Dr. Md. Atiqur Rahman Khokon Associate Professor and Head Department of Plant Pathology Bangladesh Agricultural University Mymensingh - 2202 BANGLADESH
Abstract: Isothiocyanates (ITCs) are degradation products of glucosinolates in crucifer plants and have repellent effect on insects, pathogens and herbivores. In this study, we report that exogenously applied allyl isothiocyanate (AITC) induced stomatal closure in Arabidopsis via production of reactive oxygen species (ROS) and nitric oxide (NO), and elevation of cytosolic Ca2+.AITC-induced stomatal closures were partially inhibited by an inhibitor of NADPH oxidase and completely inhibited by glutathione monoethyl ester (GSHmee). AITC-induced stomatal closure and ROS production
were examined in abscisic acid (ABA) deficient mutant aba2-2 and methyl jasmonate (MeJA)-deficient mutant aos to elucidate involvement of endogenous ABA
and MeJA. Genetic evidences have demonstrated that AITC-induced stomatal closure required MeJA priming but notABApriming.These results raise the possibility that crucifer plants produce ITCs to induce stomatal closure, leading to suppression of water loss and invasion of fungi through stomata.
Abstract: Chitosan induced stomatal closure in wild type-plants and NADPH oxidase knock-out mutants (atrbohD atrbohF), and reactive oxygen species (ROS) production in wild-type guard cells. Closure and production were completely abolished by catalase and a peroxidase inhibitor. These results indicate that chitosan induces ROS production mediated by peroxidase, resulting in stomatal closure
Abstract: Yeast elicitor (YEL) induces stomatal closure. We investigated reactive oxygen species (ROS) production, nitric oxide (NO) production and [Ca 2 + ] cyt oscillations to clarify YEL signaling in Arabidopsis guard cells. YEL induced ROS accumulation in guard cells. A peroxidase inhibitor [salicylhydroxamic acid (SHAM)] inhibited the stomatal closure and the ROS accumulation, but neither the atrbohD atrbohF mutation nor an NADPH oxidase inhibitor [diphenylene iodonium chloride (DPI)] had any effect. An NO scavenger [2-(4-
carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (cPTIO)] inhibited the YEL-induced stomatal closure and SHAM abolished NO production. YEL-elicited [Ca 2 + ] cyt oscillations were inhibited by SHAM but not by the atrbohD atrbohF mutation. These results indicate that YEL induces stomatal closure accompanied by ROS production mediated by peroxidases and NO production.
Abstract: Salicylic acid (SA), a ubiquitous phenolic phytohormone, is involved in many plant physiological processes including stomatal movement. We analysed SA-induced stomatal closure, production of reactive oxygen species (ROS) and nitric oxide (NO), cytosolic calcium ion ([Ca2+]cyt) oscillations and inward-rectifying potassium (K+in) channel activity in Arabidopsis. SA-induced stomatal closure was inhibited by pre-treatment with catalase (CAT) and superoxide dismutase (SOD), suggesting the involvement of extracellular
ROS. A peroxidase inhibitor, SHAM (salicylhydroxamic acid) completely abolished SA-induced stomatal closure whereas neither an inhibitor of NADPH oxidase (DPI) nor atrbohD atrbohF mutation impairs SA-induced stomatal closures. 3,3-Diaminobenzidine (DAB) and nitroblue tetrazolium (NBT) stainings demonstrated that SA induced H2O2 and O2– production. Guard cell ROS accumulation
was significantly increased by SA, but that ROS was suppressed by exogenous CAT, SOD and SHAM. NO scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline- 1-oxyl-3-oxide (cPTIO) suppressed the SA-induced stomatal closure but did not suppress guard cell ROS accumulation whereas SHAM suppressed SA-induced NO production. SA failed to induce [Ca2+]cyt oscillations in guard cells whereas K+in channel activity was suppressed by SA. These results indicate that SA induces stomatal closure accompanied with extracellular ROS production mediated by SHAM-sensitive peroxidase, intracellular ROS accumulation
and K+in channel inactivation.
Abstract: Growing on test was conducted in aluminum trays and photographic cassette holders to determine the germination and seed transmission of jute leaf mosaic agent using five Corchorus capsularis cultivars. The test cultivars (D-154 and CVL-1) were grown in successive two years in a net house. Seeds collected from early-infected plants were used in the second year. Significantly higher percentage of seed transmission was obtained in the second year. Among the five test cultivars grown in two agro- ecological zones CVL-1 performed the best but none of the cultivars was free from leaf mosaic disease infection. Agro-ecological factors influenced the occurrence of the disease
Abstract: Fifteen advanced lines of tomato including two check cvs. `Manik` and `BARI-10` were assessed under natural epiphytotics for their performance to late blight (Phytophthora infestans) and early blight (Alternaria solani). The highest late blight disease incidence was found in V-52 & V-215 and the lowest in V-378. Two lines were found resistant (V-426 & V-259), two moderately resistant (V-187 & V-385), two were tolerant (V-282 & V-422), four moderately susceptible (V-378, V-138, V-258 and BARI 10), three were susceptible (V-330, V-201 and Manik) and two highly susceptible (V-52 & V-215), but none was found highly resistant. In case of early blight V-259 showed the highest and V-215 showed the lowest disease incidence. On the basis of early blight disease intensity, one was found resistant (V-52), three were moderately resistant (V-138, V-201 and V-215), six were moderately susceptible (V-378, V-282, V-330, V-426, V-422 and Manik), four were susceptible (V-187, V-385, V-258 and BARI 10), one was highly susceptible (V-259) and none was found highly resistant.
Abstract: Eight cultivars of tomato were studied under field condition in insecticide treated and non treated plots to observe the performance of these varieties against leaf curl disease. The effect of this disease in percent plant infection, insect population per plant, percent leaf area diseased, number of fruits per plant, weight of individual fruit (g), yield per plant (kg) and yield loss due to leaf curl infection were investigated. None of the varieties was found to be resistant against viral leaf curl disease. But the cultivar Raton was found to be somewhat resistant both in controlled and treated plots. In controlled plots the second best performance was shown by Manik. The other varieties were more or less affected by leaf curl virus. In insecticide treated plots, second highest yield was observed in Manik and Roma-VF varieties indicating that the cultivar Roma-VF has the potential to perform as good as Manik when cultivated under insecticidal condition. The cultivar Anobic suffered more due to leaf curl viral disease in terms of yield parameters under both insecticide treated and non-treated plots. Vector management using Malathion, improved the growth and yield parameters of cultivars.
