Severity Of Bacterial Leaf Blight Research Articles

Microbial consortium formulation in liquid organic fertilizer for managing bacterial leaf blight (Xanthomonas oryzae pv. oryzae), rice blast (Pyricularia oryzae), and enhancing rice productivity

Abstract. Nurcahyanti SD, Masnilah R, Budiman SA, Tanzil AI, Nurdika AAH. 2024. Microbial consortium formulation in liquid organic fertilizer for managing bacterial leaf blight (Xanthomonas oryzae pv. oryzae), rice blast (Pyricularia oryzae), and enhancing rice productivity. Biodiversitas 25: 2208-2220. The productivity of rice is significantly influenced by soil fertility and plant diseases as limiting factors. The overreliance on synthetic fertilizers and pesticides in rice cultivation has led to declining land quality. We propose the utilization of Liquid Organic Fertilizers (LOF) enriched with beneficial microbes as a sustainable solution to maintain soil fertility and protect plants from pathogens. Our research specifically focuses on the formulation of LOF enriched with the microbial consortium to enhance rice productivity and suppress bacterial leaf blight (Xanthomonas oryzae pv. oryzae), and rice blast (Pyricularia oryzae) diseases. The three LOF treatments were formulated from vegetable and fruit waste (FV), Rice Straw (RS), and Cattle Manure (CM) with a microbial consortium consisting of Pseudomonas putida Pf10, Bacillus subtilis JB12, and Trichoderma sp. The results showed that the LOF from the three materials is suitable for the growth of the microbial consortium with a population of 104-109 CFU/mL, has macro-micronutrient content, pH at 6.5-6.8, and C-organic to support plant growth. The applications of the three types of LOF were able to suppress the severity of bacterial leaf blight by up to 21% and rice blast by 4% at eight weeks after inoculation. All LOF treatments are capable of enhancing the growth and production of rice. There were no significant differences in LOF materials for disease suppression, growth, and rice production.

Effect of Application of Endophytic Bacteria on the Development of Bacterial Leaf Blight Disease, Growth, and Production of Rice Plants

Bacterial leaf blight can be found in various stages of rice plant growth, so this disease can affect the growth and production of rice plants. This research aims to determine the effect of applying an endophytic bacterial formula to rice seedlings on the development of HDB disease, growth, and production of rice plants. This study used 4 isolates of endophytic bacteria (isolates BE-KH1, BE-M2, BE-M3, and BE-S5) which were formulated in coconut water waste + peptone. The results of the study showed that the application of the endophytic bacterial formula to rice seedlings was able to reduce the severity of bacterial leaf blight by 54,5 – 63,2% and had an effect on growth, full grain weight, and rice grain weight in rice plants inoculated with Xanthomonas oryzae pv. oryzae bacteria.

Strategy For Controlling Bacterial Leaf Blight (Xanthomonas sp.) on Eucalyptus Pellita Plants by Administering P. aeruginosa RE081

The demand for Eucalyptus Pellita seeds as a high-throughput inoculum (HTI) crop commodity in the field is extremely high. However, Xanthomonas sp., a bacteria that causes bacterial leaf blight, poses a significant challenge in ensuring a steady supply of healthy seedlings in nurseries. Researchers have explored using the rhizobacteria P. aeruginosa RE081 as an environmentally friendly biocontrol agent to address this issue. This study aims to determine the optimal concentration of P. aeruginosa RE081 that can effectively reduce the incidence and severity of bacterial leaf blight caused by Xanthomonas sp. The research was conducted using a completely randomized design, with different concentrations of P. aeruginosa RE081 (105, 106, 107, 108 CFU/mL) being tested. The findings indicate that the biological agent's concentration significantly impacts plant disease occurrence and severity. In vivo testing revealed that P. aeruginosa RE081 reduced disease severity by only 2.13% at a 108 CFU/mL concentration. Interestingly, concentrations lower than 108 CFU/mL increased disease severity compared to the control group.

Bio-functionalized nickel-silica nanoparticles suppress bacterial leaf blight disease in rice (Oryza sativa L.).

Bacterial leaf blight (BLB) caused by Xanthomonas oryzae pv. oryzae (Xoo) is one of the most devastative diseases that threatens rice plants worldwide. Biosynthesized nanoparticle (NP) composite compounds have attracted attention as environmentally safe materials that possess antibacterial activity that could be used in managing plant diseases. During this study, a nanocomposite of two important elements, nickel and silicon, was biosynthesized using extraction of saffron stigmas (Crocus sativus L.). Characterization of obtained nickel-silicon dioxide (Ni-SiO2) nanocomposite was investigated using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Transmission/Scanning electron microscopy (TEM/SEM), and energy-dispersive spectrum (EDS). Antibacterial activities of the biosynthesized Ni-SiO2 nanocomposite against Xoo were tested by measuring bacterial growth, biofilm formation, and dead Xoo cells. The bacterial growth (OD600) and biofilm formation (OD570) of Xoo treated with distilled water (control) was found to be 1.21 and 1.11, respectively. Treatment with Ni-SiO2 NPs composite, respectively, reduced the growth and biofilm formation by 89.07% and 80.40% at 200 μg/ml. The impact of obtained Ni-SiO2 nanocomposite at a concentration of 200 μg/ml was assayed on infected rice plants. Treatment of rice seedlings with Ni-SiO2 NPs composite only had a plant height of 64.8cm while seedlings treated with distilled water reached a height of 45.20cm. Notably, Xoo-infected seedlings treated with Ni-SiO2 NPs composite had a plant height of 57.10cm. Furthermore, Ni-SiO2 NPs composite sprayed on inoculated seedlings had a decrease in disease leaf area from 43.83% in non-treated infected seedlings to 13.06% in treated seedlings. The FTIR spectra of biosynthesized Ni-SiO2 nanocomposite using saffron stigma extract showed different bands at 3,406, 1,643, 1,103, 600, and 470 cm-1. No impurities were found in the synthesized composite. Spherically shaped NPs were observed by using TEM and SEM. EDS revealed that Ni-SiO2 nanoparticles (NPs) have 13.26% Ni, 29.62% Si, and 57.11% O. Xoo treated with 200 µg/ml of Ni-SiO2 NPs composite drastically increased the apoptosis of bacterial cells to 99.61% in comparison with 2.23% recorded for the control. The application of Ni-SiO2 NPs significantly improved the vitality of rice plants and reduced the severity of BLB.

Seed treatments and seedling root soaking in biological agents improved plant growth and reduced bacterial leaf blight disease incidence in rice

Bacterial leaf blight (BLB) is caused by Xanthomonas oryzae pv. oryzae (Xoo), a seed-soil-air-borne pathogen that can reduce 60% of rice yield. The primary study intended to investigate the effect of seed treatments and root soaking with biological agents (a mixture of Pseudomonas diminuta and Bacillus subtilis) on plant growth and the severity of BLB in a greenhouse. A split-plot experimental design was used with seed treatments as the main plot: negative control, positive control (Xoo inoculated), bactericide (streptomycin sulfate 20%) 0.2%, biopriming with biological agents 108 CFU ml−1, matriconditioning plus bactericide 0.2%, biomatriconditioning with biological agents 108 CFU ml−1. The subplots were root soaking: untreated, bactericide 0.1%, 0.2%, 0.4%, 0.6%; biological agents 106 CFU ml−1, 108 CFU ml−1, and 1010 CFU ml−1. Biomatriconditioning reduced the BLB incidence three weeks after sowing from 10.6% to 1.7% and increased plant height four weeks after transplanting (WAT). Biomatriconditioning followed by root soaking in the biological agents or 0.4 % bactericide increased plant dry weight 3 WAT. Biomatriconditioning or root soaking in the biological agents (106 CFU ml−1) provided the most significant number of tillers 4 WAT.

Comparison of the Antagonistic Potential of the Entomopathogenic Bacterium Serratia nematodiphila GCSR38 with other Effective Microorganisms for the Control of Rice Bacterial Leaf Blight

The efficacy of antagonistic microorganisms and secondary metabolites of entomopathogenic bacteria was evaluated in vitro and in vivo against Xanthomonas oryzae pv. oryzae (Xoo), a causal agent of rice bacterial leaf blight. The effect of the culture filtrates of the microorganisms was tested against Xoo, using the agar well diffusion assay. Trichoderma sp. UB05/3 was the most effective against Xoo. However, the results were not statistically different from those of the entomopathogenic bacterium Serratia nematodiphila GCSR38 with a 22.97 mm and 19.15 mm zone of inhibition, respectively. The effect of the secondary metabolite crude extracts of antagonistic microorganisms (2,000 µg/ml) on Xoo inhibition was tested by the paper disc diffusion method. Only S. nematodiphila GCSR38 was able to control Xoo, with an inhibition zone of 17.60 mm. Minimum inhibitory concentration (MIC) was determined using a 96-well microtiter plate. The MIC of secondary metabolites crude extracts of S. nematodiphila GCSR38 was 1,000 µg/ml and the minimum bactericidal concentration (MBC) was 1,000 µg/ml. The efficacy of the secondary metabolite crude extract of S. nematodiphila GCSR38 against Xoo was tested using the detached leaf technique; the secondary metabolite crude extracts controlled the disease, with 24.45% and 15.56% disease severity when used before and after inoculation with Xoo, respectively. Inoculation with Xoo alone resulted in a disease severity of 44.45%. The secondary metabolite crude extracts of S. nematodiphila GCSR38 can reduce disease severity of bacterial leaf blight in rice by 28.89%, whereas zinc thiazole causes a disease severity of 22.22% and Xoo alone causes a disease severity of 66.67%.

Use of Bacillus firmus E65-Talc Based Formulation for The Management of Bacterial Leaf Blight Disease

It has long been known that bacterial leaf blight (BLB) caused by Xanthomonas oryzae pv. oryzae (Xoo), is major bacterial diseases which occured widespread in rice growing countries. This study was performed to determine effect of biological control using endophyte bacteria formulated in talc-based powder against Xoo in rice agroecosystem which grown under organic system of rice intensification (SRI) in Cianjur-West Java. Carriers formulation of talc-based powder was prepared to contain endophytic bacteria of Bacillus firmus (isolate E65) which was previously isolated from the rice field. BLB disease suppression was ranged 2.14% to 97.15%. among cultivars tested, with the average BLB severity among six cultivars was 9.79%. The cv. Inpari 10 (Moderate) showed the lowest disease severity compared with that of resistance cv. Sintanur, Mekongga and Code. This suggests that the biocontrol efficacy of formulation B. firmus E65-talc-based powder was not affected by cultivar susceptibility. The antagonistic bacteria formulation yields up to 9%. The highest yields for each respective treatment treated with talc based-bacterial formulation were obtained using cv. Inpari 10 and Cisantana. The scale-up of biocontrol products that prolongs biocontrol activity may challenged with shelf life of formulation. This study showed advantages of single cultures of bacterial antagonist used in a talc-based formulation is possible to suppress BLB disease and promotes rice yield under SRI field condition.

Influence of temperature and daily leaf wetness duration on the severity of bacterial leaf blight of garlic

ABSTRACT In the present study, climate control chamber conditions were adopted to investigate the influence of temperature (10, 15, 20, 25 and 30°C) and leaf wetness duration (6, 12, 24 and 48 hours) on the severity of bacterial leaf blight of garlic, caused by Pseudomonas marginalis pv. marginalis. The relative density of lesions was influenced by temperature and leaf wetness duration (P<0.05). The disease was more severe at 20°C. The obtained data underwent non-linear regression analysis. Generalized beta function was used to fit the data on severity and temperature, while a logistic function was chosen to represent the effect of leaf wetness duration on the severity of bacterial blight. The response surface resulting of the product of those two functions was expressed as ES = 0.019419 * (((x-5)0.5893) * ((35-x)0.5474)) * (0.51754/(1+23.59597* exp (-0.145695*y))), where: ES represents the estimated severity value (0.1); x, the temperature (ºC), and y, the daily leaf wetness duration (hours). This model shall be validated under field conditions to assess its use as a forecast system for bacterial leaf blight of garlic.

Identification of a Chitooligosaccharide Mechanism against Bacterial Leaf Blight on Rice by In Vitro and In Silico Studies.

This study focuses on a commercial plant elicitor based on chitooligosaccharides (BIG®), which aids in rice plant growth and disease resistance to bacterial leaf blight (BLB). When the pathogen (Xoo) vigorously attacks rice that has suffered yield losses, it can cause damage in up to 20% of the plant. Furthermore, Xoo is a seed-borne pathogen that can survive in rice seeds for an extended period. In this study, when rice seeds were soaked and sprayed with BIG®, there was a significant increase in shoot and root length, as well as plant biomass. Furthermore, BIG®-treated rice plants showed a significant reduction in BLB severity of more than 33%. Synchrotron radiation-based Fourier transform infrared (SR-FTIR) analysis was used to characterize BIG®’s mechanism in the chemical structure of rice leaves. The SR-FTIR results at 1650, 1735, and 1114 cm−1 indicated changes in biochemical components such as pectins, lignins, proteins, and celluloses. These findings demonstrated that commercial BIG® not only increased rice growth but also induced resistance to BLB. The drug’s target enzyme, Xoo 1075 from Xanthomonas oryzae (PDB ID: 5CY8), was analyzed for its interactions with polymer ingredients, specifically chitooligosaccharides, to gain molecular insights down to the atomic level. The results are intriguing, with a strong binding of the chitooligosaccharide polymer with the drug target, revealing 10 hydrogen bonds between the protein and polymer. Overall, the computational analysis supported the experimentally demonstrated strong binding of chitooligosaccharides to the drug target.

Control of bacterial leaf blight and rice blast with antagonist microbial in the agroecosystem of irrigated rice

Bacterial leaf blight (Xanthomonas oryzae) and rice blast (Pyricularia oryzae) cause yield losses in rice production. Antagonist microbial application through seed treatment and foliar spray during rice growing stage is suggested to prevent the disease which is more reliable to reduce the disease incidence than curing it. This research aimed to determine the severity of bacterial leaf blight and rice blast among varieties that treated with antagonist microbial complex in the agro ecosystem of irrigated rice. Research was conducted in Kalibawang sub district, Kulon Progo, Yogyakarta, October 2018 to January 2019. The experimental design was randomized block design with 7 treatments and 4 replications. The treatments were the application of antagonist microbial complex formula A (Azotobacter vinelandii, Azospirillum sp., Bacillus cereus, Bradyzhizobium sp., and Methylobacterium sp. >107 CFU/g) and formula B (Azotobacter chroococum, Azotobacter vinelandii, Azospirillum sp., Pseudomonas cepacia, Penicillium sp., and Acinetobacter sp. >107 CFU/g) to several rice varieties (Inpari 9, Inpari 33, and Ciherang). Results shows that formula B had the lowest severity of bacterial leaf blight (14.44%) and leaf blast (6.94%) at Ciherang while formula A had the lowest panicle blast (6.55%). The highest yield (10.62 t/ha) was obtained from Ciherang treated with formula B.

Validation of a diagrammatic scale for quantification of bacterial leaf blight (causal agent Pseudomonas avenae) in maize

Bacterial leaf blight occurs in almost the entire Brazilian territory and can cause significant economic damage. However, its effects can be curtailed with the following tools that aid in quantification for carrying out the best severity assessment that can be applied to the studies used in its control. The objective of this study was to develop and validate a diagrammatic scale to quantify the severity of bacterial leaf blight in maize caused by Pseudomonas avenae. Corn leaves were collected with different levels of disease severity, and the total leaf area as well as the injured area of the middle third of each leaf was measured. From this, the minimum and maximum limits of the disease and, subsequently, four intermediate levels were determined whilst taking into account the law of visual stimulus of Weber-Fechner. Levels 1.5%, 2.5%, 9%, 18%, 46%, and 70% were selected with validation performed by eight evaluators, four inexperienced and four experienced. These evaluators estimated the severity values, initially without the use of the proposed diagrammatic scale and in a second attempt with the use of the scale. We concluded that it was possible to improve the accuracy and precision of the evaluators when they used the scale as a tool to assess the severity of bacterial leaf blight on corn leaves.

Validation of a diagrammatic scale for quantification of bacterial leaf blight (causal agent Pseudomonas avenae) in maize

Bacterial leaf blight occurs in almost the entire Brazilian territory and can cause significant economic damage. However, its effects can be curtailed with the following tools that aid in quantification for carrying out the best severity assessment that can be applied to the studies used in its control. The objective of this study was to develop and validate a diagrammatic scale to quantify the severity of bacterial leaf blight in maize caused by Pseudomonas avenae. Corn leaves were collected with different levels of disease severity, and the total leaf area as well as the injured area of the middle third of each leaf was measured. From this, the minimum and maximum limits of the disease and, subsequently, four intermediate levels were determined whilst taking into account the law of visual stimulus of Weber-Fechner. Levels 1.5%, 2.5%, 9%, 18%, 46%, and 70% were selected with validation performed by eight evaluators, four inexperienced and four experienced. These evaluators estimated the severity values, initially without the use of the proposed diagrammatic scale and in a second attempt with the use of the scale. We concluded that it was possible to improve the accuracy and precision of the evaluators when they used the scale as a tool to assess the severity of bacterial leaf blight on corn leaves.

Detection of the antibacterial efficacy of Paenibacillus polymyxa against Xanthomonas oryzae pv. oryzae in rice seedlings, and the antimicrobial related genes

Paenibacillus polymyxa bacterium has been known as a biocontrol agent (BCA) for various plant diseases, and it promotes the growth of several treated plants. On the other hand, Xanthomonas oryzae pv. oryzae (Xoo) is an important bacterial pathogen that causes bacterial leaf blight (BLB) to rice plants, and cause high yield loss during the growing season. In this study, P. polymyxa SX3 inhibited the in vitro growth of Xoo by 80% and affected the biofilm formation. Also, the cell membrane of Xoo lost its permeability after treating it with culture filtrate of P. polymyxa at its MIC (40%). Transmission electron microscopic (TEM) observations showed an influence of the culture filtrate of P. polymyxa on the cell morphology of Xoo. Applying P. polymyxa decreased the severity of bacterial leaf blight on rice seedlings to 4.9%, compared to 42.5% of the control. Moreover, this strain also improved the growth parameters of the rice seedlings significantly by increasing the shoot length, root length, fresh and dry weight by 166.7%, 168.2%, 100%, and 255.6%; respectively, compared to the positive control (Xoo only). Three antimicrobial related genes; pmxB, pmxD, and Fusdel were detected in P. polymyxa SX3 using nine specific gene markers. The aims of the study were to investigate the impact of P. polymyxa SX3 on in vitro growth of Xoo, in vivo growth of the rice seedlings in the greenhouse, and to detect the presence of related antimicrobial genes.

PENGARUH Trichoderma sp. SEBAGAI AGEN PENINGKATAN KETAHANAN TANAMAN PADI TERHADAP PENYAKIT HAWAR DAUN

Rice is one commodity that have an important value for Indonesian people food. But the production of rice plant decreased by attacking of insect and bacterial. The bacterialleaf blight caused by Xanthomonas oryzaepv.oryzae. To avoid the bacterial leaf blight could used Trichoderma sp. suspension to induced resistant in rice plant. This research was conducted at the Laboratory of Plant Disease and Greenhouse of Lampung University. This study was conducted from June 2016 to August 2016.The experiment was conducted in a complete randomized design arranged with two factors, namely varieties of rice and kind isolate of Trichoderma sp.. The results of this study showed that the application of Trichoderma sp. reducing the severity of bacterial leaf blight diseaseand the kind isolate of Trichoderma sp. can increase the length rootand height of rice plant.

DETECTION OF GENES RESISTANT TO BACTERIAL LEAF BLIGHT IN RICE CULTIVARS FROM SITUBONDO AND JEMBER, INDONESIA

Detection of genes resistant to bacterial leaf blight in rice cultivars from Situbondo and Jember, Indonesia. Xanthomonas oryzae pv. oryzae (Xoo), causing bacterial leaf blight, is a destructive pathogen that significantly affects rice production. The use of resistant varieties is the most effective and economical strategy to reduce the impact of the disease. This study aimed to analyze the genetic basis of resistance to Xoo in rice. The incidence and severity of bacterial leaf blight were assessed in the field through a diagonal random sampling method. PCR was used to detect resistant genes in rice with eight Xa-specific primers. The presence of Xa genes and environmental conditions were statistically analyzed to determine whether the disease incidence and disease severity were related to average temperature and rain intensity. The means for disease incidence and severity at the generative stage were higher than those at the vegetative stage. The 12 rice cultivars were categorized into four groups based on the presence of Xa gene sequences; most cultivars had Xa10 and Xa13, and one cultivar had five Xa genes. Disease incidence and severity were weakly correlated to the presence of resistance genes, as well as to environmental factors. Most rice cultivars from the Regencies of Jember and Situbondo carry Xa10 and Xa13 resistance genes.

AGRONOMIC MANAGEMENT OF BACTERIAL LEAF BLIGHT OF RICE (ORYZA SATIVA L.) DISEASE AND YIELD ENHANCEMENT THROUGH DIFFERENT COMBINATIONS OF NITROGEN AND POTASH DOSES

This research trial was conducted at Rice Research Institute, Kala Shah Kaku, during kharif 2010, to assess the influence of nitrogen (N) and potash (K) on the incidence and severity of Bacterial leaf blight of rice (BLB) (Oryzae sativa L.). The experiment was laid out in a Randomized Complete Block Design in factorial arrangement with three replications using net plot size of 2.25 m × 6.0 m. The experiment was comprised of 0, 75, 100, 125 kg N ha-1 and 0, 50, 75, 100 kg K ha-1. Thirty days old nursery of Super Basmati was transplanted manually in puddle field. Data on disease severity and yield parameters of rice were recorded using standard procedures. Yield parameters were affected significantly by various combinations of N & K. In case of BLB, minimum diseased leaf area (15.76 % DLA) was observed where N alone was applied @ 75 kg ha-1 in contrast to 125 kg N + 50 kg K ha-1 which showed maximum DLA (43.17 %). Highest paddy yield of 4.32 t ha-1 was recorded where rice was fertilized @ 75 kg N + 100 kg K ha-1, while the minimum paddy yield of 2.40 t ha-1 was obtained where only 75 kg K ha-1 was applied. Optimum fertilization @ 75 kg N + 100 kg K ha-1 improved the harvest index value up to 20.32 %. Minimum harvest index of 15.61 % was obtained where K alone was applied at the rate of 100 kg ha-1. Maximum gross income (Rs.154652 ha-1), net return (Rs.154652 ha-1), and BCR (1.32) were obtained where rice crop was fertilized @ 75 kg N and 100 kg K ha-1.

Severity of Xanthomonas axonopodis leaf blight on eucalypt cuttings under different levels of nutrients

SummaryBacterial leaf blight of eucalypt, caused by Xanthomonas axonopodis, occurs mainly in forest nurseries, but also affects young plants in the field. Avoidance of leaf wetness for long periods of time over the whole nursery and using drip irrigation for clonal hedges are, currently, the most effective measures for controlling bacterial leaf blight on eucalypt. However, as these techniques are very costly, alternative management measures are required. We hypothesized that the management of mineral nutrients could reduce disease severity on eucalypts. To examine this hypothesis, rooted cuttings of Eucalyptus urophylla × E. grandis were irrigated with nutrient solutions containing different concentrations of copper (Cu), boron (Bo), potassium (K), calcium (Ca) and nitrogen (N) before inoculation with X. axonopodis 30 days after starting the nutrient solution treatments. Concentration of K higher than that recommended, commonly used in miniclonal hedges, reduced the severity of bacterial leaf blight. However, disease severity increased with an increasing of N/K ratio. The management of mineral nutrition solution, especially K, has great potential for integrated disease management of X. axonopodis in eucalypt nurseries.

PATOGENISITAS ISOLAT BAKTERI Xanthomonas oryzae pv. oryzae DAN PEMANTAUAN PENYAKIT HAWAR DAUN BAKTERI PADA PADI GALUR ISOGENIK

Bacterial leaf blight (BLB) caused by Xanthomonas oryzae pv. oryzae (Xoo) is an important rice disease due to its high intensity that and the mereased durability of its resistant variety. This study was aimed to determine the pathogenicity of Xoo isolates, which obtained from four regions/districts in West Java on three rice near isogenic lines (NILs) containing a single resistance (R) gene; and to study reaction of rice NILs/ differential genotypes containing mixture of resistant genes to Xoo population under endemic areas. Out of 22 Xoo isolates have been collected and further determined by ELISA assay. Ten Xoo isolates were selected and inoculated to identify their pathogenicity on three NILs i.e., IRBB5 (xa5), IRBB7 (Xa7) and IRBB21 (Xa21). Pathogenicity test showed that most of isolates produced large lesion, and four virulence groups were identified. Phylogenetic analysis suggested that the dominant virulent isolates were widely distributed at several district in West Java. It was shown that 11 NILs exhibited high levels of resistant reaction to the predominant Xoo pathotypes in Cianjur, while 10 lines were susceptible. The single R gene (IRBB7, IRBB21 and Java14) exhibited lower BLB severity. The IRBB50, IRBB51, IRBB52, IRBB53 lines (carrying two R genes), IRBB56, IRBB57 (carrying three R genes); IRBB64 (carrying four R genes), and IRBB66 (carrying five R genes) showed lower severity and thus produced higher resistance to Xoo. This study may implied further work to deploy effective R genes against certain Xoo pathotypes in differ region.

Evaluation of Rice Varieties against Multiple Diseases Under Middle IGP of Bihar

An investigation was carried out to evaluate the susceptibility of rice cultivation to major field diseases like brown spot, sheath blight and bacterial leaf blight under middle Indo Gangetic Plain. The disease incidence and disease severity were observed at three different growth stages namely flowering, milk and maturity in boro seasons during 2015-16. The incidence of brown spot ranged from 8.93 to 17.83%, 16.67 to 25.67% and 18.33 to 28.33% at flowering, milk and maturity stages, respectively. The severity of brown spot in grade (0-9 scale) ranged from 5.13 to 10.33, 9.33 to 20.00 and 11.57 to 22.67, respectively at flowering, milk and maturity stages. The incidence of sheath blight of paddy ranged from 7. 03 to 16.50%, 13.13 to 22.67% and 19.67 to 35.67% at flowering, milk and maturity stages, respectively. The severity of sheath blight in grade (0-9 scale) ranged from 4.00 to 8.60, 8.33 to 13.93 and 18.33 to 34.33, respectively at flowering, milk and maturity stages. The incidence of bacterial leaf blight ranged from 5.00 to 14.00%, 11.43 to 21.00% and 17.00 to 34.00% at flowering, milk and maturity stages, respectively. The severity of bacterial leaf blight in grade (0-9 scale) ranged from 2.00 to 8.00%, 6.33 to 12.05% and 14.47 to 20.17%, respectively at flowering, milk and maturity stages. Among the varieties, the highest incidence and severity of Brown spot was recorded on Rajendra Bhagawati whereas it was lowest on 27P31 at all growth stages. In the case of Sheath blight, highest incidence and severity was recorded on Sambha Mahsuri whereas it was the lowest on CRL 193. Beside this in the case of Bacterial leaf blight, the highest incidence and severity was recorded on Kranti whereas the lowest was recorded on CRL 193. In general, it was observed that the incidence and severity of diseases increased gradually from flowering to maturity stage and the genotypes with the minimum incidence and severity of diseases gave the maximum yield.

Interactive Effect of Different Nitrogen and Potash Levels on the Incidence of Bacterial Leaf Blight of Rice (<i>Oryza sativa L.</i>)

An experiment was conducted at Rice Research Institute, Kala Shah Kaku in 2010 during kharif season to study the influence of nitrogen (N) and potash (K) on severity of Bacterial leaf blight (BLB) of rice (Oryza sativa L.) aimed at improving productivity. The experiment was laid out in randomized complete block design with factorial arrangement with three replications. Treatments comprised of: 0 kg N ha-1, 75 kg N ha-1, 100 kg N ha-1, 125 kg N ha-1 and 0 kg K ha-1, 50 kg K ha-1, 75 kg K ha-1, 100 kg K ha-1. Data on disease severity and paddy yield were recorded using standard procedures. Paddy yield was affected significantly by various combinations of N & K. In case of bacterial leaf blight, minimum diseased incidence percentage was observed when nitrogen alone was applied @ 75 kg·ha-1 in contrast to fertilizer applied @ 125 kg N ha-1 + 50 kg K ha-1 which showed maximum diseased incidence percentage. Maximum paddy yield (4.32 t·ha-1 ) was recorded when rice was fertilized @ 75 kg N ha-1 + 100 kg K ha-1 as compared to sole fertilization of 75 kg K ha-1 that produced minimum paddy yield (2.40 t·ha-1). Maximum gross income, net returns and benefit cost ratio were obtained where rice crop was fertilized @ 75 kg N ha-1 and 100 kg K ha-1.