Cent Disease Severity Research Articles

Effect of petroleum-based oil on management of sigatoka leaf spot (Fusarium sp.) on banana (Musa sp.)

A field experiment was conducted at farmers’ fields to find out the effect of different treatments against sigatoka leaf spot caused by Mycosphaerella spp. on banana (Musa sp.) during 2014–15 and 2015–16 at KVK, Burhanpur, Madhya Pradesh, India. The experiment was laid out in a randomized block design in three replications with nine treatments. There was minimum per cent disease severity index of sigatoka (13.57%) by the treatment T8, i.e. spraying of Hexaconazole (H) @ 0.05% + petroleum based oil (Benole) @ 1% with maximum yield (69.9 t/ha), followed by treatment T7 Propiconazole(P) @ 0.05% + Petroleum based oil (Benole) @ 1% (67.33 t/ha) as compared with rest of the treatments.

Occurrence of powdery mildew disease of Gerbera in Kerala

A purposive sampling survey on the hilly tracts of Wayanad, Kerala revealed the existence ofpowdery mildew disease in gerbera crops, grown under both protected and open field condition.Among the other fungal diseases of gerbera, powdery mildew disease causes decisive damageto the ornamental cut flower crop, thereby decline in the industrial value of the crop. Symptomof the disease include as white powdery mat on the upper surface of leaf lamina that graduallyturned pale yellow to brown. Powdery mildew existed in two locations of Wayanad viz.,Ambalavayal and Chulliyode where highest per cent disease severity (PDS) of 50.72 wasobserved at Chulliyode and 47.2 per cent was observed at Ambalavayal during November-December. In Ambalavayal, the disease was non-significant and no correlation existed betweenweather parameters and disease progress. But, in Chulliyode, correlation studies revealed thatit was significant with positive correlation to relative humidity and a reverse relation existedwith temperature and rainfall. The weather data clearly depicts that at a low rainfall of 96 mmand above average relative humidity of 80.27 per cent during November-December was thecongenial factor influencing the disease development. But during summer, decline in relativehumidity (78.37%) and rainfall (63.13 mm) caused a slight reduction in mean per cent diseaseseverity of 49.12 per cent and 33.6 per cent at Chulliyode and Ambalavayal respectively.Morohological and cultural characters of the pathogen depicts presence of two distinct organismviz., Golovinomyces cichoracearum (Erysiphe cichoracearum) and Podosphaera sp. as thecausative organism of the disease. Golovinomyces cichoracearumproduced hyaline, septatemycelia with globose conidia with irregular peripheral end formed in a chain and Podosphaerasp. produced superficial, hyaline, coenocytic mycelium with oval or ellipsoidal, catenate conidiawith dimension ranging from 22.1-30.18 x 13.36-18.08ìm formed in unbranched erectconidiophores.

Occurrence of powdery mildew disease of Gerbera in Kerala

A purposive sampling survey on the hilly tracts of Wayanad, Kerala revealed the existence of powdery mildew disease in gerbera crops, grown under both protected and open field condition. Among the other fungal diseases of gerbera, powdery mildew disease causes decisive damage to the ornamental cut flower crop, thereby decline in the industrial value of the crop. Symptom of the disease include as white powdery mat on the upper surface of leaf lamina that gradually turned pale yellow to brown. Powdery mildew existed in two locations of Wayanad viz., Ambalavayal and Chulliyode where highest per cent disease severity (PDS) of 50.72 was observed at Chulliyode and 47.2 per cent was observed at Ambalavayal during November-December. In Ambalavayal, the disease was non-significant and no correlation existed between weather parameters and disease progress. But, in Chulliyode, correlation studies revealed that it was significant with positive correlation to relative humidity and a reverse relation existed with temperature and rainfall. The weather data clearly depicts that at a low rainfall of 96 mm and above average relative humidity of 80.27 per cent during November-December was the congenial factor influencing the disease development. But during summer, decline in relative humidity (78.37%) and rainfall (63.13 mm) caused a slight reduction in mean per cent disease severity of 49.12 per cent and 33.6 per cent at Chulliyode and Ambalavayal respectively. Morohological and cultural characters of the pathogen depicts presence of two distinct organism viz., Golovinomyces cichoracearum (Erysiphe cichoracearum) and Podosphaera sp. as the causative organism of the disease. Golovinomyces cichoracearumproduced hyaline, septate mycelia with globose conidia with irregular peripheral end formed in a chain and Podosphaera sp. produced superficial, hyaline, coenocytic mycelium with oval or ellipsoidal, catenate conidia with dimension ranging from 22.1-30.18 x 13.36-18.08ìm formed in unbranched erect conidiophores.

Characterization of Xanthomonas axonopodis pv. punicae (Hingorani and Singh) Vauterin et al. and Isolation of Xap Specific Bacteriophage

Bacterial blight (BLB) caused by Xanthomonas axonopodis pv. punicae (Xap) has emerged as a potential threat in pomegranate cultivation in India. To know the present disease scenario and to identify the root cause for its epidemic, survey was conducted in five different localities of Tamil Nadu. Per cent disease severity (PDS) ranged from 1 to 36 per cent on leaves and zero to 40 per cent infection on fruits. Bacteriophage or bacteria killer specific to Xap-1 (Sennampatty) isolate was isolated from pond water after enrichment of water sample. Phage produced plaques of 2 mm, 1 mm and < 1mm size that coalesced after 18 h of plating which shows virulence and rapid phage multiplication. Disease severity on test plants were studied to know the degree of virulence and variability among the isolates with highest severity of 37.31 per cent documented in Xap-1 followed by Xap-3 (28.7%) and Xap-2 (24.3%). Physiological factors such as temperature, pH and their role in growth of Xap-1 were accessed. Maximum growth was observed at 28˚C (0.86 OD) followed by 30˚C (0.68 OD) and pH 7 (1.83 OD) and optimum at 7-8 pH for virulent (Xap-1) isolate. Molecular confirmation of Xap through 16S rRNA sequencing gave the amplicon of 1500 bp size and amplification through KKM5 and KKM6 further confirmed specific identity.

Screening black gram genotypes under artificially inoculated conditions for powdery mildew resistance

An effective and durable genetic resistance in black gram genotypes against powdery mildew provides a cost effective and reliable strategy to reduce the yield losses and save quality of the harvest. The identification of potential resistant source(s) is the most crucial step in disease resistance breeding. In the present study, out of 116 genotypes screened, genotype LBG-645 recorded lowest per cent disease severity of 0.77 and was found to be highly resistant to powdery mildew under green house condition. Under in vitro condition also, LBG-645 which was found to be highly resistant with 3.33×103 conidia colony, 0.94 per cent of leaf area covered by powdery mildew and 1.00 colony per leaflet was recorded. Hence, resistant genotype LBG-645 must be used in further breeding programme for the development of resistant varieties of black gram against powdery mildew.

Influence of weather parameters on progress of rust disease severity in pea (Pisum sativum L.)

Decision to apply one or more fungicide spray will depend on the risk of rust epidemic in a particular year. Rust epidemic is determined by interaction of three important factors namely, susceptible host, virulent pathogen and the most important i.e. favourable environment for a particular period of time. Therefore, it is necessary to study the correlation between different meteorological parameters and rust severity. Present study revealed that rust dis-ease generally appeared 60 days after sowing and was subsequently increased with a period of time till harvest (4.17 to 64.17 per cent). Disease was observed at a maximum temperature of 16.85 to 24.79áµ’C, 8.09 to 12.27áµ’C minimum temperature, 90.30 to 95.70 percent morning Relative Humidity (RH), 54.80 to 78.40 percent afternoons RH, 0.10 to 5.45mm rainfall and wind velocity of 3.93 to 4.23 km/hr. The correlation between different meteorological parameters and rust severity revealed that per cent disease severity showed highly positive correlation with maxi-mum temperature (r = 0.977), minimum temperature (r = 0.704), rainfall (r = 0.039) and wind velocity(r = 0.093) whereas disease severity show negative correlation with morning(r=-0.925) and afternoon RH (r = -0.926). It was observed that the rust severity is highly influenced by the different weather parameters such as temperature, relative humidity, rainfall and wind velocity. This information will help the researchers in formulating the forecasting model for the rust disease in pea and will also supports farmers in decision making regarding time of occurrence of rust epi-demic and thereby, allow timely scheduling and need based utilization of fungicides accordingly for the management of pea rust.

Estimation of yield and grain qualities of marker assisted backcross derived lines of submergence rice against sheath blight disease

Sheath blight caused by Rhizoctonia solani is one of the most devastating diseases of rice (Oryza sativa) and causes enormous yield losses over the world after blast, the disease can cause yield loss upto 50 per cent in advanced stage and adversely affects quality of straw. Breeding for resistant varieties is the only viable option to combat the disease efficiently. In this study, our findings showed a significant increase in number of spikelet’s per panicle (3.45 %), test weight (0.62 %) and grain yield (0.72 %) compared to recurrent parent Swarna sub-1. The range of mean performance of 18 BC2F1 selected improved lines varied for per cent disease severity from 26.75 to 43.58 at 16 days after inoculation. Among the 18 improved lines, only four lines (Swarna sub-1-6, Swarna sub-1-32, Swarna sub-1-13 and Swarna sub-1-29) showed resistance score of 1-3. The remaining fourteen lines showed moderate resistance with a score of 3-5. Hence, the resistance line could be exploited in sheath blight resistance breeding programme and the same line can also be released as a variety against sheath blight of rice after testing over multilocation trails.

Evaluation of commercially available talc formulations of bioagents for management of sheath blight of rice and their effect on plant growth enhancement

The effectiveness of commercially available talc formulations of Trichoderma harzianum and Pseudomonas fluorescens applications either alone or in combination on rice crop growth, sheath blight disease and grain yield was investigated in field experiments. Seed and soil application of T. harzianum and P. fluorescens resulted in significant reduction of sheath blight disease incidence caused by Rhizoctonia solani and was comparable to the treatment with a systemic fungicide carbendazim (seed and foliar application). Lowest sheath blight severity was recorded in the treatment comprising combined application of T. harzianum and P. fluorescens (9.50%) whereas, 10.6 per cent sheath blight severity was recorded in plot receiving seed and foliar application of carbendazim. Plots having seed and soil application of T. harzianum and P. fluorescens alone had 11.5 per cent and 11.8 per cent disease severity, respectively. Observations recorded at the time of disease incidence revealed that combined application of T. harzianum and P. fluorescens delayed disease incidence by 35 days which was maximum among all the treatments. Seed and foliar application of carbendazim also delayed disease incidence by 27 days which was significantly lower than combined application of T. harzianum and P. fluorescens . Observations on plant growth parameters revealed that plant growth was maximum in plots having combined application of T. harzianum and P. fluorescens , in this treatment higher plant height (112.0 cm), shoot dry weight (32.0 g), root dry weight (7.9 g) were recorded. No significant increase in plant growth was recorded in plots receiving seed and foliar application of carbendazim. Studies on different treatments on yield attributes also established combined application of T. harzianum and P. fluorescens as the most effective treatment and resulted in 17.56 per cent increase in plant yield followed by T. harzianum (16.75%) and P. fluorescens (14.86%) alone, only 9.45 per cent increase in plant yield was recorded in plots having seed and foliar application of carbendazim.

Survey for the powdery mildew of black gram [Vigna mungo (L.) Hepper] in parts of Northern Karnataka, India.

Powdery mildew caused by Erysiphe polygoni DC is one of the major constraints in the production of black gram, which lead to a potential decrease in yield (40-90%). In order to know the severity of black gram powdery mildew, the roving survey was carried out to know the severity of the disease in five districts of northern Karnataka viz., Belgaum, Dharwad, Gadag, Haveri and Uttara Kannada districts during Kharif and Rabi season of 2012-13. Maximum mean per cent disease severity (PDI) was observed in Belgaum district (68.72%) followed by Dharwad district (59.73%), Haveri district (52.10%) and Uttara Kannada district (44.59%). Whereas, minimum per cent disease severity (PDI) was noticed in Gadag district (20.23%).

Prevalence, symptomatology, pathogenicity and nutritional requirements of Fusarium oxysporum f.sp.phaseoli causing Fusarium yellows of French bean in Thandikudi

Fusarium yellows/wilt caused by Fusarium oxysporum f.sp. phaseoli are one of the serious diseases in French bean in Thandikudi and Kodaikanal hills of Dindugal district was found to prevalent in all French beans growing areas under survey with maximum of 71.25 per cent incidence and 65.88 per cent disease severity at Thandikudi village of Dindugal district in Tamil Nadu. The pathogenicity test was conducted by artificial inoculation of test fungus into the young two leaf stage of French bean and the typical symptom were produced after twelve days after inoculation. Among the different solid and liquid media tested oat meal agar potato dextrose agar medium supported growth of the casual fungus. Fungus could grow well at a pH 4.0 and 5.0, respectively. This pathogenic fungus grew maximum when basal medium was supplemented with lactose and dextrose as carbon sources showed maximum growth and with potassium nitrate and sodium nitrate as nitrogen sources.

Effect of surfactant on the efficacy of fungicides against purple blotch of onion caused by Alternaria porri

Purple blotch of onion caused by Alternaria porri is an economically important disease. The field trials were conducted during three crop seasons in order to study the effect of surfactant on the efficacy of fungicides because the use of fungicides for the control of purple blotch of onion is less promising due to the waxy and smooth leaf surface, which does not allow the fungicides to spread and adhere properly on the leaves. Chlorothalonil 75 WP (1.5 g/l) and mancozeb 75 (2.0 g/l) when sprayed along with surfactant (0.5 ml/l) showed minimum per cent disease index (5.38 and 7.96%, respectively) and disease incidence (11.80 and 15.47%, respectively) at 15 days after third spray in comparison to chlorothalonil and mancozeb alone where the disease index was 8.93 and 11.52%, respectively, and disease incidence was 15.92 and 20.38%, respectively. The results also indicated that the efficacy of fungicides was significantly increased by adding surfactant from 23.69 to 39.75 and 19.87 to 25.88% in minimizing disease index and disease incidence, respectively, in different treatments when compared with the fungicides without surfactant. Both chlorothalonil and mancozeb along with surfactant showed minimum disease severity (9.72 and 12.36%, respectively) at 15 days after third spray and highest bulb yield (237.70 and 231.96 q/ha, respectively) as compared to both the fungicides sprayed alone. The per cent increase in bulb yield over control ranged from 5.57 to 27.60 in different treatments. The fungicides along with surfactant reduced the per cent disease severity (16.15–24.12) and increased the bulb yield (5.31–9.81%) in different treatments when compared with the fungicides without surfactant. The study clearly demonstrated the potential of surfactant to improve the efficacy of fungicides against purple blotch of onion.

Powdery mildew disease in sunflower : A review

Sunflower (Helianthus annuus L.) is one of the most important oilseed crops in the world. It is introduced in India during seventies and has occupied an important position in the oilseed economy ofthe country. The area under sunflower has reached to a maximum of 2.5 million ha during 1994 which declined drastically within the last two decades to 6.9 lakh ha (2014-15). Among the production constraints, vulnerability of the released cultivars to diseases at both vegetative and flowering stages played a major role compelling farmers to switch over to alternate crops. Of the various diseases, alternaria leaf blight, downy mildew and sunflower necrosis diseases attack the crop during vegetative stage while powdery mildew infects the crop from flowering to post flowering and seed formation stages. Powdery mildew is the economically important disease of the tropical regions but has not been witnessed on sunflower in India till the recent past. In India, powdery mildew was reported in high intensity (80%) during the year 2006-07 on rabi crop in some areas around Bengaluru and Raichur which increased over the years. Currently, the disease is observed on the crop in all growing situations viz., kharif, rabi and spring recording 30-75 per cent disease severity and causing yield losses to the tune of 20-50 per cent necessitating research for development of management strategies. Intensive researchwork on sunflower powderymildewis being carried out at Indian Institute of Oilseeds Research, Hyderabad and University of Agricultural Sciences, Bengaluru and disease management practices are being worked out at various AICRP sunflower centres. This review presents the information on the distribution, economic importance, symptomatology, epidemiology, disease cycle, sources of resistance and management strategies for powdery mildew disease on sunflower.

Biochemical Changes in Relation to Brown Leaf Spot (Drechslera oryzae) Resistance in Different Rice Genotypes

Brown leaf spot resistance in twelve rice genotypes viz IRRON M2 201, IRRON M2 202, IRRON M2 203, IRRON M2 204, IRRON M2 205, IRRON M2 302, IRRON M2 303, IRRON M2 304, IRRON M2 401, IRRON M2 402 and IRRON M2 501 were tested that the genotypes were showing 5.10 -20.16, 6.15-30.31 and 9.30-38.71 per cent disease severity at vegetative, panicle initiation and milk dough stages of plant growth, respectively which has also indicated that stages of plant growth also give variable response to disease. The mechanism of resistance revealed that the higher amount of total phenol and soluble protein in rice leaves resulted lower disease incidence. The rice genotype IRRON M2 205 is having maximum amount of soluble protein, representing 22.46, 21.94 and 21.27mg/gm and total phenol of 1.79, 1.68 and 1.61mg/gm of fresh leave at vegetative, panicle initiation and milk dough stage, respectively. Correlation between total phenol and soluble protein with disease severity at different growth stages shows that there was a negative correlation in all the rice genotypes. The rice genotype namely IRRON M2 205 was showing correlation value (r) -0.3310, -0.3415 and -0.3510 at vegetative stage, panicle initiation stage and milk dough stage, respectively. Banding pattern of protein resolving in SDS-PAGE showed that the maximum number of protein bands (13) was found in genotype IRRON M2 205. The protein banding patterns might be the responsible factors for resistance in rice against brown leaf spot pathogen.

Occurrence and distribution of bacterial blight of pomegranate caused by Xanthomonas axonopodis pv. punicae in Latur and Osmanabad districts of Marathwada region

An extensive survey was carried out during Kharif , 2010 in the month of September -October in Latur and Osmanabad districts. The different orchards of Latur, Chakur, Renapur, Ausa, Nilanga, Shirur Anantpal, Udgir, Deoni, Jalkot and Ahmedpur tahsil of Latur district and Osmanabad, Tuljapur, Lohara, Kalamb, Paranda, Bhum, Washi and Umarga tahsil of Osmanabad district of Maharashtra state were surveyed to find out the disease severity of oily spot disease of pomegranate in these orchards. The observation of per cent orchards affected, per cent incidence on tree and per cent disease severity in orchards were recorded during the survey of oily spot of pomegranate. The data collected during the survey of oily spot of pomegranate clearly indicate that the disease was present in moderate to severe form in most of the orchards of Latur and Osmanabad district, however some orchards were found free from the disease. The severity of the disease was maximum in Udgir tahsil followed by Renapur and Nilanga, whereas it was maximum in Tuljapur followed by Osmanabad and Lohara tahsils of Osmanabad district. The maximum per cent disease incidence was 80.00 per cent in Latur followed by Udgir (72.72%), Renapur (66.66%), Shirur Anantpal (60%) and Ausa (57.14%). The minimum per cent disease incidence of bacterial blight of pomegranate was found in Jalkot and Deoni i.e., 33.33 per cent. In Osmanabad district, the maximum per cent disease incidence was found in Lohara (83.33%) followed by Tuljapur (72.72%), Osmanabad (57.14%) and Washi (44.44%). The minimum per cent disease incidence of bacterial blight of pomegranate was found in Bhum (16.60%), Kalamb (33.33), Umarga (33.33%) and Paranda (37.50%).

Effect of rain simulation on Xanthomonas oryzae pv. oryzae population density in guttation fluid and on the spread of bacterial blight in rice

Bacterial blight of rice caused by Xanthomonas oryzae pv. oryzae is most serious biotic constraint of rice production in Punjab, influenced mainly by environmental factors and nutritional factors applied to the rice crop. Present study aimed at observing the relationship between rain simulation and disease spread. More number of bacterial colonies was recovered from the susceptible rice cultivar (Pusa 1121) plants where no-rain was simulated as compared to those where rain was simulated. Mean bacterial log cfu in rain simulated plant was 4.88 as compared to 5.67 in non rain simulated plots after 1day of inoculation. The population densities of bacteria increased gradually in both the treatments. The log cfu of bacteria was 5.84 in rain simulated plots as compared to 6.28 in non rain simulated plots after 7 days of inoculation. However after 14 days of inoculation, the bacterial population in guttation fluid was foundto be non-significant at 5% level of significance in rain and non rain simulated plots but the bacterial population was found to be less as compared to that after 7 days of inoculation. Rain washed off the guttation fluid which resulted in decrease of bacterial load in the infected leaf. The significant difference at 5 % level of significance was observed between the per cent disease severity and disease spread was also observed in rain simulated plots and no rain simulated plots in cultivar Pusa 1121 which is a bacterial blight resistant cultivar.

Integrated management of bacterial blight disease (oily spot) of pomegranate caused by Xanthomonas axonopodis pv. punicae

A study of efficacy of different antibiotics for management of bacterial blight disease of pomegranate caused by Xanthomonas axonopodis pv. punicae was conducted during the year 2010-12 at College of Agriculture, Osmanabad. In vitro study revealed that antibiotic streptocycline showed maximum inhibition zone of 22.21 and 31.60 per cent at 250 and 500 ppm concentrations against X. axonopodis pv . punicae , followed by tetracycline (18.26 and 27.53 %) and bacterinol (17.40 and 27.15 %) the least inhibition of bacterial growth was observed in cefaclore (13.08 and 17.53 %), respectively. Among seven botanicals neem oil showed maximum inhibition at all concentration (5, 10, 15 and 20 %) followed by garlic, neem leaf extract, tulasi leaf extract, ginger extract, guava leaf extract and aloe vera, respectively. The bacterial antagonistic viz., Pseudomonas fluorescens and Bacillus substilis were found effective in inhibiting the test pathogen at 15.43 and 12.71 per cent, respectively. Based on the efficacy of these different antibiotics, bioagents and plant extracts, the best one were applied in integrated management schedule for mitigating bacterial blight of pomegranate. The schedule was applied at five different locations in Marathwada region of Maharashtra. At the time of adoption of orchards, the per cent disease severity observed in the orchard at Kelewadi, Wagholi, Sakanewadi, Hol and Killari were 16.44, 16.56, 17.85, 11.50 and 26.32 which was reduced to 3.5, 8.23, 8.14 and 9.53 and 9.04, respectively at harvest.

Host–pathogen interactions of Brassica genotypes for white rust (Albugo candida) disease severity under aided epiphytotic conditions in India

A total of 13 strains of oilseed Brassica genotypes were evaluated for their reaction to white rust pathogen Albugo candida Pers. Kuntze during crop seasons 2007–08, 2008–09 and 2009–10 at five agroclimatically diverse locations in India. Aided epiphytotic conditions were provided to ensure heavy disease pressure at all the locations. The disease reaction of different genotypes was recorded at 100 days after sowing (DAS) as per cent disease severity based on per cent leaf area affected by the pathogen. Genotypes exhibited variable disease reaction in space and time indicating the prevalence of different isolate(s) of the pathogen. However, some genotypes like PBC 9221, EC 414299 and GSL-1 exhibited resistant reaction to white rust pathogen across the locations consistently during the three cropping seasons. Some of the genotypes showed specific resistant disease reaction at a specific location indicating their suitability for cultivation at that particular location. For example, JMM 07-1, JMM 07-2 and JYM 10 have shown specific resistance reaction to isolate(s) of white rust at Morena location. It can be concluded from the study that some of the genotypes showed resistant reaction to prevalent isolates of an area. Thus, it is advised to test the genotypes for the reaction to a particular/range of diseases for the specificity in performance, if any, before release for general cultivation in a particular area.

Biological control of mushroom brown blotch disease using antagonistic bacteria

Button mushroom brown blotch disease is one of the most important and devastating diseases in Iran which is caused by Pseudomonas tolaasii. To screen antagonistic bacteria against this pathogen, major mushroom cultivation centres in Iran were surveyed and samples were taken from compost, soil cover and button caps with or without visible symptoms. In total, 120 bacteria were isolated on the basis of their morphology and pathology on excised tissue blocks of the fresh Agaricus bisporus. Among all tested bacteria, thirty-six isolates produced variable inhibition zones and reduced the symptom incidence on tissue blocks of A. bisporus. The most effective antagonistic bacteria caused almost 100% inhibition of pathogenic bacterium. To confirm the identification of antagonistic bacteria, RNA polymerase beta-subunit gene (rpoB) of five antagonistic strains (A1, A2, A3, A4 and A6) were amplified using primer sets of long amplicon primers (LAPS) and LAP27. The polymerase chain reaction products of the strains A1, A3 and A6 were sequenced. Based on phenotypic, biochemical and molecular characteristics, the bacterial antagonists were identified as P. putida (A1), P. reactants (A2 and A6), P. fluorescens (A3 and A4) and Bacillus subtilis (A5), respectively. In all four criteria including weight of the diseased and healthy caps, per cent disease severity and per cent disease incidence, the treatment 2 (P. fluorescens A4) was the most effective from among T1, T3, T4 and T5 treatments. Overall results of this study suggest that bacterial antagonists may be potential biocontrol agents for biological promotion of the health and growth of button mushroom.

Screening of Rose Varieties Against Black Spot Disease and its Management in East Siang District of Arunachal Pradesh

Rose varieties were evaluated in field against Diplocarpon rosae, which causes of black spot disease of rose. Black spot resistance was visually evaluated for thirty seven rose varieties against D. rosae. Out of thirty seven varieties evaluated, none of the varieties were found immune, very highly resistant, highly resistant, resistant and moderately resistant. However, three varieties namely Paradise, Shabnam and Pixie showed moderately susceptible in reaction. Whereas, eleven varieties viz., Angelica Renae, Atago, Folklore, Granada, Hot Cocoa, Mardigrass, Midas Touch, Mrinalini, Revival, Tipus Flame and Victor Hugo showed susceptible reaction. Twelve varieties viz. Baccardi, Claudia Ribond, Charles Mallerin, Crimson Lace, Dr. Pal, Impatient, Madam Dulbourde, Marcopolo, Melody, Rainbow End, Sonia and Sugandha were highly susceptible reaction at 75 per cent disease severity. Whereas, eleven varieties namely Angelique, Christian Dior, Gemini, Gladiator, Golden Jubilee, Priyadarsini, Sand. Centenary, R. R. M. Roy, Sweet Promise, Unforgotten and Vale of Cloyd were highly susceptible reaction at 95 per cent disease severity. Further, five fungicides [three systemic fungicides namely Carbendazim, Hexaconazole (Contaf) and Ridomil MZ 72 WP and two contact fungicides viz. Blitox-50 and Mancozeb] were evaluated in vitro for the management of D. rosae. Hexaconazole (Contaf) was found to inhibit the mycelial growth of D. rosae significantly at a concentration of 200 and 250 ppm followed by Ridomil MZ 72 WP at same concentration.

Area under disease progress curve and apparent infection rate of Alternaria blight disease of Indian mustard (Brassica juncea) at different plant age

Plant age has a major influence on the incidence of Alternaria blight disease in Indian mustard crops. Disease progression was monitored twice a week on the two chosen Indian mustard cultivars viz., Varuna and Rohini throughout the season. Severity of blight caused by Alternaria brassicae and Alternaria brassicicola decreased with delay in sowing. Calculation for A-value (Area under disease progress curve – AUDPC) and r-value (apparent infection rate) in crops sown on different dates could identify the speed of progress in the disease on leaves and pods, as the crop does not posses resistance to the pathogen till date. Thus, the probable dates of sowing enabling slow disease progress or the weather conditions coinciding with the different crop phenological stages demarcated the advantageous dates of sowing from the disadvantageous ones. However, cultivar Varuna is more susceptible as compared to the other cultivar Rohini, as apparent infection rate both on leaves and pods was higher in former. Highest per cent disease severity (PDS) for season highly correlated with date of sowing, i.e. delayed date of sowing increased PDS.