting state of the crops. Fresh leaves were sampled at different maturity stages; before stress, 2 weeks and 4 weeks after stress for carotenoid analysis. The fresh harvested leaf tissues were immediately frozen in liquid nitrogen and ground. Analysis was carried out using a Dionex HPLC machine coupled to Photo Array Detector and Chromeleon software package (Thermo Fisher Scientific Inc, Waltham, Massachusetts, USA). Major carotenoids viz;. Xanthophylls (neoxanthin, violaxanthin, zeaxanthin and lutein) and carotenes (ß-carotene and α-carotene), phytofluene, lycopene, phytoene as well as chlorophylls (chlorophyll-b and Chlorophyll-a) were targeted. The carotenoids increased with maturity stage of the crop. Although the stressed crops reported significantly decreased amount of carotenes, chlorophylls, neoxanthin and violaxanthin, the concentration of zeaxanthin increased with stress whereas lutein had no significant change. Chlorophyll-a was significantly high in all the control accessions. Two accessions reported significantly higher contents of carotenoids as compared to the other accessions. The results of this study indicate that water stress has significant impact on the concentration of some carotenoids and photosynthetic pigments. This will definitely add value to the study of stress tolerance in crops.