Investigating the involvement of ABA, ABA catabolites and cytokinins in the susceptibility of 'Nules Clementine' mandarin to rind breakdown disorder.

BACKGROUND: 'Nules Clementine' mandarin was used to investigate the potential involvement of endogenous plant hormones in mediating citrus fruit susceptibility to rind breakdown disorder (RBD). The effect of light exposure (namely canopy position and bagging treatments) on the endogenous concentration of ABA, 7'-hydroxy-abscisic acid (7-OH-ABA), ABA-glucose ester (ABA-GE) and dihydrophaseic acid (DPA), and t-zeatin was tested using four preharvest treatments: outside, outside bagged, inside and inside bagged. Phytohormones concentration was evaluated during nine weeks of postharvest storage at 8 °C. RESULTS: The shaded fruit inside the canopy had the highest RBD score (0.88) at the end of postharvest storage, while sun-exposed fruit had the lowest score (0.12). Before storage, ABA concentration was lowest (462.8 µg kg-1 ) for inside fruit, and highest in outside bagged fruit (680.5 µg kg-1 ). Although ABA concentration suddenly increased from the third week, reaching a maximum concentration of 580 µg kg-1 at week 6 in fruit from inside position, it generally reduced 1.6-fold ranging from 240.52 to 480.65 µg kg-1 throughout storage. The increase of 7-OH-ABA was more prominent in fruit from inside canopy. Overall, the concentration of ABA-GE increased three-fold with storage time. DPA concentration of bagged fruit from inside canopy position was significantly higher compared to outside fruit. The lower ABA-GE and higher DPA concentration in inside bagged fruit throughout storage also coincided with higher RBD. CONCLUSION: The strong positive correlations between 7-OH-ABA, DPA and RBD incidence demonstrated that these ABA catabolites could be used as biomarkers for fruit susceptibility to the disorder. © 2019 Society of Chemical Industry.

Evaluating the efficacy of chitosan and CMC incorporated with moringa leaf extracts on reducing peteca spot incidence on 'Eureka' lemon.

Lemon (Citrus limon L.) is one of the most cultivated citrus fruit in South Africa. In citrus packhouses, fruit are coated with commercial synthetic waxes to enhance shelflife. However, the use of waxes has been linked to peteca spot (PS) incidence in lemons. This study evaluated the efficacy of chitosan (CH) and carboxymethyl cellulose (CMC) incorporated with moringa leaf extracts (M) on reducing peteca spot incidence on 'Eureka' lemon. A total of 500 'Eureka' lemons were harvested from outside and inside canopy positions from a commercial orchard in KwaZulu-Natal, South Africa. Fruit were assigned to five coating treatments, namely; control, 1% M + CMC, 1% CMC, 1% CH and 1% M + CH. After coating, fruit were transferred into a cold room with delivery air temperature set at 3 °C for 12 weeks to induce the disorder. At each sampling week, peteca spot incidence, fruit physicochemical and phytochemical properties including color, mass, vitamin C, carotenoids, TSS, TA and phenolics were measured. The results showed that coating treatments and canopy position significantly affected PS incidence. Fruit coated with M + CMC, CMC, CH were less susceptible to PS development in both inside and outside canopy compared to the control and M + CH coated fruit. Coating treatments significantly affected phenolic and flavonoid concentration. Moreover, coating treatments significantly reduced mass loss, ascorbic acid loss and delayed color change of fruit. The results found in this study demonstrated the ability of either M + CMC, CMC, or CH as coating treatments for reducing PS in 'Eureka' lemon.

Rapid visible-near infrared (Vis-NIR) spectroscopic detection and quantification of unripe banana flour adulteration with wheat flour.

Unripe banana flour is a premium nutritious product with a potential to curb degenerative diseases through resistant starch and gluten free traits, however, with scant techniques to monitor adulteration practices. The objective of the present study was to determine the efficacy of visible-near infrared spectroscopy (Vis-NIR) spectroscopy (Vis-NIRS) in the detection and quantification of unripe banana flour adulteration with wheat flour. To do this, simulated adulteration of a composite banana flour was performed with different levels of wheat flour, in intervals of 20 g kg-1, ranging from 0 to 800 g kg-1. Each level was acquired in duplicate giving a total of 82 samples. Vis-NIR spectral data was acquired using a portable F-750 spectrometer in the range 447-1005 nm. Spectral data was analysed chemometrically using principle components analysis and partial least squares regression (PLSR), with 41 samples used as a calibration set and 41 for validation. The first two principal components accounted for 95% of spectral data variation, revealing five distinct clusters related to 0 g kg-1, 20-200 g kg-1, 220-400 g kg-1, 420-600 g kg-1 and 620-800 g kg-1 adulterated samples. The best PLSR model to predict wheat flour adulteration degrees in unripe banana flour was obtained using 2nd derivative Savitzky-Golay (19-point smoothing, 2nd order polynomial), showing the highest Rc 2 (0.991); Rp 2 (0.993); RPD (12.021) and the lowest RMSEC (2.226 g kg-1) and RMSEP (1.993 g kg-1) values. The obtained Vis-NIRS PLSR models therefore demonstrated the technology novelty in monitoring unripe banana flour quality by the processing industries and in retail markets during product verification.

Effect of ultraviolet irradiation on postharvest quality and composition of tomatoes: a review.

Ultraviolet (UV) irradiation has recently emerged as a possible alternative to currently used postharvest phytosanitary treatments. Research has also highlighted other benefits associated with UV irradiation in postharvest technology. This review presents the effects of UV irradiation on postharvest and nutritional quality of tomatoes. The application of UV irradiation on tomatoes is discussed including its effect on biological (respiration rate, ethylene production and microbial growth), physico-chemical (firmness, colour, total soluble solids and titratable acidity) and nutritional (vitamins, carotenoids, phenolic and antioxidants) quality. UV-treated tomatoes have shown resistance to microbial growth and decay. Although UV irradiation reduces the loss of vitamin C during storage, the loss of vitamin E remains a concern. UV treatments lead to higher antioxidant capacity, flavonoids and phenolic content. UV irradiation significantly reduced carotenoids in certain cultivars. Based on the literature reviewed, the success of UV irradiation treatments is cultivar-dependent. While improved retention of phytochemicals has been reported in UV-C treated fruit, increased losses have been reported in certain cultivars. Research efforts on the development of cultivar-specific UV irradiation protocols are warranted. The effect of harvest maturity and seasonal differences in the efficacy of UV treatments is required to be investigated.

Level of antiretroviral therapy adherence and associated factors during COVID-19 pandemic era in public hospitals of Jigjiga City eastern Ethiopia: a cross-sectional study.

Background: Coronavirus-19 disease is more severe in patients on antiretroviral therapy (ART). Low-income countries, such as those in Sub-Saharan Africa, are particularly vulnerable to the virus' spread. However, there is little information on antiretroviral therapy (ART) use in Ethiopia during the pandemic, particularly in the study area. Therefore, this study aimed to assess the level of antiretroviral treatment adherence and associated factors during the COVID-19 pandemic era in public hospitals in Jigjiga City, Somalia, and Eastern Ethiopia. Methods: An institution-based cross-sectional study was conducted among 382 randomly selected HIV patients on antiretroviral therapy (ART) follow-up in public hospitals in Jigjiga City from March 1-30, 2022. The data was collected through face-to-face interviews and a review of the patient's record. To explore the relationship between variables, both bivariate and multivariable logistic regression analyses were performed. The adjusted odds ratio (AOR) was utilized, along with a 95% confidence interval, to assess the strength and direction of the association. Statistical significance was considered at p < 0.05. Results: The antiretroviral therapy (ART) adherence rate of HIV patients was 76.9% (95% CI, 71.9-82). Disclosing HIV status to sexual partners [AOR = 2.3, (95% CI (1.22-4.19)], having communication with health care providers' [AOR = 3.2, (95% CI (1.57-6.53)], having no history of current substance use [AOR = 2.6, (95% CI (1.45-4.63)], and patients who did not fear COVID-19 infection [AOR = 5.8 (95% CI (11-10.98)] were significantly associated with antiretroviral therapy (ART) adherence. Conclusion: In this study, the level of antiretroviral therapy (ART) adherence was poor in comparison to the expected level. Patients' adherence status was favorably related to disclosing their status to families and having contact with their healthcare providers, whereas worrying about COVID-19 pandemic infection and current substance use was adversely associated.

Morpho-physiological and biochemical characterization of African spider plant (Gynandropsis gynandra (L.) Briq.) genotypes under drought and non-drought conditions.

The African spider plant (Gynandropsis gynandra (L.) Briq.) is a nutrient-dense, climate-resilient indigenous vegetable with a C4 carbon fixation pathway. Understanding African spider plant drought tolerance mechanisms is essential for improving its performance in water-stressed areas. The objective of this study was to evaluate the stress tolerance potential of African spider plant accessions based on thirteen morphological, physiological, and biochemical traits under three different water treatment regimes. Eighteen accessions were evaluated over two growing seasons in the greenhouse using a split-split plot design with four replications and three water treatment-regimes namely optimum (100% field capacity), intermediate drought (50% field capacity) and, severe drought (30% field capacity). The results revealed that water regime had a significant effect (P< 0.01) on the accessions for the traits studied. A significant reduction across most of the studied traits was observed under drought conditions. However, proline content in all the accessions significantly rose under drought conditions. The principal component analysis revealed a considerable difference in the performance of the 18 African spider plant accessions under optimum and drought stress conditions. Several morphological and physiological parameters, including days to 50% flowering (r = 0.80), leaf length (r = 0.72), net photosynthesis (r = 0.76) and number of leaves per plant (r = 0.79), were positively associated with leaf yield under drought conditions. Cluster analysis categorized the 18 accessions and 13 measured parameters into 4 clusters, with cluster-1 exhibiting greater drought tolerance for most of the studied traits, and cluster-4 having the most drought-sensitive accessions. Among the accessions tested, accessions L3 and L5 demonstrated excellent drought tolerance and yield performance under both conditions. As a result, these accessions were selected as candidates for African spider plant drought tolerance breeding programs. These findings will serve as the foundation for future studies and will aid in improving food and nutrition security in the face of drought.

The Antifungal Effect of Gaseous Ozone on Lasiodiplodia theobromae Causing Stem-End Rot in 'Keitt' Mangoes.

This study evaluated the antifungal activity of ozone (O3) against stem-end rot of mango fruit (cv. Keitt). Mango fruit were exposed to gaseous ozone (0.25 mg/L) for 24 or 36 h during cold storage, and control fruit were untreated. Experimental fruit were stored at 90% relative humidity and 10 ± 0.5 °C for three weeks and ripened at ambient temperature for one week. Ozone treatment (24 h) inhibited the mycelial growth of Lasiodiplodia theobromae by 60.35%. At day twenty-eight of storage, fruit treated with O3 for 36 h had low mass loss (%) and high firmness compared to the untreated control fruit. Treating mango fruit with O3 (36 h) maintained the color and concentration of total flavonoids throughout the storage time. At the end of storage, peroxidase activity under the O3 24 h treatment was significantly higher (0.91 U min-1 g-1 DM) compared to O3 (36 h) and control, which, respectively, had 0.80 U min-1 g-1 DM and 0.78 U min-1 g-1 DM. Gaseous ozone for 24 h is recommended as a cost-effective treatment for controlling stem-end rot. These findings suggest that gaseous ozone effectively controlled stem-end rot and enhanced the postharvest quality of mango fruit.

Assessing the Impact of Roasting Temperatures on Biochemical and Sensory Quality of Macadamia Nuts (Macadamia integrifolia).

Depending on the temperature regime used during roasting, the biochemical and sensory characteristics of macadamia nuts can change. 'A4' and 'Beaumont' were used as model cultivars to examine how roasting temperatures affected the chemical and sensory quality of macadamia nuts. Using a hot air oven dryer, macadamia kernels were roasted at 50, 75, 100, 125, and 150 °C for 15 min. The quantity of phenols, flavonoids, and antioxidants in kernels roasted at 50, 75, and 100 °C was significant (p < 0.001); however, these kernels also had high levels of moisture content, oxidation-sensitive unsaturated fatty acids (UFAs), and peroxide value (PV), and poor sensory quality. Low moisture content, flavonoids, phenols, antioxidants, fatty acid (FA) compositions, high PV, and poor sensory quality-i.e., excessive browning, an exceptionally crunchy texture, and a bitter flavor-were all characteristics of kernels roasted at 150 °C. With a perfect crispy texture, a rich brown color, and a strong nutty flavor, kernels roasted at 125 °C had lower PV; higher oxidation-resistant UFA compositions; considerable concentrations of flavonoids, phenols, and antioxidants; and good sensory quality. Therefore, 'A4' and 'Beaumont' kernels could be roasted at 125 °C for use in the industry to improve kernel quality and palatability.

Nanotechnology-enhanced edible coating application on climacteric fruits.

Climacteric fruits continue to ripen after harvest and produce ethylene, coupled with an increase in respiration rate, which contributes to more rapid perishability. Inhibition of ethylene biosynthesis has been shown to be an efficient way to delay the onset of ripening and lengthen shelf life. The use of edible materials as coatings presents an efficient approach in preserving the quality of fruits. Edible coatings have many benefits, such as affordability, ease of application, and use of natural ingredients. Nanotechnology provides interesting approaches to the management of fruit shelf life after harvest. Nanotechnology has the capacity of producing new materials by minimizing the size of components to a nanometric level. These kinds of nanomaterials possess distinct and improved properties for delaying fruit ripening and decay. The main goal of adding nanoparticles to edible coatings is to enhance the biopolymer's mechanical and water vapor barrier properties. Nanoparticles also contain biopolymer-like features and are thought to have superior antibacterial, antifungal, and antiviral properties than edible coatings. This review is aimed at summarizing recent findings on the application of edible coatings in the form of nanoparticles, and their effect on quality parameters and shelf life extension of climacteric fruits. Peer-reviewed articles were obtained by using Scopus and science direct. The current materials widely used for coating climacteric fruits are zinc, silver and chitosan nanoparticles. Zinc nanoparticles have been shown to be more effective in delaying ripening significantly by reducing weight and moisture loss and ensuring retention of fruit firmness. Further research is needed to understand their effect on other physicochemical properties of fruits.

Destructive and rapid non-invasive methods used to detect adulteration of dried powdered horticultural products: A review.

Adulteration monitoring of processed powdered horticultural products is an important aspect of research in order to facilitate fair trade, ensure food authenticity and safety in the agricultural food industries. Globally, a diversity of horticultural powdered products prone to adulteration include herbs and spices; fruit and vegetable flours; hot beverages and medicinal powdered products. This review article focuses on the utilisation of traditional and non-destructive technologies with emphasis on adulteration detection of powdered horticultural products. Nowadays, infrared spectroscopic technologies (visible to near infrared spectroscopy (Vis/NIRS), Fourier transform infrared (FT-IR), hyperspectral imaging and Raman spectroscopy) are preferred for processed product quality verification over conventional approaches (electrophoretic, gas and liquid chromatographic methods, enzyme-linked immunological assay (ELISA), polymerase chain reaction (PCR) and microscopic methods). Various applications of destructive and non-destructive techniques as well as their limitations in the field of powdered products adulteration detection have been extensively reviewed. A discussion on the concepts of adulteration, adulterants as well as the potential impact on health and agri-food industry is provided. The current status of destructive and rapid infrared methods as well as the future research direction for adulteration detection of powdered horticultural products is outlined. Chemometrics application towards developing excellent robust identification models from spectral data analysis to effectively assess the different adulteration levels of spices/herbs, hot beverage powders, fruit/vegetable flours and medicinal powdered products are illustrated.

Effects of stem training on the physiology, growth, and yield responses of indeterminate tomato (Solanum lycopersicum) plants grown in protected cultivation.

The lower yield of tomatoes grown in tunnels, due to the limited space, remains a challenge. Stem training has long been identified as one of the most important horticultural practices used to improve the yield and fruit quality of tomatoes grown in commercial tunnels; however, there is little information available on the dome-shaped tunnels that are used, particularly by smallholder farmers. The common stem-training methods used in tunnels include the Single-Stem (SS), the Double-Stem (DS) and the Two-Plants-per-Pot (TPP) methods. Their effect on the plants' growth, development and physiology varies significantly, and hence, it affects crop productivity. The experiment was conducted in an 8 m × 30 m dome-shaped tunnel and the treatment included the single-stem, double-stem and two-plants-per-pot methods. A higher photosynthetic rate was observed in the SS treatment, followed by the DS treatment. Similar trends were found in the growth, yield and fruit quality parameters of the SS and DS treatments. However, the DS and TPP treatments exhibited, on average, a higher number of fruits, as well as a higher colour index, TSS, TA and Brima per harvest, than the SS treatment. The study indicated that the double-stem and two-plants-per-pot training methods are the best for farmers who seek to optimize their yields and maximize their profits for this cultivar.

Rapid spectroscopic method for quantifying gluten concentration as a potential biomarker to test adulteration of green banana flour.

The demand for gluten-free banana flour has led manufactures to enforce strict measures for quality control. A need has arisen for the development of more sensitive and reliable methods to test the quality of green banana flour (GBF). The objective of this study was to develop rapid visible to near-infrared (Vis-NIR) based spectroscopic models to detect gluten concentration, as a biomarker to detect wheat flour adulteration in green banana flour (GBF). Spectroscopic data were acquired using a desktop (FOSS®) Vis-NIR spectroscopy ranging from 400 to 2500 nm of the electromagnetic spectrum. The spectral and reference data were submitted to principal component analysis (PCA) and partial least squares regression (PLSR) for the development of gluten adulteration detection models. Calibration models were constructed based on a full cross-validation approach, consisting of 51 samples for the calibration set and 21 samples for the test set. PCA scores plot discriminated gluten adulterated and unadulterated GBF samples with 100% accuracy for the first two principal components (PCs). The optimal prediction model was obtained after a combination of baseline (offset and baseline linear correlation) and standard normal variate (SNV) pre-processing technique. This model showed a 94% coefficient of determination of cross-validation (R2cv) and prediction (R2p); root mean square error of cross-validation (RMSECV) of 3.7 mg/kg, root mean square error of prediction (RMSEP) of 3.9 mg/kg; and RPD value of 4. This work has demonstrated that Vis-NIRS method is a robust and feasible technology that may be used to ensure the safety of banana flour and that this product stays gluten-free by providing good and reliable gluten detection and quantification prediction models.

Biopriming with Seaweed Extract and Microbial-Based Commercial Biostimulants Influences Seed Germination of Five Abelmoschus esculentus Genotypes.

Seed germination is a crucial step in plant propagation, as it controls seedling production, stand establishment and ultimately crop yield. Approaches that can promote seed germination of valuable crops remain of great interest globally. The current study evaluated the effect of biostimulant (Kelpak® and plant-growth-promoting rhizobacteria-PGPR) biopriming on the seed germination of five (VI037996, VI046567, VI055421, VI050956, and VI033796) Abelmoschus esculentus genotypes. The germination responses of the bio-primed seeds were measured using six parameters, including final germination percentage (FGP), mean germination time (MGT), germination index (GI), coefficient of velocity of germination (CVG), germination rate index (GRI), and time spread of germination (TSG). Biostimulant application significantly affected MGT (1.1-2.2 days), CVG (1.4-5.9), and TSG (1.2-3.0 days). Genotype also significantly influenced the TSG (1-3 days). Significant interaction effect of biostimulant treatment and genotype was evident on the FGP, GI, and GRI of the germinated seeds. The most noteworthy effect was demonstrated by Kelpak® (1:100) applied to genotype VI037996, with significantly improved FGP (82%), GI (238), and GRI (77%/day) when compared to the control. Overall, the current findings suggest the potential stimulatory effect of biostimulants (especially Kelpak®) on the germination of Abelmoschus esculentus seeds. However, this influence was strongly dependent on the type of genotype.

Photochemistry and photoprotection of 'Gem' avocado (Persea americana Mill.) leaves within and outside the canopy and the relationship with fruit maturity.

A reduction in photosynthesis results in a reduced CO2 assimilation rate and availability of carbohydrates essential for fruit growth and development. This study determined photosynthetic efficiency and photoprotection mechanisms within and outside leaf canopy positions in 'Gem' avocado orchards and their relationship with avocado fruit maturity. The study was conducted in a commercial orchard at Everdon Estate in KwaZulu-Natal, South Africa. A total of 15 eight-year-old avocado trees (cv. Gem) were selected in a completely randomised design with three replicates, with each replicate consisting of five trees. Data were collected bi-weekly on photosynthetic rate (A), effective quantum efficiency of photosystem II (ϕPSII), stomatal conductance (gs), transpiration rate (T), electron transport rate (ETR), minimum fluorescence (Fo'), maximum fluorescence (Fm'), variable fluorescence (Fv'), intrinsic water use efficiency (WUEi), instantaneous water use efficiency (WUEins), intercellular CO2 concentration (Ci) and photochemical quenching (qP) from full bloom to fruit physiological maturity (∼25 % dry matter content (DM)). The results showed that leaves from the outside position had higher A (29.46 mol CO2 m-2s-1); gs (0.078 mol CO2 m-2s-1); ΦPS II (0.32); and qP (0.52) compared to those within the canopy position with lower A (19.27 mol CO2 m-2s-1); gs (0.0037 mol CO2 m-2s-1); ΦPS II (0.044) and qP (0.075), respectively. Contrastingly, chlorophyll fluorescence and photoprotection parameters were higher within the canopy than on the outside, suggesting that the greater proportion of energy accumulated within the canopy was used for photoprotection other than photochemistry. Photosynthetic rate (A), gs, Ci, T, WUEi and WUEins, correlated significantly with mesocarp dry matter (DM), while all other parameters correlated poorly. The high photosynthetic efficiency of leaves from outside the canopy resulted in an average DM of 28.9 % compared to 26.9 % of fruit within the canopy. The present findings suggest that reduced photosynthetic efficiency of 'Gem' avocado within the canopy position does not compromise fruit DM by reserving more energy for photoprotection; however, it delays maturity by about two weeks.

Model development for non-destructive determination of rind biochemical properties of 'Marsh' grapefruit using visible to near-infrared spectroscopy and chemometrics.

Rind biochemical properties play major roles in defence mechanisms against the incidence of rind physiological disorders of citrus fruit during cold storage. Hence, multivariate calibration models were developed to rapidly and non-destructively determine rind biochemical properties of citrus fruit from visible to near-infrared (Vis/NIR) spectra acquired by Vis/NIR spectroscopy using partial least square regression algorithm. To achieve optimum models for determination of each rind biochemical property, several mathematical pre-processing methods were explored, including no pre-treatment. However, special emphases were given to the best model statistics in terms of coefficient of determination (R2) and residual predictive deviation (RPD). Models were performed by critical examination of different wavelength ranges (visible, near-infrared and full regions) and combinations of fruit harvested from different production regions and acquired before (week 0) and after (week 9) cold storage. Results obtained showed excellent models for determining parameters such as sucrose (R2 = 0.99 and RPD = 11.42), total flavonoids (R2 = 0.99 and RPD = 12.37), and chlorophyll b (R2 = 0.97 and RPD = 5.67). This study reported the first application of Vis/NIR and chemometrics in determining the rind biochemical properties of 'Marsh' grapefruit rapidly and non-destructively.

Drought tolerance of selected bottle gourd [Lagenaria siceraria (Molina) Standl.] landraces assessed by leaf gas exchange and photosynthetic efficiency.

Successful cultivation of bottle gourd in arid and semi-arid areas of sub-Saharan Africa and globally requires the identification of drought tolerant parents for developing superior genotypes with increased drought resistance. The objective of this study was to determine the level of drought tolerance among genetically diverse South African bottle gourd landraces based on leaf gas exchange and photosynthetic efficiency and identify promising genotypes for breeding. The responses of 12 bottle gourd landraces grown in glasshouse under non-stressed (NS) and drought-stressed (DS) conditions were studied. A significant genotype x water regime interaction was observed for gs, T, A, A/Ci, IWUE, WUEins, Fm', Fv'/Fm', ФPSII, qP, qN, ETR, ETR/A and AES indicating variability in response among the studied bottle gourd landraces under NS and DS conditions. Principal component analysis identified three principal components (PC's) under drought stress condition contributing to 82.9% of total variation among leaf gas exchange and chlorophyll fluorescence parameters measured. PC1 explained 36% of total variation contributed by gs, T, F0', Fm', Fv'/Fm' and qN, while PC2 explained 28% of the variation and highly correlated with A, A/Ci, IWUE, WUEins ETR/A and AES. PC3 explained 14% of total variation contributed by ФPSII, qP and ETR. Principal biplot analysis allowed the identification of drought tolerant genotypes such as BG-27, BG-48, BG-58, BG-79, BG-70 and BG-78 which were grouped based on high gs, A, Fm'Fv'/Fm', qN, ETR/A and AES under DS condition. The study suggests that the identified physiological traits could be useful indicators in the selection of bottle gourd genotypes for increased drought tolerance.

Screening of Bread Wheat Genotypes for Drought Tolerance Using Phenotypic and Proline Analyses.

Drought stress is one of the leading constraints to wheat (Triticum aestivum L.) production globally. Breeding for drought tolerance using novel genetic resources is an important mitigation strategy. This study aimed to determine the level of drought tolerance among diverse bread wheat genotypes using agronomic traits and proline analyses and to establish correlation of proline content and agronomic traits under drought-stress conditions in order to select promising wheat lines for breeding. Ninety-six diverse genotypes including 88 lines from the International Maize and Wheat Improvement Center (CIMMYT)'s heat and drought nurseries, and eight local checks were evaluated under greenhouse and field conditions during 2014/15 and 2015/16 making four testing environments. The following phenotypic traits were collected after stress imposed during the heading to anthesis period: the number of days to heading (DTH), days to maturity (DTM), productive tiller number (TN), plant height (PH), spike length (SL), spikelet per spike (SPS), kernels per spike (KPS), thousand kernel weight (TKW) and grain yield (GY) and proline content (PC). Analysis of variance, Pearson's correlation coefficient, principal component and stress tolerance index were calculated. Genotypes with high yield performance under stressed and optimum conditions maintained high values for yield components. Proline content significantly increased under stress, but weakly correlated with agronomic traits under both optimal and water limited conditions. The positive correlation observed between grain yield and proline content under-drought stress conditions provides evidence that proline accumulation might ultimately be considered as a tool for effective selection of drought tolerant genotypes. The study selected 12 genotypes with high grain yields under drought stressed conditions and favorable adaptive traits useful for breeding.