IDENTIFICACIÓN DE MICROORGANISMOS PATÓGENOS EN EL CULTIVO DE (Stevia Rebaudiana Bertoni)

En campos comerciales de Stevia rebaudiana localizados en los centro poblados Las Palmas y Esperanza la se determinó la incidencia y severidad de enfermedades ocasionales por microorganismos patógenos. La investigación se desarrolló en fases de reconocimiento de la sintomatología, identificación de agentes causales y determinación de pruebas de patogenicidad. Se encontraron 8 hongos, como agentes causales de los marchitamientos, necrosis de la raíz, manchas foliares y necróticas. 8 hongos, Fusarium sp., Rhizoctonia sp., Sclerotinia sclerotiorum, Sclerotium rolfsii. Cuyos daños ocasionan en los tallos y raíces, Septoria sp., Cercospora sp., Alternaria sp., Oidium. La Esperanza se ha encontrado más plantas infestadas por una mayor diversidad de microorganismos. Los microorganismos no mostraron preferencias entre hojas y tallos y raíz. Para ambas zonas los microorganismos con mayor presencia fueron. Fusarium, Septoria y Sclerotinia sclerotiorum, Sclerotium rolfsii.

Trichoderma juruarense sp. nov. (Hypocreaceae) a new fungal species from sediments of the Amazonian Juruá River with agricultural potential

The species of Trichoderma are the most common fungi to be used as biocontrol agents, and their metabolic arsenal has a wide variety of applications that places this genus among those with the potential to provide biotechnological products. The ubiquitous nature of Trichoderma has favored a rapid increase in the number of described species, and significant efforts have been made towards the taxonomy of Trichoderma in order to improve the accuracy of identification. During a study of cultivable microbiota from the Juruá River, Amazon, Brazil. Isolates with morphological characteristics of the genus Trichoderma were screened for their capacity to control phytopathogens. A total of five Trichoderma isolates were identified using morphological data combined with phylogenetic analysis of the ITS region, and partial sequences of TEF and RPB2. Trichoderma juruarense sp. nov. form a monophyletic clade that is closely related to T. cyanodichotomus, a species that occupies an unresolved position in the Trichoderma taxonomy. T. cyanodichotomus and T. juruarense sp. nov. present an intracellular blue-green pigment in potato dextrose agar (PDA) and differ in conidia and chlamydospores sizes. These data support the proposition of a new species, named here as Trichoderma juruarense. The holotype of T. juruarense INPA0108 presents in vitro inhibition against phytopathogens, such as Colletotrichum siamense (50%), Corynespora cassiicola (43%), Fusarium decemcellulare (61%) and Sclerotium rolfsii (51%), which demonstrates desirable traits that warrant further studies on plant protection. In addition, T. cyanodichotomus and T. juruarense formed a new clade based on the sequence data of the RPB2 gene.

Plant Growth-Promoting Bacteria Associated with the Nests of the Seed-Harvester Ant, Trichomyrmex Scabriceps

Colonies of seed harvester ants are commonly found in semiarid and arid areas of the world and have been studied for their seed dispersal behaviour. The present study focused on the bacteria associated with the nests of the harvester ant, Trichomyrmex scabriceps, and reveals that ant colonies link the aboveground resources with the belowground microbial communities as they accumulate organic debris in the close vicinity of their nests via their ecosystem engineering activities. Soil samples were collected from the nest chambers and the external debris piles of T. scabriceps colonies, located in managed ecosystems. The nest soil-associated bacteria were examined for their plant growth-promoting abilities via biochemical assays including phosphate solubilization, Indole acetic acid production, siderophore production and physiological assays including biocontrol potential against the soil pathogen, Sclerotium rolfsii. More than 60% of bacteria isolated from the ant nest-associated soil displayed plant-growth promoting ability. Bacillus sp., Azotobacter sp., Klebsiella sp., Comamonas sp., Tsukamurella sp., and Pseudoxanthomonax sp., demonstrated significantly high levels of gnotobiotic growth of the treated chickpea plants. The activities of phenylalanine ammonia-lyase and peroxidase enzymes were higher in plant growth-promoting bacteria treated and pathogen inoculated plants as compared to the control plants lacking the bacteria. Since T. scabriceps colonies often make their nests in the compact soil of unpaved paths of agroecosystems and gardens, these bacteria can act as highly effective biofertilizers and promote growth of the cultivated plants by increasing soil fertility and disease resistance attributes of the plant.

Forecasting model for disease risk period in chickpea x collar rot pathosystem

Collar rot caused by Sclerotium rolfsii Sacc. is one of the major biotic constraints of chickpea production worldwide. It is soil-borne fungi having wider host range and infection mainly occurs at the juvenile stage of crop growth resulting crop failure in no time. The pathogen is greatly influenced by soil temperature (ST) and soil moisture (SM) therefore, experiment formulated to develop a suitable forecasting model for its future use in computer simulation of plant disease prognostication by feeding only soil temperature and moisture data. The popular desi type chickpea variety Anuradha sown at different dates to get a range of soil temperature and soil moisture combination and its corresponding effect on disease incidence was recorded under natural epiphytotic conditions. The data obtained were analyzed using binary logistic regression and discriminant analysis to assess disease risk and non-risk period. The model developed was Y'= -73.9 + 1.251 SM + 0.017 ST. The outcome recorded, a unique statistically significant contribution of soil moisture (p value=0.029) on the establishment of the disease whereas, the effect of soil temperature was detected as statistically non-significant. The model developed and the correctness of the model determined to predict the disease severity with 80 % accuracy.

Formula padat Bacillus cereus STRAIN TLE1.1 untuk pengendalian penyakit busuk pangkal batang (Sclerotium rolfsii) pada tanaman tomat

Penyakit utama tanaman tomat yaitu busuk pangkal batang yang disebabkan oleh Sclerotium rolfsii dapat menimbulkan kerugian mencapai 80-100%. Tujuan penelitian yaitu untuk mendapatkan formula padat Bacillus cereus strain TLE1.1 yang efektif untuk pengendalian penyakit busuk pangkal batang pada tanaman tomat. Penelitian bersifat eksperimen dengan mengamati kemampuan formula padat B. cereus strain TLE1.1 dalam pengendalian penyakit busuk pangkal batang dengan Rancangan Acak Lengkap yang terdiri atas 9 perlakuan dan 3 ulangan. Perlakuan terdiri atas kombinasi bahan pembawa formula padat yang terdiri atas limbah padat ampas tebu, ampas tahu dan tongkol jagung, fungisida serta kontrol. Masing-masing formula padat B. cereus strain TLE1.1 diintroduksi pada benih dan bibit tomat. Hasil penelitian menunjukkan bahwa hampir semua formula mampu menekan penyakit busuk pangkal batang tanaman tomat. Formula terbaik dalam menurunkan penyakit busuk pangkal batang pada tanaman yaitu formula ampas tahu dan ampas tahu + tongkol jagung.Main disease of tomato plant, namely stem rot caused by Sclerotium rolfsii which can cause losses up to 80-100%. The aim of the study was to obtain a solid formula of Bacillus cereus strain TLE1.1 which was effective for controlling stem rot disease in tomato plant. This research was an experimental study to know the ability of the solid formula of B. cereus strain TLE1.1 in controlling stem rot disease which was carried out in a completely randomizeddesign consisting of 9 treatments and 3 replications. The treatment consistedof a combination of solid formula carriers consisting of sugarcane solid waste,tofu dreg and corncob, fungicides and controls. Each solid formula of B. cereus strain TLE1.1 was introduced into tomato seeds and seedlings. The results showed that almost all of the formulas were able to suppress stem base disease of tomato plants. The best formula that reduced stem rot in plants were the tofu dreg and tofu dreg + corncob formula.

Purification, Identification And Characterization of Nag2 N-Acetylglucosaminidase From Trichoderma Virens Strain Mango

Background: N -acetylglucosaminidase (NAGase) could liberate N -acetylglucosamine (GlcNAc) from GlcNAc-containing oligosaccharides. Trichoderma spp. is an important source of chitinase, particularly NAGase for industrial use. nag1 and nag2 genes encoding NAGase , are found in the genome in Trichoderma spp. The deduced Nag1 and Nag2 shares ~55% homology in Trichoderma virens. Most studies were focus on Nag1 and nag1 previously. Results: The native NAGase (TvmNAG2) was purified to homogeneity with molecular mass of ~68 kDa on SDS-PAGE analysis, and identified as Nag2 by MALDI/MS analysis from an isolate T. virens strain mango. RT-PCR analyses revealed that only nag2 gene was expressed in liquid culture of T. virens , while both of nag1 and nag2 were expressed in T. virens cultured on the plates. TvmNAG2 was thermally stable up to 60 o C for 2 h, and the optimal pH and temperature were 5.0 and 60-65 o C, respectively, using p -nitrophenyl- N -acetyl- β -D-glucosaminide ( p NP-NAG) as substrate. Using colloidal chitin as substrate, the end product catalyzed by TvmNAG2 was GlcNAc, based on HPLC and TLC analyses. The optimal temperature for TvmNAG2 to produce GlcNAc was 40 o C. TvmNAG2 possesses antifungal activity, inhibiting the mycelium growth of Sclerotium rolfsii . And it was resistant to the proteolysis by papain and trypsin. Conclusions: The native Nag2, TvmNAG2 was purified and identified from T. virens strain mango, as well as enzymatic properties. To our knowledge, it is the first report with the properties of native Trichoderma Nag2.