ABSTRACT Plant tissue culture techniques are useful for producing a large number of disease-free plant material. The aim of the present study was to determine the optimal nodal explant type (terminal, intermediate and basal) and cytokinins (6-benzyladenine and thidiazuron [TDZ] at concentrations of 0 to 3 mg L-1) for bud break and axillary shoot proliferation of Glycyrrhiza glabra L. The intermediate nodal explants were effective for the establishment of G. glabra aseptic culture when compared with terminal or basal nodal explants. The highest bud break (89%) and axillary shoot proliferation (eight shoots) were observed when the intermediate nodal explants were cultured on MS medium supplemented with 2 mg L-1 TDZ for 30 d. The best rooting medium was MS medium supplemented with naphthalene acetic acid (NAA) compared with indole acetic acid; NAA at 6 mg L-1 yielded 78% rooting and an average of 6.3 roots per plantlet. The regenerated plantlets were acclimatized, with a survival rate of 77.7%, when transferred to ex vitro conditions and showed no morphological abnormalities. Thus, the high percentage of bud break and rate of shoot proliferation and successful acclimatization established a simple and efficient micropropagation of G. glabra.

ABSTRACT Sweet potato (Ipomoea batatas [L.] Lam.) is an important food crop that is cultivated and consumed worldwide, and its nutritional value makes it especially important in developing countries. However, sweet potato plants produced using conventional vegetative propagation can be prone to several diseases, thereby hindering crop yield. Therefore, micropropagation techniques are useful for producing higher quality plant material. The aim of the present study was to determine the optimal medium formulation for the axillary shoot multiplication of single-node ‘Abees’ explants. The influences of cytokinins (6-benzyladenine [BA], kinetin, thidiazuron, and zeatin), gibberellic acid, phenylacetic acid, indole-3-butyric acid, silver nitrate, and oxalic acid, culture duration, and medium salt strength were investigated. Optimal proliferation was observed when shoots were cultured on half-strength MS medium that was supplemented with 2 mg L-1 BA and 100 mg L-1 oxalic acid for 2 wk, followed by culture on half-strength MS medium without plant growth regulators for 4 wk. In this medium, the greatest number of shoots (3.1) and total number of nodes (16.1) per explant were observed. All (100%) of the regenerated shoots were rooted and acclimatized, with a survival rate of 96% when transferred to ex vitro conditions and no morphological abnormalities.

ABSTRACT High-throughput phenotyping using spectral reflectance measurements offers the potential to provide more information for making better-informed management decisions at the crop canopy level in real time. The aim of this study was to investigate the suitability of hyperspectral reflectance measurements of the crop canopy for the assessment of biomass, nitrogen concentration, nitrogen uptake, relative chlorophyll contents, and yield in 2 peanut cultivars, Giza 5 and Giza 6. Peanuts were grown under field conditions and subjected to 3 doses of nitrogen fertilizer with or without the application of 2 bio-fertilizers, Bradyrhizobium spp. or plant growth-promoting rhizobacteria. Simple linear regression of normalized difference spectral indices and partial least square regression (PLSR) were employed to develop predictive models to estimate the measured parameters. The tested spectral reflectance indices were significantly related to all measured parameters with R2 of up to 0.89. The spectral reflectance index values differed at the same level of nitrogen fertilizer, as well as among the 3 levels of nitrogen fertilizer application for inoculation with Bradyrhizobium and co-inoculation with Bradyrhizobium and plant growth-promoting rhizobacteria. The calibration models of PLSR data analysis further improved the results, with R2 values reaching 0.95. The overall results of this study indicate that hyperspectral reflectance measurements monitoring peanut plants enable rapid and non-destructive assessment of biomass, nitrogen status, and yield parameters of peanut cultivars subjected to various agronomic treatments.

ABSTRACT Drip irrigation combined with split application of fertilizer nitrogen (N) dissolved in the irrigation water (i.e. drip fertigation) is commonly considered best management practice for water and nutrient efficiency. This research was conducted to study the influence of drip fertigation in combination with or without N fertilizers on vegetative growth, flowering quality, nutrients concentration in plants and soil fertility after the harvest of zinnia ( Zinnia elegans). A field experiment was conducted using a randomized complete block split plot design with two systems of drip irrigation (surface and subsurface drip irrigation) and 4 nitrogen rates (0, 30, 60, and 120 kg∙ha–1) as the main and split plots, respectively. The results revealed that vegetative growth rate, flowering characteristics , plant chemical contents, plant uptake and available soil from N, P, K, Fe, Mn, and Zn of zinnia increased significantly with increasing N level up to 120 kg∙ha–1. A similar trend was also found in the post-harvest soil fertility and nutrient uptake that approved the importance of drip fertigation with N fertilizers. Subsurface drip irrigation system was found to be more efficient than surface drip irrigation system to obtain maximum yield accompanied by the highest nutrients concentration in zinnia plants and soil fertility after harvest.