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Watermelon Sudden Decay in Tunisia: Identification of Pathogenic Fungi and Determination of Primary Agents
Naima Boughalleb,Mohamed El Mahjoub
Pakistan Journal of Biological Sciences , 2006,
Abstract: Isolation from infected watermelon samples has demonstrated the presence of some fungal complex including Fusarium oxysporum, F. solani, Rhizoctonia bataticola, R. solani, Monosporascus cannonballus, Pythium ultimum and P. echinulatum. These fungal species are different in their distribution among the infected plants and areas surveyed. However, F. oxysporum and F. solani are always predominant. These results showed the almost-presence of the two Fusarium disease of watermelon: Fusarium wilt to F. oxysporum f. sp. niveum and the collars and/or root rot caused by F. solani f. sp. cucurbitae which are the primary fungi of sudden wilt. Analysis in main component of isolation frequency of different fungi showed that their association in homogeneous groups seemed not affected by geographic origin and surveyed year.
Evaluation of Genetic Diversity in Aegilops geniculata Roth Accessions using Morphological and RAPD Markers
A. Mahjoub,Mohamed Salah El Gharbi,K. Mguis,Mohamed El Gazzah
Pakistan Journal of Biological Sciences , 2009,
Abstract: Thirteen Aegilops geniculata Roth (geniculate goat grass) accessions from collection of the North and Central Tunisian (Cap-Bon, Mogodses, Kroumiry and the Dorsal areas) were used to assess its genetic diversity by morphological and Random Amplified Polymorphic DNA (RAPD) data and to evaluate relationship between morphological and RAPD markers. Nineteen morphological traits were analyzed on all accessions using Principal Analysis Component (PCA) and clusters were constrained based on median joining distances. Nineteen arbitrary universal primers were used for the amplification of random DNA sequences and generated 212 bands ranging from 0.5 to 3 kb with 71.27% polymorphism across the 13 accessions. Both RAPD and morphological data classified accessions in two main groups. Both methods were used to compare how morphological traits and RAPD molecular markers described accessions relationship and showed a high degree of variation among analyzed accessions, indicating an important source of genetic diversity that can be used in future breeding programs. Morphological PCA traits and cluster indicated climatic stage. In fact, they grouped Ae. geniculata accessions according to genetic criteria such as earliness and high kernel yield. Comparison of morphological and molecular data using the Mantel test indicated a non significant correlation (r = -0.268). Nevertheless, RAPD and selected morphological characters appear as useful and complementary techniques for evaluation of genetic diversity in Ae. geniculata.
Temperature Effect on Mycelial Growth and on Disease Incidence of Fusarium oxysporum f.sp. radicis-lycopersici
Khaled Hibar,Mejda Daami-Remadi,Hayfa Jabnoun-Khiareddine,Mohamed El Mahjoub
Plant Pathology Journal , 2006,
Abstract: Fusarium crown and root rot of tomato (Lycopersicon esculentum) caused by Fusarium oxysporum f.sp. radicis-lycopersici is a new damaging disease of greenhouse crops in Tunisia. This pathogen was detected in Southern Tunisia, where temperature is usually high. Thus, temperature effect on its development was studied in vitro, on mycelial growth and in vivo, on disease incidence. Temperature effect on mycelial growth of Fusarium oxysporum. sp. radicis-lycopersici, evaluated on Potato Dextrose Agar (PDA) media, revealed that this pathogen grows well at temperatures ranged from 20 to 30°C. However, the optimum of mycelial growth was recorded at 25°C (growth speed exceeded 13 mm D-1). On disease incidence, temperature effect was evaluated by breeding inoculated plants under two thermal conditions: 19 and 29°C. Damages observed, after an incubation period ranged between 30 and 50 days, were more important at 19°C than that at 29°C. Indeed, at 19°C, disease incidence exceeded 96% and it was always more than 70%. At 29°C, however, this value didn`t exceed 60% and this by using two inoculation methods.
Potato Vascular Fusarium wilt in Tunisia: Incidence and Biocontrol by Trichoderma spp.
Fakher Ayed,Mejda Daami-Remadi,Hayfa Jabnoun-Khiareddine,Mohamed El Mahjoub
Plant Pathology Journal , 2006,
Abstract: Pathogen isolations from potato tubers showing dry rot symptoms revealed the presence of Fusarium oxysporum f. sp. tuberosi in different Tunisian regions. Pathogenicity tests of different isolates were realized on potato plants. Typical symptoms of vascular wilt disease were observed and noted. After wilting, inoculated plants were totally damaged. Trichoderma spp. were evaluated for their antagonistic potential against F. oxysporum f. sp. tuberosi in vitro and in vivo. Trichoderma harzianum, T. viride and T. virens inhibited the mycelial growth of F. oxysporum f. sp. tuberosi. The antagonism included lysis and dissolution of the host cytoplasm and/or transformation into cords and/or coiling around pathogen hyphae. Moreover, substrate application of Trichoderma species (108 spores per mL) before inoculation by F. oxysporum f. sp. tuberosi controlled Fusarium wilt of potato plants compared with non-inoculated plants and untreated-inoculated plants. This approach may be beneficial for biological control in F. oxysporum f. sp. tuberosi and could allow protecting plants from this pathogen.
Control of Fusarium Crown and Root Rot of Tomato, Caused by Fusarium oxysporum f. sp. radicis-lycopersici, by Grafting onto Resistant Rootstocks
Khaled Hibar,Mejda Daami-Remadi,Hayfa Jabnoun-Khiareddine,Mohamed El Mahjoub
Plant Pathology Journal , 2006,
Abstract: In this study, the efficacy of grafting two tomato cultivars onto two rootstocks was examined in growth chamber and in greenhouse conditions. The rootstock cultivars Beaufort F1 and He-Man F1, already known and confirmed as resistant to Fusarium oxysporum f. sp. radicis-lycopersici, were evaluated during two crop seasons under greenhouse heated with geothermal water in South Tunisia. The cv. Durintha F1 showed the best plant growth, fruit yield and fruit quality when grafted onto Beaufort F1; while cv. Bochra F1 gave the best results when grafted onto He-Man F1. This study demonstrated that grafting tomato cultivars onto Fusarium resistant rootstocks is one of the best alternatives for controlling Fusarium crown and root rot of tomato.
Unsupervised image segmentation by Global and local Criteria Optimization Based on Bayesian Networks
Mohamed Ali Mahjoub,Mohamed Mhiri
Computer Science , 2015,
Abstract: Today Bayesian networks are more used in many areas of decision support and image processing. In this way, our proposed approach uses Bayesian Network to modelize the segmented image quality. This quality is calculated on a set of attributes that represent local evaluation measures. The idea is to have these local levels chosen in a way to be intersected into them to keep the overall appearance of segmentation. The approach operates in two phases: the first phase is to make an over-segmentation which gives superpixels card. In the second phase, we model the superpixels by a Bayesian Network. To find the segmented image with the best overall quality we used two approximate inference methods, the first using ICM algorithm which is widely used in Markov Models and a second is a recursive method called algorithm of model decomposition based on max-product algorithm which is very popular in the recent works of image segmentation. For our model, we have shown that the composition of these two algorithms leads to good segmentation performance.
Les oasis de l'Oued Noun: dégradation du milieu naturel et perspectives de développement
EL MAHJOUB CHMOURK
Cinq Continents , 2011,
Abstract: The oases of Oued Noun: degradation of the natural environment andperspectives of development. An oasis is considered as a vital space and a fundamental natural resource in the Oued Noun area. Irrigation water scarcity, desertification, terminal illnesses of different civilizations, space division and tininess of farms are all natural and economic constraints providing the oasis area from growing and developing. Officials have to be aware of those constraintsand they need to urgently recommend solutions in the process of updating the local territory and in its potentialities valorisation.
Le Sahara marocain : désenclavement et développement durable
EL MAHJOUB CHMOURK
Cinq Continents , 2012,
Abstract: Theenclosing of the Moroccan Sahara results from the inversion and old situation.Indeed, during a very long time, the area was a way of passage, a platform in thesouth of Morocco. In testify the Tran-Saharan commercial routes, which were themain transportation routes back in time, like the goal of integration of the area inthe country and compared to western Africa. It is with the economic crisis, and even a political crisis causing a fold on itself of this area until 1975.Since Sahara belongs to Morocco, it still profits a considerable public effort to carry out its opening-up and its economic insertion within the country. Massive investmentscarried out by the State give to the area the structuring which it missed. Which are the aspects of the Sahara development? Which role played the State in this development? The intervention of the State contributes to bring effectivesolutions to the problem of the opening-up of this surrounding space?
New approach using Bayesian Network to improve content based image classification systems
Khlifia Jayech,Mohamed Ali Mahjoub
International Journal of Computer Science Issues , 2010,
Abstract: This paper proposes a new approach based on augmented naive Bayes for image classification. Initially, each image is cutting in a whole of blocks. For each block, we compute a vector of descriptors. Then, we propose to carry out a classification of the vectors of descriptors to build a vector of labels for each image. Finally, we propose three variants of Bayesian Networks such as Naive Bayesian Network (NB), Tree Augmented Naive Bayes (TAN) and Forest Augmented Naive Bayes (FAN) to classify the image using the vector of labels. The results showed a marked improvement over the FAN, NB and TAN.
Clustering and Bayesian network for image of faces classification
Khlifia Jayech,Mohamed Ali Mahjoub
Computer Science , 2012,
Abstract: In a content based image classification system, target images are sorted by feature similarities with respect to the query (CBIR). In this paper, we propose to use new approach combining distance tangent, k-means algorithm and Bayesian network for image classification. First, we use the technique of tangent distance to calculate several tangent spaces representing the same image. The objective is to reduce the error in the classification phase. Second, we cut the image in a whole of blocks. For each block, we compute a vector of descriptors. Then, we use K-means to cluster the low-level features including color and texture information to build a vector of labels for each image. Finally, we apply five variants of Bayesian networks classifiers (Na\"ive Bayes, Global Tree Augmented Na\"ive Bayes (GTAN), Global Forest Augmented Na\"ive Bayes (GFAN), Tree Augmented Na\"ive Bayes for each class (TAN), and Forest Augmented Na\"ive Bayes for each class (FAN) to classify the image of faces using the vector of labels. In order to validate the feasibility and effectively, we compare the results of GFAN to FAN and to the others classifiers (NB, GTAN, TAN). The results demonstrate FAN outperforms than GFAN, NB, GTAN and TAN in the overall classification accuracy.
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