Effectiveness of bioactive compounds in amending the soil infested with soil-borne Ralstonia solanacearum of potato

Three natural bioactive compounds, viz. cow dung, bee propolis and turmeric powder were applied to amend the Ralstonia solanacearum infested soil of potato. Sun dried cow dung @ 30 t/ha, aqueous extraction of turmeric powder @ 30 kg/ha and propolis @ 5 lit/ha were applied to the inoculated soil by mixing with field soil in SAU (Dhaka) and BARI (Gazipur). Data on pH, organic matter, total cfu/ml and avirulent cfu/ml of the treatment applied soil and per cent disease index (PDI) of bacterial wilt of potato were recorded. Significant difference in soil pH and per cent organic matter (OM) occurred in all the amended soil as compared to control. A decreased total cfu/ml of R. solanacearum occurred in all the treated soil, but propolis (8.2 X 107) and cow dung (1.1 X 108) showed the lowest count. However, in increasing the avirulent count of R. solanacearum, turmeric powder (1.8 X 109) showed the highest count compared to other amended soil. Significant disease reduction over control was also observed in all the treatments, but propolis (45.65%) and turmeric powder (43.48%) showed the best results in wilt disease reduction. J. Biodivers. Conserv. Bioresour. Manag. 2021, 7(1): 43-50

Exploration of Soil and Weather Factors on Mulberry Root Rot Incidence in the Western Zone of Tamil Nadu, India

Aims: To record the occurrence of mulberry root rot disease, epidemiology, interaction of weather and soil parameters with the soil-borne pathogens in Western zone of Tamil Nadu during 2019-2020. Study Design: Survey. Place and Duration of Study: Surveyed in Coimbatore, Tiruppur, Erode, Dharmapuri and Krishnagiri districts of Tamil Nadu. Laboratory experiments were carried out at Department of Sericulture & Department of Plant Pathology, Tamil Nadu Agricultural University (TNAU), Coimbatore between July 2019 and Jan 2021. Methodology: Per cent disease incidence of root rot was recorded in all surveyed gardens. To analyze the soil and weather parameters, the composite soil samples were subjected to textural analysis and weather data were collected from TNAU Agro Climate Research Centre. To predict soil temperature for all surveyed locations, the model regression equations were derived. The correlation analysis was done between per cent disease incidence, weather and soil parameters. Results: The highest disease incidence was recorded in Nallampalli block of Dharmapuri district (54 per cent) whereas the lowest in Udumalaipettai block of Tiruppur district (0.06 per cent). The infected mulberry root samples yielded complex of soil-borne pathogens including Macrophomina phaseolina, Lasiodiplodia theobromae, Fusarium sp., and pathogenicity was proved. The results revealed that root rot incidence was recorded in all types of cultivars, significantly in ruling variety V1 irrespective of its age, soil type, spacing, and irrigation method. Soil parameters like texture, temperature and moisture content were found to augment the disease. Per cent disease incidence had significantly positive correlation with the weather factors like air and soil temperature whereas negative correlation with relative humidity and rainfall. Conclusion: Synergism of abiotic stress factors hinders the mulberry plant health and increases its susceptibility to the soil-borne pathogens.

Significance of Sowing Dates and Meteorological Parameters on Severity of Stem Gall of Coriander Caused by Protomyces macrosporus

Background: Coriander (Coriandrum sativum L.) belongs to family Apiaceae is generally grown in winter season as a main crop in India. Stem gall of coriander caused by Protomyces macrosporus L. is a serious disease damaging all aerial plant parts. Under favourable ecological conditions, the disease may lead losses to the extent of 100 per cent therefore it is necessary to investigate the epidemiology of the disease to devise suitable remedial measures Methods: The field experiment was conducted during Kharif season of 2018 with two varieties to study the effect of different meteorological parameters on stem gall of coriander at different sowing dates (1st week of November to 1st week of December). The stem gall severity was recorded at weekly intervals from the start of its incidence. Result: The disease severity was lowest (5.42%) in the variety DH-36 sown in 3rd week of November and maximum disease severity (11.88%) was observed in variety DH-228 sown in 1st week of December. The quantitative relationship between the disease severity and weather variables at different dates of sowing for two varieties was obtained by performing correlation analysis. The temperature (maximum and minimum) and sunshine hours had positive correlation with per cent disease intensity, while relative humidity (morning and evening) and remaining weather parameters were non-significant at each dates of sowing but correlated with the disease intensity.

Influence of weather parameters on alternaria leaf blight severity of makhana under the agro-climate of Koshi region of Bihar

Weather parameters play a pivotal role in the infection process and spread of pathogen. It also influences the expression of susceptibility/resistance of the host plant during post-infection phases. Therefore, an experiment was conducted for two consecutive cropping seasons (2018 &2019) to study the influence of weather parameters such as temperature, humidity, rainfall and wind direction on the emergence of alternaria leaf blight of makhana in Koshi region of Bihar. Maximum per cent disease severity of alternarialeaf blightwas observed during the peak monsoon months (June to August). Highest disease severity of leaf blight (14.80% & 15.7%) was observed in the mid June during crop season, 2018 and 2019. High temperature (36.9oC & 38.1oC), and relative humidity (94% & 96.4%) of both the year 2018 and 2019 were found correlated with higher severity to alternaria leaf blight. Similarly average HTR values (3.1) were also found correlated with the average high temperature and relative humidity of both years (2018 and 2019) in terms of severity of leaf blight disease. Maximum temperatures, relative humidity and rainfall exhibited strong positive linear relationship and influenced the occurrence of alternaria leaf blight disease significantly. We also developed a geo-phytopathological model for the prediction of alternaria leaf blight disease of makhana on the basis of congenial mean temperature and relative humidity.

Screening of Tuberose Cultivars against Leaf Spot (Alternaria polyanthi) and its Management

Background: Tuberose flower has been found to be affected by various fungal and viral diseases which affect growth and cause loss in flower yield. Among them, leaf spot incited by Aternaria polianthi is an important fungal disease in tuberose. The incidence of the disease is common in the both single and double-type tuberose varieties due to prevalence of high rainfall and humid conditions. During survey it was found that the disease incidence was increasing gradually causing economic losses in Assam. Methods: The field trial was carried out during kharif seasons (2015 -18) to test the efficacy of six fungicides against leaf spot of tuberose (Var. Local single petal) caused by Alternaria polyantha. Four sprays with fungicides at an interval of seven days starting from the first appearance of the disease symptom were done. Per cent disease incidence (%) with growth parameters were recorded one week after the last spray. Another field experiment for screening the resistant genotypes was conducted using 11 tuberose genotypes during kharif seasons (2016-17 and 2017-18). Result: Eleven tuberose cultivars (Bidhan Ranjani-1, Bidhan Ranjani-2, Arka Nirantara, GK-TC-4, Prajwal, Phule Rajani, Local Single, Local Double, Vaibhav, Suhashini and Shringer) were screened against leaf spot caused by A.polyanthi under natural field condition. None of the cultivars were found to be immune or resistant, while three cultivars viz., GK-TC-4, Bidhan Rajani-1 and Arka Nirantara showed moderate resistant reaction with recorded per cent disease incidence of 16.11, 18.17 and 18.71, respectively. Spraying with azoxystrobin, difenoconazole and a combo fungicide consisting of iprodione (25%) + carbendazim (25%), at 0.1% recorded lowest per cent disease incidence of 7.91, 9.83 and 11.85% compared to control (33.62 PDI) with per cent disease reduction of 70.59%, 64.61% and 76.31%, respectively.

Effect of different inoculum levels of P. arborescens in disease development and yield losses of opium poppy

Downy mildew (DM) caused by Peronospora arborescens is the most alarming disease of opium poppy which hampered the production of opium crop in major growing areas of India. The pooled data taken from Rabi 2016-17 and 2017-18 demonstrated that chemical protected un-inoculated plot had a minimum per cent disease severity (9.83) with maximum dry latex yield (31.25 kg ha-1), seed yield (801.31 kg ha-1) and husk yield (889.66 kg ha-1). However, plots inoculated with Peronospora arborescens at high inoculum density of 9×105 spores ml-1 had considerably higher per cent disease severity (67.00) and minimum dry latex yield (6.94 kg ha-1), seed yield (548.42 kg ha-1) and husk yield (590.86 kg ha-1) with maximum 77.79,31.56 and 33.58 per cent loss as compared to un-inoculated chemical protected plot, respectively. The severity of the downy mildew disease was found to rise in direct conflict with the level of inoculum concentration with significant reduction in dry latex yield, seed yield and husk yield.

Response of cotton genotypes against the incidence of Alternaria leaf blight of cotton under field conditions

Aim: To identify the resistant source present in the breeding materials against Alternaria leaf blight disease of cotton (Gossypium spp.). Methodology: Breeding entries were sown in a randomized complete block design in the experimental site. Disease intensity on each genotype at 45, 90, 135 and 180 days after sowing (DAS) were recorded from leaves of lower, middle and upper parts of plants and graded. According to 0 - 4 disease scoring scale, per cent disease index (PDI) was calculated and genotypes were categorized into different categories based on disease reaction Results: Development of Alternaria disease was noticed at early days of crop growth in few genotypes and the disease increased upto 135 days after sowing. The maximum mean per cent disease index of 41.17 and 40.06 were recorded in Br.14a (ZT)1333 and Br.14a (ZT)1332 respectively. The least PDI of 0.58 was recorded in Br.03a (ZT)1303. Disease incidence of <11.00% of was reported in 37 entries at 45 days after sowing. None of the genotypes showed apparently immune reaction, twenty-one genotypes showed resistant reaction, eleven genotypes were moderately resistant and five showed moderately susceptible reaction. Interpretation: Twenty-one breeding lines showed resistant reaction against Alternaria leaf blight disease under field conditions, however, further utilization of these lines may be carried out in breeding programmes for the development of resistant source against this disease.

Field Efficacy of Thiophanate Methyl 44.8% + Kasugamycin 2.6% Sc against Major Foliar Diseases of Tomato

Tomato (Solanum lycopersicum L.) is the important edible solanaceous plant originated from western South and Central America. Despite botanically being a fruit, it’s generally eaten and preferred like a vegetable. Tomatoes are the major dietary source of the antioxidant lycopene, which has been linked to many health benefits, including reduced risk of heart disease and cancer. Early blight caused by Alternaria solani and powdery mildew caused by Erysiphe orontii and bacterial leaf spot caused by Xanthomonas campestris has become a serious problem for successful cultivation of tomato. Therefore, a field experiment was carried out to know the efficacy of Thiophanate methyl 44.8% + Kasugamycin 2.6% Sc on tomato diseases during 2017-18 and 2018-19, at College of Agriculture, Shivamogga. Experimental results revealed that all the treatments significantly reduced the early blight, bacterial leaf spot and powdery mildew disease severity over untreated control. Among all the treatments Thiophanate methyl 44.8% + Kasugamycin 2.6% SC @ 1250 ml/ha recorded significantly less Per cent Disease Index (PDI) of Early blight (Alternaria solani) (7.78 % and 10.19 %), Bacterial leaf spot (Xanthomonas campestris) ( 3.96 and 1.39 %) and Powdery mildew (Erysiphe orontii) ( 1.67 and 2.50 %) with yield of 340.33 and 333.33 q/ha followed by Thiophanate methyl 44.8% + Kasugamycin 2.6% SC @ 1000 ml/ha.

Survey for incidence and severity of grain discolouration of paddy in northern parts of Karnataka

A roving survey was conducted in major paddy growing areas of northern parts of Karnataka. A total five districts viz., Belagavi, Dharwad, Haveri, Koppal and Uttara Kannada were surveyed during Kharif 2017 to record the severity and incidence of grain discolouration. In all the areas surveyed, rice was grown in black and red soils under both irrigated and rainfed condition. During the survey the disease was observed at early grain filling to maturity stage. The disease severity ranged from 06.66 to 26.23 PDI and per cent disease incidence ranged from 12.21 to 46.66 per cent. The maximum severity (26.23 %) and per cent incidence (46.66 %) was recorded in Medleri village of Ranebennur taluk on Haveri district. The minimum severity (06.66 %) and per cent incidence (15.19 %) was recorded in Gundenhatti village of Khanapur taluk on Belagvi district. The maximum disease severity and incidence was observed in black soil under irrigated conditions during maturity stage.

Relative incidence of aphid (Lipaphis erysimi) and Alternaria blight on mustard in sub-mountainous region of Punjab

Aim: To study the relative incidence of mustard aphid and Alternaria blight on different rapeseed-mustard varieties to assess their resistant or tolerant and most suitable variety for sub-mountainous area of Punjab. Methodology: The experiment was conducted on four mustard varieties (RLM-619, PBR-97, PBR-357 and Giriraj) with five replications in randomized block design during two crop seasons, i.e. Rabi 2018-19 and 2019-20 under sub-mountainous areas of Punjab. Aphid population was recorded at weekly interval. Disease severity was calculated using 0-5 rating scale and per cent disease intensity was calculated. Results: RLM-619 variety exhibited the lowest aphid infestation (7.92 and 8.96%) and minimum per cent disease intensity (28.0 and 33.33%) on leaves and siliqua (33.33 and 38.33%) which also gave highest yield (739.33 kg acre-1 and 735.67 kg acre-1) during the year 2018-19 and 2019-20. The lowest seed yield (487.67 kg acre-1 and 480.67 kg acre-1) was recorded in variety Giriraj, which was found susceptible to aphid infestation and Alternaria blight. Interpretation: RLM-619 exhibited tolerance against aphid and Alternaria blight, hence, this variety may be used as a key component under integrated pest and disease management in sub-mountainous area of Punjab in future.