Fungitoxicity of some fungicides against to pathogens responsible of olive trees decline in the Chebika’s area in Tunisia

The incidence of the disease seems very important on young trees and tends to bemoderate with the aging of the tree. In fact, olive trees have a shallow root system and arestill vulnerable to pathogens especially the irrigated varieties. Chemical and biological control against Fusarium solani, Fusarium oxysporum, Rhizoctonia solani and Verticillium dahliae have revealed that the application in vitro of Prodazim and of Methyl-thiophanatehave showed a very good efficacy up to 100%. Ridomil and Tachigaren have indicated aregular efficiency, while the two bio-fungicides Fungstop and the compost juice havedemonstrated a low efficiency. The two bio-control agents Trichoderma harzianum and Gliocladium virens have showed a relatively high effectiveness in vitro. In vivo, obtainedresults have revealed that the nature of the product, the doses applied and the condition ofthe olive trees are highly correlated factors. The treatment doesn’t appear to have apositive effect on the beginning of stage 1 and on plots presented a good structured soil.Going beyond this stage, whatever the product and the doses used, the attack isirreversible

Effects of crop sequences on soil population dynamics of Monosporascus cannonballus ascopsores and Monosporascus root rot and vine decline incidence

[EN] Crop sequences effect on the soil population dynamics of Monosporascus cannonballus ascospores and the incidence of Monosporascus root rot and vine decline (MRRVD), was investigated in a field in which three different cucurbit crops: melon, watermelon, and watermelon grafted onto Cucurbita rootstock, and tomato, were grown during two consecutive growing seasons. Cultivation of melon or watermelon crops in the first growing season resulted in an increase of soil ascopore densities. But, on the contrary, the soil ascospore densities in the second growing season were lower when grafted watermelon or tomatos were cultivated in the first growing season. In the second growing season, MRRVD incidence for each cucurbit crop was significantly different depending on the previous crop, being in general higher when melon or watermelon were the previous crops, slightly lower when the previous crop was grafted watermelon and the lowest when the previous crop was tomato. Disease incidence corresponded with the percentage of isolation of M. cannonballus from the roots, being always significantly lower when the previous crop was tomato. These results demonstrate the potential of crop rotation as a management strategy to reduce infection and reproduction of M. cannonballus, ascospore densities in soil and disease incidence in cucurbits.Ben Salem, I.; M'hamdi, M.; Armengol Fortí, J.; Boughalleb-Mhamdi, N. (2015). Effects of crop sequences on soil population dynamics of Monosporascus cannonballus ascopsores and Monosporascus root rot and vine decline incidence. International Journal of Current Microbiology and Applied Sciences (Online). 4(9):482-500. http://hdl.handle.net/10251/89413S4825004

Development of a screening test for resistance of cucurbits and Cucurbita hybrid rootstocks to Monosporascus cannonballus

[EN] Screening test resistance of cucurbit plants to Monosporascus cannonballus, responsible of Monosporascus root rot and vine decline was developed. Inocula of two isolates were grown in wheat seeds medium and served for pathogenicity test on watermelon (cv. Charleston gray) using 5 inoculum densities (50, 100, 150, 200 and 250 g of infected wheat seeds/kg of peat). Disease severity was evaluated based on root disease index (RDI), plant height (PH), shoot and root fresh and dry weights (SFW, RFW, SDW, and RDW). Significant differences in RDI records were noted among the 5 inoculum densities tested as compared to the non-inoculated control, and they were negatively correlated with PH, TDW and RDW. Pathogenicity tests on Armenian cucumber (Fakous), muskmelon (cvs. Flamengo and Dziria), watermelon (cv. Charleston gray), and two Cucurbita maxima x C. moschata rootstocks (cvs. Strongtoza and Emphasis), were conducted at the inoculum density of 200 g of inoculum/kg of peat. Characteristic symptoms of the disease were reproduced and the range of responses to M. cannonballus corresponded to those reported by previous research. Watermelon was susceptible to the pathogen, while Cucurbita hybrid rootstocks were the most tolerant. Evaluation of the resistance to M. cannonballus of eight Cucurbita hybrid rootstocks was conducted in a greenhouse experiment with 200 g of inoculum/kg of peat. All rootstocks evaluated seemed to response similarly for the RDI. However, no significant difference was noted for the other evaluated parameters.[FR] Un test de criblage de la résistance des plants de cucurbitacées à Monosporascus cannonballus, responsable du dépérissement a été développé. Deux isolats ont été cultivés sur des grains de blé et ont servi pour le test de la pathogénie sur la pastèque (cv. Charleston gray) selon 5 densités d¿inoculum (50, 100, 150, 200 et 250 g de grains de blé infectés/kg de tourbe). La sévérité de la maladie a été évaluée selon un indice de maladie racinaire (RDI), la hauteur de la plante (HP), les poids frais (SFW et RFW) et secs (SDW et RDW) des parties aérienne et racinaire. Une différence significative a été notée selon l¿indice RDI entre les 5 densités d'inoculum par rapport au témoin, et une corrélation négative avec la réduction des paramètres HP, SDW et RDW a été obtenue. Les tests de pathogénie sur trois espèces de cucurbitacées: concombre arménien (Fakous), melon (cvs. Flamengo et Dziria), pastèque (cv. Charleston gris) et deux porte-greffes Cucurbita maxima x C. moschata (cvs. Strongtoza et Emphasis), ont été effectuées à la densité de 200 g d'inoculum/kg de tourbe. Les symptômes caractéristiques de la maladie ont été reproduits et la gamme des réponses à M. cannonballus correspondaient à ceux rapportés dans la littérature. La pastèque s¿est montrée sensible à cet agent pathogène, tandis que les porte-greffes hybrides du genre Cucurbita étaient les plus tolérants. Un autre essai de la résistance à M. cannonballus a été réalisé sur huit porte-greffes hybrides du genre Cucurbita en culture sous serre avec 200 g d¿inoculum/kg de tourbe. Tous les porte-greffes paraissent réagir de la même façon concernant l¿indice RDI et des différences non significatives pour les autres paramètres évalués ont été notées.Ben Salem, I.; Armengol Fortí, J.; Berbegal Martinez, M.; Boughalleb-Mhamdi, N. (2015). Development of a screening test for resistance of cucurbits and Cucurbita hybrid rootstocks to Monosporascus cannonballus. Tunisian Journal of Plant Protection. 10(1):23-33. http://hdl.handle.net/10251/101851S233310

Morphological and Biological Characterization of Monosporascus cannonballus isolates, responsible of watermelon decline in Kairouan's area

Watermelon grown in Kairouan's region is infected by vine decline disease caused by M. cannonballus. In vitro tests showed that this pathogen produces perithecia with a diameter of 495 μm releasing ascospores with a diameter of 44 μm. The mycelium is very fine, rarely visible in the media KOMADA and TANAKA. The colony of different isolates on substrate culture such as Malt, MS and S, appears very dense. On PDA, the grayish brown color characteristic of this ascomycete was observed. The perithecia production in vitro test for this fungus requires relatively long period of incubation (45 days). The effect of culture media showed that the PDA, MS and Malt are the best for the mycelia development of M. cannonballus. The most favorable culture media for fructification arein descending order MS, S, PDA, Malt. M. cannonballus isolates tested in this study showed an optimum temperature of mycelial growth and reproduction of 30°C. MT15 andMT12 isolates originated from Chebika (Kairouan government) showed a significantmycelial growth at all temperatures of incubation. MT7 and MT14 isolates from the sameregion were the most fertile. The results of pH effect on M. cannonballus developmenthave revealed that the maximum mycelial growth occurred at pH 6 for most of isolates andfor the fructification occurred at pH 4 and pH 8. For the osmotic pression with the addition of NaCl and KCl, the optimal development for majority of isolates is registeredat -0.5 MPa and -2 MPa, with a minimum at -4MPa. The inhibition of the fructification of the M. cannonballus isolates occurred beyond -2MPa

Screening of fungi implicated in the dieback of olive trees (Olea europea) in Chebika’s area

Several surveys were conducted during spring 2008 in Chebika’s area in Tunisia. Samples were collected from infected plants showed different types of symptoms and they have been the subject of mycological analysis. The morphological identification of fungal colonies isolated from roots, crown and stems of two olive varieties Koroneiki and Chemlali Sfax, revealed the presence of a fungi complex including Fusarium oxysporum, Fusarium solani, Rhizoctonia solani, Verticillium dahliae, Cladosporium fulvum, Alternaria solani, Alternaria tenuis, Bispora punctata. and Cylindrocarpon .sp; Although,those fungi Fusarium oxysporum, Fusarium solani, Rhizoctonia solani and Verticillium dahliae are ubiquitous and the predominant one. Pathogenicity results revealed that the fungi isolated from olive trees exhibited typical symptoms on Koroneiki variety incontrolled conditions

Antifungal Activity of Volatile Components Extracted from Leaves, Stems and Flowers of Four Plants Growing in Tunisia

Volatile components extracted from the leaves, stems and flowers of Lantana camara, Malvaviscus arboreus, Hibiscus rosa-sinensis cv. red flowers and white flowers were tested against the fungi Alternaria solani, Botrytis cinerea, Fusarium solani f. sp. cucurbitae, F. oxysporum f. sp. niveum, Pythium ultimum, Rhizoctonia solani and Verticillium dahliae. The strongest inhibitory effect of the extracts was found with volatile components extracted from the stems and the flowers. Complete inhibition was achieved against V. dahliae. The weakest effect was against P. ultimum. Volatile components extracted from the leaves were not effective

Diversity of the Pythium community infecting crown and roots apple in Tunisia

The genus Pythium is important in agriculture, since it contains many plant pathogenic species. Little is known about the diversity of Pythium species causing apple dicline. Therefore, the aim of the study was to characterize 21 Pythium isolates collected from root and collar rot apple trees in Tunisia from 2006 through to 2009. The isolates were characterized morphologically as well as through sequence analyze of the internal transcribed spacer region (ITS). Three Pythium species were identified in this study P. rostratifingens, P. undulatum and P. sterilum. In virulence assays on excised apple twigsand in the fields, representative isolates of the different Pythium species isolated were pathogenic on the Anna, Lorka and Meski varieties and the MM106 rootstock. Results obtained show the great susceptibility of the MM106 rootstock to the infections for the different Pythium species tested

Resistencia aumentada a Rhizoctonia solani por la expresión combinada de quitinasa y proteínas inactivantes de los ribosomas en patatas transgénicas

Potato (Solanum tuberosum L.) is susceptible to many fungal pathogens including Rhizoctonia solani. In the present study, the potato cultivar Desirée was transformed via Agrobacterium tumefaciens strain GV3101 containing the binary plasmid pGJ132 harboring both the chitinase (chiA) and rip30 genes. The potato leaf disc was used as an explant for transformation. PCR, Southern blot and Western blot were used for characterization of the transgenic plants. In this study it was shown that not all the plants developed in selective medium were positive for the corresponding gene using the PCR technique. Southern blot analysis confirmed that transgenic plants integrated 2-3 copies of chiA and rip30 genes respectively into their genome. The expression of the CHIA and RIP30 proteins was confirmed in the leaf extracts of the transgenic clones by Western blot analysis. Transgenic potato plants expressing rip30 and chiA genes showed enhanced resistance to R. solani in a greenhouse assay.La patata (Solanum tuberosum L.) es susceptible a muchos hongos fitopatógenos, incluyendo Rhizoctonia solani. En el presente estudio, se transformó el cultivar de patata ‘Desirée’ mediante Agrobacterium tumefaciens, cepa GV3101, que contiene el plásmido binario pGJ132 que alberga los genes quitinasa (chiA) y rip30. Se utilizaron discos de hojas como explante para la transformación de plantas. Se utilizaron las técnicas de PCR, Southern y Western blot para la caracterización de las plantas transgénicas. En este estudio se demostró, mediante PCR, que no todas las plantas que se desarrollaron en medio selectivo fueron positivas para el gen correspondiente. El análisis de Southern blot confirmó que las plantas transgénicas integraron en su genoma 2-3 copias de los genes chiA y rip30. Se llevó a cabo un ensayo de invernadero para evaluar la resistencia a R. solani de los clones transgénicos que expresan los transgenes. Las plantas transgénicas que expresan los genes rip30 y chiA mostraron una resistencia completa a R. solani

Ribosome Inactivating Protein of barley enhanced resistance to Rhizoctonia solani in transgenic potato cultivar 'Desirée' in greenhouse conditions

In the present study, the potato cultivar 'Desirée' was transformed via Agrobacterium tumefaciens strain LBA4404 containing the plasmid pBIN19 which harbors the Ribosome Inactivating Protein (rip30). The potato leaf discs were used as an explant for transformation. The in vitro regeneration parameters (percentage of callus regenerated, number of shoots per callus, percentage of regenerated roots and percentage of the transgenic plants) were evaluated. The PCR technique was used for identification of transformed plants. Southern and Western blot analyses were applied for molecular characterization of the transgenic clones. A greenhouse assay was carried out to evaluate the resistance to Rhizoctonia solani pathogen of transgenic clones expressing the rip30 gene. The results revealed that not all the plants developed in selective medium were positive for the corresponding gene using the PCR technique. Southern blot analysis demonstrated that the tested transgenic plants integrated three copies of rip30 gene into their genome. The expression of the RIP30 protein was confirmed in the leaf extracts of the transgenic clones by Western blot analysis. Resistance evaluation of the transgenic plants in greenhouse conditions showed that disease incidence and severity were reduced for R. solani