Evolutionary and Experimental Assessment of Novel Markers for Detection of Xanthomonas euvesicatoria in Plant Samples

BACKGROUND: Bacterial spot-causing xanthomonads (BSX) are quarantine phytopathogenic bacteria responsible for heavy losses in tomato and pepper production. Despite the research on improved plant spraying methods and resistant cultivars, the use of healthy plant material is still considered as the most effective bacterial spot control measure. Therefore, rapid and efficient detection methods are crucial for an early detection of these phytopathogens. METHODOLOGY: In this work, we selected and validated novel DNA markers for reliable detection of the BSX Xanthomonas euvesicatoria (Xeu). Xeu-specific DNA regions were selected using two online applications, CUPID and Insignia. Furthermore, to facilitate the selection of putative DNA markers, a customized C program was designed to retrieve the regions outputted by both databases. The in silico validation was further extended in order to provide an insight on the origin of these Xeu-specific regions by assessing chromosomal location, GC content, codon usage and synteny analyses. Primer-pairs were designed for amplification of those regions and the PCR validation assays showed that most primers allowed for positive amplification with different Xeu strains. The obtained amplicons were labeled and used as probes in dot blot assays, which allowed testing the probes against a collection of 12 non-BSX Xanthomonas and 23 other phytopathogenic bacteria. These assays confirmed the specificity of the selected DNA markers. Finally, we designed and tested a duplex PCR assay and an inverted dot blot platform for culture-independent detection of Xeu in infected plants. SIGNIFICANCE: This study details a selection strategy able to provide a large number of Xeu-specific DNA markers. As demonstrated, the selected markers can detect Xeu in infected plants both by PCR and by hybridization-based assays coupled with automatic data analysis. Furthermore, this work is a contribution to implement more efficient DNA-based methods of bacterial diagnostics

Yield and chemical composition of essential oil of Mentha piperita var. multimentha grown under different agro-ecological locations in Egypt

This investigation was carried out during two successive seasons to evaluate the growth productivity and oil quality of Mentha piperita var. Multymentha grown in four different locations in Egypt (El-Sharkia, El-Fayoum, Ismailia and North Sinai). The obtained results refer to presence of high significant differences between locations under study and a positive correlation could be observed between the yield of Mentha plants and temperate climate conditions. The samples from El-Fayoum location showed the highest record for all growth parameters than other locations. On the other hand, there is a great variability in the yield of essential oils where the EO ranged from 0.285 to 1.240% according to the agro-ecological region of cultivation. The chemical composition of EOs obtained from different locations are characterized by high menthone/menthol contents and high antioxidant activity especially in the plants grown in El-Fayoum and Ismailia which could be attributed to their high amount of phenolic compounds and flavonoids comparing to other locations. The amount of oxygenated compounds in the EOs is high in the warmer locations (El-Fayoum 89.62%), while the amount of sesquiterpene hydrocarbons was found to be high in El-Sharkia locations (6.68%). Cultivation of Mentha piperita var. Multymentha in different Egyptian locations characterized by different geographical and weather conditions, affected the quantities of the major components in a statistically significant way

Interactive effects of salinity and silicon application on Solanum lycopersicum growth, physiology and shelf‐life of fruit produced hydroponically

BACKGROUND Using water with high salinity for plant fertigation may have detrimental effects on plant development and total yield and on the quality of the crop produced. As a possible means to alleviate the negative effects of salinity, silicon (Si) can be incorporated in the nutrient solution supplied to plants. In the present study, hydroponically grown tomato (Solanum lycopersicum Mill.) plants were subjected to two different salinity levels (0 and 50 mmol L-1 NaCl) with and without the application of Si (0 and 2 mmol L-1 K2SiO3) in order to evaluate its possible positive impact on mitigation of salinity stress-induced symptoms. An additional experiment was implemented with postharvest Si application (sodium silicate) to investigate effects on the shelf-life of tomato fruit. RESULTS Salinity (50 mmol L-1 NaCl) decreased plant size, total yield and fresh fruit weight while a high percentage of blossom end rot symptoms of tomato fruit was also observed. The application of Si in the nutrient solution counteracted these detrimental effects, generating a higher yield and healthier fruit (lower blossom end rot incidence) compared to the untreated plants (no application of Si). Salinity improved several quality-related traits in tomato fruit, resulting in higher marketability, whereas the addition of Si (pre- and postharvest) maintained fruit firmness following storage thereby increasing the shelf-life of tomato fruit. CONCLUSIONS These findings indicate that Si application (pre- and postharvest) could provide an effective means of alleviating the unfavorable effects of using low-quality water in plant fertigation on tomato plant development, fruit yield and post-harvest quality, through increased fruit firmnes