Development Of Blight Research Articles

Temporal and spatial dynamics of ascochyta blight caused by Ascochyta fabae speg. In faba bean fields in Tunisia

Ascochyta blight of faba bean, caused by Ascochyta fabae (teleomorph: Didymella fabae) is one of the most destructive diseases of faba bean in Tunisia. Temporal and spatial development of ascochyta blight were studied and characterized during 2010–2011 and 2011–2012 in three faba bean fields located in Oued Mliz, Oued Beja and Mornag, using mathematical and geostatistical analyses. Mass Disease Index (MDI) was assessed every two weeks in each quadrat located around the central source of inoculum. Richards’ function well described disease progress in all sites except for Oued Beja in 2011–2012, the shape parameter m is significantly close to 1 placing the model in its particular form of Gompertz and confirming the polycyclic characteristic of the epidemic. Empirical analysis showed that the effect to locations on epidemic dynamics was explained by highly significant environmental effect (temperature, rain events). These differences in epidemic dynamics were confirmed by the analysis of parameters estimated by the Richards’ model (average relative disease progression rate (rw), proportional average relative disease progression rate (rwp), maximum disease progression rate at inflection point (ri), time at inflection point (ti), MDI at the inflection point (yi)). Analyzing the spatial structure dynamics of the disease using Lloyed Index of Patchiness (LIP) and the mapped disease distribution at different dates showed that LIP was estimated by an exponential functionthat decreased over time in all sites and seasons. LIP dropped below 1 (limit value for aggregated distribution) after 12, 25, 30, 36 and 48 daysat Oued Beja and Oued Mliz during both seasons and during the second season in Mornag. After these periods, the disease distribution is randomly distributed. However, according to the mapping, disease distribution was aggregated in terms of severity even at the end of the epidemics, indicating different temporal dynamics such as changes in distance from the inoculum source.

Selected climatic variables in Slovakia are favourable to the development of Dothistroma needle blight

Abstract Dothistroma needle blight (DNB) is a disease of pine needles. It causes significant defoliation of affected trees; intensive attacks lead to damages of the whole stand. The relationship of trends in disease severity and intensity with climatic variables were studied in three Austrian pine plantations (Jahodná, Kálnica, Litava) during 2014–2018. During the monitoring period, the greatest variability in disease severity was observed in the top third of the crowns, which showed the highest correlation with the variants of the most important climatic conditions (temperature and relative humidity) tested. For the spread of DNB, based on statistical assessment, a higher number of intervals of environmentally favourable climatic conditions is crucial. Both Dothistroma species (D. septosporum and D. pini), which are causal agents of the disease, were identified in Jahodná. In Kálnica and Litava, only D. septosporum was present.

Sheath blight development and yield loss on rice in different epidemiological conditions

Rice sheath blight and its causal agent Rhizoctonia solani AG-1 IA are associated with intensive and high input production systems. To our knowledge, resistant varieties have not been introduced for this disease, thus good crop management is expected to be among viable disease control methods. The aims of the present study were to determine the effect of different rates of nitrogen fertilizer, planting spaces and inoculum densities on sheath blight incidence and severity, including grain yield loss. Additionally we aimed to identify those developmental stages that are more susceptible to the disease. Field experiments were conducted over two consecutive years, in 2017 and 2018 in the Guilan province of Iran. Results indicated that higher N rates, denser planting and higher initial inoculum density resulted in greater disease development. Among five different growth stages, inoculation of plants at booting and flowering stages, resulted in maximum disease severity and grain yield loss. Taken together, reasonable use of nitrogen fertilizer, optimum planting space and reduced inoculum density obtained by spraying fungicide at the booting and flowering stages of rice are suggested as the best options to control sheath blight epidemics in rice.

Effect of Chemical Inducers of Systemic Acquired Resistance (SAR) for the Management of Late Blight Disease of Potato

Late blight of potato is one of the most devastating diseases with great economic importance. Among several disease management strategies, ISR (Induced systemic resistance) plays an important role in checking the disease spread. So, in the present study, nine different SAR chemical inducers viz. Phosphoric acid, Salicylic acid, Naphthalene acetic acid(NAA), Benzoic acid, Benzothiadiazole, Dichloro-iso nicotinic acid (INA) and Kinetin were evaluated at 0.05% (C1), 0.10% (C2) and 0.15% (C3) concentrations, whereas Calcium chloride and Ascorbic Acid at 3.5% (C1), 5.0% (C2), 6.5% (C3) and 1.5% (C1), 2.0% (C2), 2.5% (C3) respectively at three different concentrations each, along with positive and negative checks of standard fungicide metalaxyl 8+ macozeb 64 WP @0.25% and control(water) respectively by spraying them at 2-3 compound leaf stage of plants which were challenged by P. infestans inoculations five days later in pots to assess disease incidence and intensity which were recorded at weekly intervals of four stages (stage I-IV). It was found that the foliar spray with benzothiadiazole (BTH) @ 0.10 to 0.15% was best in delaying the appearance of first symptoms of the disease by 11 days followed by salicylic acid@ 0.10 to 0.15% and ascorbic acid @ 2.5% which delayed the symptom appearance by 9 days, whereas the standard fungicidal spray of metalaxyl 8 + mancozeb 64 WP at the recommended concentration of 0.25% delayed the symptom appearance by only 8 days when compared to water sprayed check. It was also found that on an average, BTH sprays completely arrested the late blight development (0% intensity) followed by salicylic acid, INA and ascorbic acid sprays exhibiting 0.46-0.74% mean blight intensity compared to 2.00 and 6.28 percent intensity recorded, respectively, on metalaxyl 8 + mancozeb 64 WP and water-sprayed plants one week after first appearance of disease in control pots (stage I). These treatments with chemical inducers showed an increase in the activity of peroxidases and polyphenol oxidases in the infected potato leaves as a result of SAR activity at all stages (stage I-IV). Average maximum peroxidase activity of 19.01-20.66 mg and polyphenol oxidase activity of 2.70-2.89 mg were recorded in the potato leaves during stage-I, sprayed with either BTH, benzoic acid, phosphoric acid or salicylic acid as compared to only (16.78 mg and 2.28 mg), (4.66 mg and 1.36 mg) recorded in (metalaxyl 8 + mancozeb 64 WP) and water-sprayed check respectively. The highest concentrations of all the test chemicals, in general, showed increased biochemical activity thereby yielding lesser blight intensity compared to their lower concentrations.

Timing of Susceptibility to Fusarium Head Blight in Winter Wheat.

The duration of wheat susceptibility to Fusarium infection has implications for risk forecasting, fungicide timing, and the likelihood that visible kernel damage may underpredict deoxynivalenol (DON) contamination. A field experiment was conducted to explore the impact of varying infection timings on Fusarium head blight (FHB) development in winter wheat. Trials in four successive years (2010 to 2013) in North Carolina utilized one susceptible and one moderately resistant cultivar possessing similar maturity, stature, and grain quality. Inoculum was applied in the form of sprayed Fusarium graminearum conidia. In the first year, the nine infection timings were from 0 to 21 days after anthesis (daa), whereas in the following 3 years, they ranged from 0 to 13 daa. Infection progression was compared among inoculation timings by sampling spikes five to six times during grain-fill. Based on DON, percent kernel damage and kernel infection, and fungal spread as assayed via qPCR, the moderately resistant cultivar had at least a 2- to 3-day shorter window of susceptibility to damaging FHB infection than the susceptible cultivar. The results suggest that duration of susceptibility is an important aspect of cultivar resistance to FHB. In 2012, the window of susceptibility for both cultivars was extended by cold snaps during anthesis. After debranning in one year, the majority of DON was found to be in the bran fraction of kernels; there was also a trend for later infections to lead to a higher percentage of DON in the nonbran fraction, as well as a higher ratio of DON to FDK.

Xanthomonas axonopodis pv. punicae depends on multiple non-TAL (Xop) T3SS effectors for its coveted growth inside the pomegranate plant through repressing the immune responses during bacterial blight development

Xanthomonas axonopodis pv. punicae (Xap), the bacterial blight pathogen of pomegranate, incurs substantial loss to yield and reduces export quality of this economically important fruit crop. During infection, the bacterium secretes six non-TAL (Xop) effectors into the pomegranate cells through a specialized type three secretion system (T3SS). Previously, we demonstrated the role of two key effectors, XopL and XopN in pathogenesis. Here, we investigate the role of rest effectors (XopC2, XopE1, XopQ and XopZ) on disease development. We generated null mutants for each individual effector and mutant bacterial suspension was infiltrated into pomegranate leaves. Compared to Xap wild, the mutant bacterial growth was reduced by 2.7–11.5 folds. The mutants produced lesser water-soaked lesions when infiltrated on leaves by 1.13–2.21 folds. Among the four effectors, XopC2 contributes highest for in planta bacterial growth and disease development. XopC2 efficiently suppressed the defense responses like callose deposition, reactive oxygen species (ROS) and the activation of immune responsive genes. Being a major contributor, we further characterize XopC2 for its subcellular localization, its protein structure and networking. XopC2 is localized to the plasma membrane of Nicotiana benthamiana like XopL and XopN. XopC2 is a 661 amino acids protein having 15 alpha and 17 beta helix. Our STRING and I-TASSER based analysis hinted that XopC2 interacts with multiple membrane localized plant proteins including transcription regulator of CCR4-NOT family, TTN of maintenance of chromosome family and serine/threonine-protein phosphatase 2A (PP2A) isoform. Based on the interaction it is predicted that XopC2 might involve in diverse functions like nuclear-transcribed mRNA catabolic process, maintenance of chromosome, hormone signaling and protein dephosphorylation activities and thereby suppress the plant immunity. Altogether, our study suggests that Xap largely depends on three non-TAL (Xop) effectors, including XopC2, XopL and XopN, to modulate pomegranate PTI for its unrestricted proliferation during bacterial blight development.

ВРОЖАЙНІСТЬ КУКУРУДЗИ ЗАЛЕЖНО ВІД СТРОКІВ ТА КРАТНОСТІ ЗАСТОСУВАННЯ ФУНГІЦИДІВ В УМОВАХ ЗАХІДНОГО ЛІСОСТЕПУ УКРАЇНИ

Досліджено сучасний стан виробництва кукурудзи в Україні та світі, її значення, як однієї з головних експортних культур. Показано вплив застосування фунгіцидів на розвиток основних хвороб кукурудзи по таких фазах розвитку: 12 листків, фаза цвітіння, фаза воскової стиглості зерна. Чотириразове внесення фунгіцидів дозволило зменшити відсоток рослин уражених плямистостями на 15,2-15,3% відносно контролю у фазі воскової стиглості зерна. Відсоток рослин уражених іржею склав 20,2 у варіанті з триразовою обробкою препаратами. Чотириразове застосування фунгіцидів дозволило зупинити розвиток фузаріозу качана на рівні 12,9 %, проти 26,3% на контрольному варіанті. Починаючи з дворазового обприскування препаратами відсоток уражених рослин складав не більше 21,5%. Наведено дані про вплив застосування фунгіцидів на врожайність кукурудзи залежно від терміну та кратності обробок рослин. Визначено, що кратність обробок фунгіцидами у різні фази розвитку рослин має вплив на формування врожаю кукурудзи. Зі збільшенням кратності обприскувань отримували вищий врожай. Одноразове застосування фунгіцидів дозволило отримати на 0,5-1,04 т/га зерна більше відносно контролю, дворазове – 1,35-2,04 т/га. Найвищий приріст врожайності +3,4 т/га забезпечив варіант з чотириразовим внесенням фунгіцидів у фазах 10 листків + викидання волоті + після цвітіння + налив зерна. У варіанті з трьохразовою обробкою (викидання волоті + після цвітіння + налив зерна) отримали +3,13 та +2,69 т/га до контролю залежно від термінів застосування. Варіанти з пізнішими термінами внесення фунгіцидів забезпечували вищий приріст врожаю зерна кукурудзи порівняно із ранніми термінами (10 листків). Досліджено, що вміст мікотоксинів (фумонізин В1, Т-2 токсин, зеараленон та дезоксиніваленол - ДОН) у зерні кукурудзи не перевищує граничні межі у жодному з варіантів та знижується зі збільшенням кратності обробок фунгіцидами.

Desarrollo de la mancha foliar por Bipolaris maydis (teleomorfo: Cochliobolus heterostrophus) en maíz dulce, en función de nitrógeno, potasio y silicio en invernadero

El objetivo del trabajo fue evaluar el desarrollo de la mancha foliar causada por Bipolaris maydis, enfermedad común e n maíz dulce, según la dosis y el acumulado de nitrógeno, potasio y silicio, en condiciones de invernadero. Los tratamientos consistieron en cinco dosis de nitrógeno (N) (0, 200, 400, 800 y 1.200 kg/ha), aplicación o no de potasio (K) (240 kg/ha) y aplicación o no de silicio (Si) (380 kg/ha). Se empleó un diseño experimental completamente aleatorizado con esquema factorial 5 x 2 x 2 y tres repeticiones. Se inocularon todos los tratamientos a los 30 días con una suspensión de 2 x 105 conidios por mL de B. maydis. A los 42 días se midió la acumulación de N, K y Si, así como el porcentaje de infección y el área bajo la curva de progreso de la enfermedad (ABCPE). Los tratamientos que recibieron fertilización con Si y K presentaron mayores acumulados de N, K y Si, y niveles más bajos de intensidad de ataque y ABCPE. Los acumulados de N, K y Si presentaron variaciones frente a las interacciones de la fertilización de K con N, y de Si con N; sin embargo, los niveles de las variables de la enfermedad fueron menores en la fertilización con K o Si, combinadas con las dosis de 0, 200 y 400 kg/ha de N.

BLIGHT – A LITTLE-KNOWN DISEASE OF SOY IN KAZAKHSTAN

For the first time, the causative agent of late blight Phytophthora megasperma Drech. in Kazakhstan found on soybean crops in 2015. It is a quarantine disease. The article provides data on the spread of the disease, describes the symptoms of late blight soy. The frequency of the development of the disease depending on weather conditions has been established, the parasitic kind of the pathogen in Kazakhstan has been identified and biological features have been studied. The source of infection of the disease are plant debris, soil and seeds. All biotic and abiotic factors that weaken plants predispose them to infection. For sowing, only healthy seed material should be used, since the causative agent of late blight hibernates in infected seeds. Timely implementation of agricultural practices during the growing season contributes to the good development of plants, thereby increasing their resistance to the disease. Reduced degree of late blight also with a rarer plant standing. So, in the experiments, when sowing of rows between rows of 60 cm of soybean lesions by late blight was performed, it decreased by 7.7%. Chemical measures for the control of late blight have been developed. Studies on the use of contact and systemic fungicides against late blight soy show that all using drugs inhibit the development of late blight. The most effective fungicides were ridomil and metalaxyl, where their biological effectiveness was 30.7-47.3%. The zoned and promising varieties and hybrids of local and foreign soybean breeding are evaluated for disease resistance. Varieties and hybrids immune to the disease have not been identified. Resistant to late blight French varieties Dicabit.

Effect of Increased Silicon Content of Paddy Rice on Sheath Blight Development through Carbonized Rice Husk Application

Effect of Increased Silicon Content of Paddy Rice on Sheath Blight Development through Carbonized Rice Husk Application

Screening, identification and antagonistic effect evaluation of biocontrol strains to Asarum leaf blight

Leaf blight is the main disease of Asarum. At present, chemical treatment is main measure for disease control, and there is no report on biological control. In order to achieve the biological control of Asarum leaf blight, the biocontrol strains with antagonistic effect on Asarum leaf blight were screened. The rhizosphere bacteria of healthy Asarum plants were isolated by soil dilution method, and the isolated strains were screened by the methods of antagonistic antifungal and fermentation liquid antifungal, then the strains were identified and the control effect in vivo was determined. Abiocontrol bacterial strains S2-31 which with high antagonism to leaf blight was obtained from more than 100 isolated strains. The inhibitory rates of antagonistic antifungal and fermentation liquid antifungal reached 92.47% and 60.56%, respectively. It was identified by morphology and 16 S rDNA sequence analysis, and the strain was identified as Brevibacillus laterosporus. The results of indoor potted experiment showed that the control effect was 79.87%, 71.44% and 66.82% on the 3 rd, 5 th and 7 th day after inoculation, respectively, which indicated that S2-31 could reduce the disease index and control the development of Asarum leaf blight.

The Effectiveness of Endophytic Fungi Origin of Potato Plant Roots in Coffee Skin Compost Media to Suppress Development of Potato Leaf Disease (Phytophtora infestans)

Potato leaf blight is caused by Phytophthora infestans fungus is one of the important diseases in potato plants. The decrease in potato production due to P. infestans can reach 90%. Until now, P. infestans pathogen attack is an important problem and there is no fungicide that is really effective against the disease. This study aims to examine the effectiveness of endophytic fungi from potato roots in suppressing the development of P. infestans potato leaf blight disease carried out at University Farm Stasiun Riset Bener Meriah (UFBM) Syiah Kuala University Tunyang Village, Timang Gajah District, Bener Meriah Regency from May to October 2014. The method used is the experimental method. The results of this study indicate that endophytic fungi from the roots of potato plants in coffee skin compost media can suppress the development of leaf blight caused by P. infestans, endophytic fungi from potato plant roots in coffee skin compost media. The best results were found in B9 endophytic fungi isolates with the intensity of the pathogen attack P. infestans 48.00%, the intensity of damage to potato plants due to pathogen P. infestans and 2.60%, the weight of healthy tubers 332.4 grams.

Impact of predisposing factors on development of stemphylium blight of garlic under Punjab conditions

Effect of predisposing factors like leaf wetness duration, plant age, date of sowing, temperature, relative humidity, total rainfall and number of rainy days was studied on the severity of the Stemphylium blight of garlic (Stemphylium vesicarium). With an increase in the leaf wetness duration and age of plant, corresponding decrease in the incubation period and increase in the rate of disease progress was recorded. Minimum 8 hours of leaf wetness duration is required for the initiation of the disease under controlled conditions. Highest disease severity was found at 25ºC (63.11 per cent) followed by 30ºC (56.00 per cent) and 20ºC (49.78 per cent) and the disease progress ceased altogether at 15ºC. The rate of disease severity was less in the late sown crop (16th Nov) in comparison to early sown crop (10th oct, 26th Oct). Rainfall coupled with dry and warm weather was optimum for the growth of the pathogen which resulted in increased disease severity. Maximum and minimum temperature, maximum and minimum relative humidity, total rainfall and number of rainy days were positively correlated with the disease severity.

Effect of climatic variability and weather factors on development of tomato early blight in a hot semi-arid region of Southern India

Effect of climatic variability and weather factors on development of tomato early blight in a hot semi-arid region of Southern India

SPATIAL DISTRIBUTION OF EARLY BLIGHT DISEASE ON TOMATO, CLIMATIC FACTORS AND BIOEFFICACY OF PLANT EXTRACTS AGAINST Alternaria solani

Information on the spatial variability in plant disease is essential for location-based disease management. In the current study, the spatial distribution of tomato early blight disease was ascertained in District Gilgit, GilgitBaltistan, Pakistan. The comprehensive field survey was carried in two growing seasons (2014–2015), whereas in each growing season, 62 tomato fields were surveyed. Based on the distribution of disease, the respective thematic maps (incidence and severity) were prepared using Arc Map 10.1 with spatial analyst function of Arc GIS software by means of the inverse distance weight (IDW) interpolation method. Results indicate that early blight of tomato is spatially distributed in both growing seasons. However, in the first growing season, the disease incidence ranged from 10.22% to 44.16% and during later season 14.03–49.16%, whereas 5.37–16.40% and 6.52–26.94% severity was recorded. Furthermore, this information indicates that higher disease infestation occurred in 2015 in relation to 2014. This information linked to metrological data (temperature, precipitation and relative humidity), seemingly favored the early blight development during the growing period. Seven botanical extracts were tested against pathogen Alternaria solani at different concentrations (4, 6 and 8%). Results revealed that all tested plant extracts showed antifungal activities. However, at 8% concentration of plant extract, Datura starmonium, Berberis orthobotry, Podophyllum emodi and Uretica dioica exhibited >60%, while Peganum harmala, Artemisia maritima and Capparis spinosa <60% antifungal properties. The information generated due to this study could help the tomato growers regarding disease management and selection of resistant cultivars, improving profitability and food security in the Gilgit region.

Relationship between onion thrips (Thrips tabaci) and Stemphylium vesicarium in the development of Stemphylium leaf blight in onion

AbstractStemphylium leaf blight caused by Stemphylium vesicarium and onion thrips (Thrips tabaci) are two common causes of leaf damage in onion production. Onion thrips is known to interact synergistically with pathogens to exacerbate plant disease. However, the potential relationship between onion thrips and Stemphylium leaf blight is unknown. In a series of controlled laboratory and field trials, the relationship between thrips feeding and movement on the development and severity of Stemphylium leaf blight were examined. In laboratory assays, onions (“Avalon” and “Ailsa Craig”) with varying levels of thrips feeding damage were inoculated with S. vesicarium. Pathogen colonisation and leaf dieback were measured after 2 weeks. In pathogen transfer assays, thrips were exposed to S. vesicarium conidia, transferred to onion and leaf disease development was monitored. In field trials, insecticide use was examined as a potential indirect means to reduce Stemphylium leaf blight disease and pathogen colonisation by reducing thrips damage. Results from laboratory trials revealed that a reduction in thrips feeding decreased S. vesicarium colonisation of onion leaves by 2.3–2.9 times, and decreased leaf dieback by 40–50%. Additionally, onion thrips were capable of transferring S. vesicarium conidia to onion plants (albeit at a low frequency of 2–14% of plants inoculated). In field trials, the symptoms and colonisation of Stemphylium leaf blight were reduced by 27 and 17%, respectively with the use of insecticide to control thrips. These results suggest that onion thrips may play a significant role in the development of Stemphylium leaf blight, and thrips control may reduce disease in commercial onion fields.

Future development of apricot blossom blight under climate change in Southern France

Climate change will have several consequences for agro-systems, one of which will concern changes to the development of pathogens. Because of the losses it causes, particularly in organic farming, Monilinia laxa is an important pathogen affecting apricot crops. This study focuses on the consequences of climate change regarding blossom and twig blight (Monilinia laxa) of apricot. To achieve this, a Climatic Index of cumulated Blight risk (CIB) was built, to obtain the weighted sum of blossom blight incidence throughout the blooming period. An epidemiological model to calculate the incidence of blossom blight during every potentially infectious episode and based on biological parameters, was calibrated using a trap pot experiment where trees were placed in orchards and subject to various meteorological conditions. The CIB derived from this model was evaluated on field data, and was shown to be a robust and useful tool to predict the effects of climate change on the development of apricot blight. Then, using the CIB with a phenological model to predict blooming periods in the future, we estimated the risks of apricot blight until 2100 on four contrasted apricot cultivars and in three geographical zones under climate change scenarios RCP 4.5 and 8.5. This study revealed different effects of climate change depending on the cultivar and altitude. Apricot trees would bloom earlier (up to a difference of 50 days between 1950 and 2100) under climate change. Under the combined effects of these shifts of blooming period and changing climatic conditions, late cultivars such as Bergarouge might see a reduction in the risk of blossom blight (down to 31%) because of warmer but dryer blooming periods. Other varieties (e.g.: Bergeron) could experience an increase in this risk by up to 27% with a shift of the blooming period towards rainier conditions at the highest altitudes. The results of this study could be used to anticipate future changes as well as be used at present as a decision-support tool for farmers.

Does winter oilseed rape as a winter cover crop influence potato late blight development in an organic crop rotation?

ABSTRACTIn this study, the effects of a winter cover crop (CC) and its combination with composted cattle manure (CC-M) on the development of potato late blight (Phytophthora infestans) and crop yield were investigated and compared with a system with no cover crop (NC). In the CC and CC-M systems, winter oilseed rape (Brassica napus L) was used as the winter cover crop before potatoes. The hypothesis that the cover crop could be used as a possible control strategy against late blight in organic potato cultivation was not confirmed. Although the progression of foliar late blight damage in CC treatment was significantly slower in the early stages of disease development relative to NC, CC did not significantly reduce late blight at the later stages, or over the full season, and it did not increase tuber yield. Adding cattle manure to the CC treatment favoured late blight development and the damage was significantly more severe than in the other systems and tuber yield was nominally lower (though not significantly). The late blight pressure differed between treatments, with early disease development significantly slower on CC plots compared to CC-M in both growing seasons, but still not different to that in the plants grown in the NC system. Based on the results, in regions where oospores are a primary infection source, making P. infestans a soilborne pathogen, the use of cover crops may provide a sustainable strategy for reducing late blight damage in an organic system, but further investigation is needed.

Biological control of rice sheath blight disease with formulation of indigenous Trichoderma strains under paddy field conditions

The effectiveness of indigenous Trichoderma strains in preventing sheath blight disease was evaluated during two growing seasons under paddy field conditions. Broom sorghum seeds were used for mass production of Trichoderma strains. Colonized seeds were ground to powder and mixed with talc and carboxymethyl cellulose. Suspensions were made from the bioformulations and sprayed onto rice plants. Effects of Trichoderma strains on disease incidence and severity as well as yield and other growth parameters were determined and compared with a chemical fungicide and a commercial biofungicide. A combined analysis of variance across two years was performed and a statistically significant effect of year, treatment and their interaction was reported. Results indicate that environmental factors and different biological fungicides had a strong effect on disease development under natural conditions. According to the results, propiconazole and T. harzianum AS12-2 resulted in the least disease severity and incidence. Overall, the efficacy of T. harzianum AS12-2 in reducing sheath blight development was significantly better than other Trichoderma treatments and was comparable to the conventional fungicide.

XopR T3SS-effector of Xanthomonas oryzae pv. oryzae suppresses cell death-mediated plant defense response during bacterial blight development in rice.

Xanthomonas oryzae pv. oryzae (Xoo) causes bacterial blight disease that limits the rice production globally. The bacterium secretes effector proteins directly into plant cells through a type III secretion system (T3SS). Here, we examined the role of a conserved XopR T3SS-effector in the suppression of host basal defense response. Phylogenetic and sequence analysis showed that XopR is well conserved within Xoo strains but shares varying degree of similarity among the other Xanthomonas species. The expression of XopR was shown to be regulated by hrpX, a key regulator of hrp cluster. For functional analysis we employed two mutant strains of Xoo, one lacks xopR gene and other lacks hrpX gene (making the strain defective in T3SS). Programmed cell death (PCD) events was examined both in rice and tobacco leaves through trypan blue staining method. In XopR expressing tobacco leaves the PCD induction was compromised. We observed higher PCD on rice leaves inoculated with Xoo mutants lacking either xopR or functional T3SS as compared to wild type. Contrary, when xopR gene was complemented in mutated strain the PCD was suppressed which clearly suggests that XopR acts as suppressor of the PCD mediated defense response. The EYFP::XopR fusion protein was shown to be localized to the plasma membrane of Nicotiana benthamiana and onion epidermal cells. Altogether our study leads to the understanding that XopR T3SS-effector is essential for Xoo to suppress PCD, primarily to support the in planta colonization of Xoo during blight pathogenesis.