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20165
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Subject: Plant Pathology × End date: 2016 × Start date: 2016 × Type: Thesis ×
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    ThesisItemOpen Access
    Pathogenic variability and management of fusarium wilt of chilli (Capsicum annuum L.)
    (CCSHAU, 2016) Jaywant Kumar Singh; Mehta, Naresh
    The Fusarium wilt disease caused by Fusarium spp. has emerged as a serious problem in most of the chilli growing irrigated tracts of India, leading to considerable yield losses in chilli (Capsicum annuum L.). The present investigation on cultural, morphological, pathogenic and genetic variability was carried out with twentythree isolates of Fusarium spp. collected from chilli growing areas of the country. The isolates identified belonged to F. oxysporum and F. solani based on their morpho-cultural characteristics. The average radial growth of different isolates evaluated on different media, Czapek’s Dox agar and potato dextrose agar were the most effective media supporting the mycelial growth (>75.0 mm). All the isolates exhibited variations in their colony colour, type of growth and mycelial growth. Mycelia colour among the F. oxysporum isolates varied from white to pale yellow, whereas, in F. solani the mycelial colour varied from white, cream to pale yellow. Fusarium oxysporum isolates showed undulate fluffy, concentric fluffy, filamentous fluffy, filamentous suppressed, filamentous scanty fibrous, undulate fluffy to entire fluffy type of growth, however, the F. solani isolates formed only undulate fluffy and entire fluffy type of growth. Significant variations were observed in mean size of macroconidia and micro-conidia, where the F. oxysporum isolates formed larger size conidia compared to F. solani. The average septa in F. oxysporum isolates varied from 1-3 and 1-5, whereas, F. solani isolates formed 1-5 septa. Temporal and symptomatic wilt expression starting from 1 st to 4 th week on susceptible cultivars Pusa Jwala and Arka Meghana indicated the isolates Fo5, Fo7, Fo8 and Fo10 in F. oxysporum and Fs8 in F. solani were highly pathogenic. Amplification with genera and/or species specific internal transcribed spacer (ITS) primers clearly differentiated all the isolates into F. oxysporum and/or F. solani isolates based on amplification and size of amplicons in different isolates. The diversity analyses using universal rice primers (URPs) exhibited the genetic relatedness among the twenty-three isolates varied from 0.53-0.88, i.e., 53-88 per cent with an average similarity of 71 per cent. The URP analyses differentiated Fusarium isolates into two major clusters at similarity coefficient of 0.53, i.e., 53 per cent similarity, where all the F. oxysporum isolates were clustered into major cluster A and all the F. solani isolates into major cluster B. The isolates Fo5 & Fo10 in F. oxysporum and Fs8 & Fs3 in F. solani isolates were distantly related with 48 per cent and 50 per cent genetic similarity, respectively. The in vitro and in vivo management study involving chemicals, botanicals or antagonists as well as their integration indicated that chemicals (carbendazim + mancozeb @ 0.1% or carbendazim @ 0.1%) applied as seed treatment + seedling root dip + soil application were the most effective treatments and the chilli cultivar CO-4 found effective after extensive evaluation in screen house and field, will be highly useful for the effective management of the Fusarium wilt disease in chilli.
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    ThesisItemOpen Access
    Studies on epidemiology and molecular diversity of cotton leaf curl virus (CLCuV) in cotton (Gossypium hirsutum L.)
    (CCSHAU, 2016) Chohan, Prashant Kumar; Mehta, Nareshcc
    Present investigation comprised two cultivars HS-6 and RCH 134 BG-II susceptible to CLCuV used for study on epidemiology, effect of date of sowing and spacing on the incidence of cotton leaf curl disease (CLCuD). Biochemical studies included phenol, sugar (total and reducing), tannin, protein, gossypol, chlorophyll-a & b, peroxidase and pholyphenol oxidase analysis using standard biochemical methods. Four cotton cultivars HS-6 & RCH 134 BG-II (susceptible) and H 1236 & Bunty (resistant) were used in the study. For molecular study, cotton leaves showing CLCuD symptoms were collected from different cotton growing locations of Haryana (Sirsa, Fatehabad, Hisar, Bhiwani and Jind), Punjab (Abohar, Bathinda and Fazilka) and Rajasthan (Hanumangarh and Shriganganagar). Results exhibited that disease was appeared early in season during 2013 whereas late in 2014, however, fluctuation in white fly population during 2014 did not affect CLCuD progress. Negative correlation of CLCuD was observed with T-max and T-min, whereas, RH (morning) showed positive correlation. In early sown crop, the disease appeared at later stages of crop as compared to timely and late sown crops. Overall yield of early sown crop was highest whereas, yield in late sown crop was significantly reduced in two year of study. The effect of spacing on incidence of CLCuD was not significant. Biochemical studies revealed that phenol content was high in resistant plants whereas, low in diseased plants. Tannin content was high in resistant plants as compared to diseased plants. However, gossypol and sugar (total and reducing sugar) content changes did not show any relation with CLCuD infection in plants. Protein content was increased with the age of plant. Chlorophyll (a & b) content was higher in diseased plants as compared to healthy/resistant plants. Peroxidase and Polyphenol oxidase activity was higher in healthy (0 grade) and resistant plants in comparison to the diseased plants. Molecular study revealed that primers used in molecular level study showed differences in DNA amplification. Among the 68 samples, 36 showed DNA presence in all three primers, 4 showed in Primer-1, 7 in Primer-2, 3 in primer-3 and 4 samples did not show amplification in any of the primers. Five samples showed amplification with primer-1 & 2, 5 in primer-2 & 3 and 4 samples showed presence in primer-1 & 3 only. Monomorphic results observed did not show variability in amplified DNA of various isolates. However, the presence or absence of band with particular isolate indicated complex system of analysis of host-virus-vector relation.
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    ThesisItemOpen Access
    Studies on the dry root rot of clusterbean caused by rhizoctonia bataticola (Taub.) butler
    (CCSHAU, 2016) Dhawan, Aman; Satish Kumar
    Clusterbean [Cyamopsis tetragonoloba (L.) Taub.] is an important industrial crop of India. Among the various diseases, dry root rot disease causes heavy losses every year. The dry root rot fungus R. bataticola was isolated from root rot infected clusterbean plant and the pathogenicity of the fungus was established by satisfying the Koch's postulates. Different inoculum levels of homogenized mycelial and mycelium embedded sclerotia on pre and post-emergence plant mortality of clusterbean cv. HG-365 revealed that plant mortality was directly proportional to the inoculum levels. Mycelium embedded sclerotial culture of R. bataticola was comparatively less virulent at all the inoculum levels as compared to their same level of mycelium culture. Cowpea was recorded as most favoured host for maximum pycnidia production (29.7/cm2 surface area) as compared to clusterbean (27.7/cm2 surface area). No pycnidia were noticed on cotton, okra, mung bean and urd bean plant parts. Stem of cowpea and clusterbean appeared as good substrate for pycnidia production followed by leaves. Root parts did not support the production of pycnidia on any of the tested crops. Pycnidiospores were able to produce disease symptoms on germinated seedlings of cotton, cowpea, clusterbean, okra, mung bean and urd bean. Out of sixteen clusterbean genotypes screened under screenhouse conditions in artificial inoculated disease stress conditions, none of the genotype was found resistant to R. bataticola, however, only two genotypes viz. HG-100 and HG-75 were categorized as moderately resistant with a total plant mortality of 16.7 per cent and 20.0 per cent, respectively. A minimum disease incidence of 33.3 and 39.9 per cent was recorded when the seeds were coated with bavistin followed by captan+hexaconazole. A minimum disease incidence of 36.9 and 39.9 per cent was recorded when the soils were incorporated with mustard cake followed by cotton cake. The disease control was directly proportional to the dose of VAM. A maximum of 40 per cent disease control was recorded when the soils were incorporated with 600 sporocarps/kg soil followed by 25 per cent when soils were incorporated with 500 sporocarps/kg soil. The disease control was improved by increase in the dose of soil application of T. viride. A maximum of 34.8 per cent plant disease control was recorded when the soils were incorporated with T. viride at the rate of 10g/kg soil. Seeds treated with bavistin and sown in T. viride and mustard cake incorporated soil gave a maximum of disease control of 74.8 per cent in clusterbean cv. HG-365 as compared to control whereas, seeds treated with bavistin and sown in T. viride and mustard cake incorporated soil gave a maximum of disease control of 80.8 per cent in clusterbean cv. HG 2-20 as compared to control.
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    ThesisItemOpen Access
    Variability studies in mycogone perniciosa causing wet bubble of agaricus bisporus
    (CCSHAU, 2016) Man Mohan; Surjeet Singh
    Wet bubble disease caused by Mycogone perniciosa is one of the most devastating fungal disease and causes considerable yield loses in Agaricus bisporus. The present investigation on symptomatology, morphology, physiology, chemosensitivity and genetic variability was carried out under in vitro with fifteen isolates of M. perniciosa collected from major mushroom growing areas. The symptoms induced by different isolates of M. perniciosa varied from thick stipe to sclerodermoid having brown amber coloured droplets to internal browning. These were categorized on the basis of brown amber colour droplets, gills infection and foul smell occurrence. Isolates viz., LDP, RSN and BSN1 showed the symptoms on pileus like dark brown to light brown colour, while some isolates exhibited the brown amber droplets. A wide variation in symptoms was also detected when isolates were compared with isolates from widely reported origin of geographical regions in Haryana, Punjab and Himachal Pradesh. Isolate TPN showed thick stipe, slow mycelial growth with slightly feathery, dense mycelium and lemon colony colour. While symptoms variation observed among the isolates of M. perniciosa were compared with morphological, physiological and genetic variability, it was observed that the isolates, KSN and BSN2 produced fluffy, even, very feathery and brown in colony colour was recorded fastest growing. In results 25oC was found most suitable temperature for mycelial growth of Mycogone perniciosa. While, the pH level 7.0 was found optimum for mycelial growth of the isolates studied. These two isolates viz., KSN and BSN2 were highly diversed from rest of isolates of the M. perniciosa showing wide genetic distance. On the bsasis of chemosensitivity to metalaxyl MZ among these fifteen isolates, eleven isolates of pathogen were highely sensitive but none of isolate were under less sensitive group to Mycogone perniciosa isolates. Interaction studies between Mycogone perniciosa isolates and Agaricus bisporus strains showed mycelial inhibition. The highest pair wise genetic similarity i.e., 92.0 per cent was observed between sub cluster isolates RSN and BSN1 followed by 85.0 per cent genetic similarity between isolates KSN and BSN2 of major cluster B. In future it is likely these two isolates of Mycogone perniciosa can be used in the screening programme of strains of Agaricus bisporus.
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    ThesisItemOpen Access
    Epidemiology and management of powdery mildew in wheat
    (CCSHAU, 2016) Sharma, Vipin Kumar; Karwasra, S.S.
    Powdery mildew disease caused by Erysiphe graminis f. sp. tritici is an important disease of wheat ( Triticum aestivum L.) in the north eastern region of Haryana and adjoining areas of states of Punjab and Himachal Pradesh. Studies on epidemiology and management of this disease were carried out at IIWBR, Karnal and Regional Research Station, Dhaulakuan duing rabi 2012-13 and 2013-14. Disease first appeared in hilly areas of Dhaulakuan at ear heading stage during the first week of February followed by Gurdaspur and plains of Yamunanagar at anthesis stage during the second week of February and spread to Ambala, Ludhiana, Kar nal and Kaul at anthesis, post anthesis and grain formation stage, respectively. Out of 203 entries evaluated, 37 were found resistant at both the locations. Two varieties viz., DPW 621-50 and PBW 550 while, six varieties viz., WHD 896, WHD 942, WHD 943, W HD 948 and PWD 233 showed slow mildewing behaviour at Karnal and Dhaulakuan, respectively. Increased minimum temperature and evening relative humidity collectively explained disease progression from 45 to 84 per cent at both the locations as the disease was favoured by mean temperature of 21.0 to 21.4°C at Karnal and 18.3 to 21.0°C at Dhaulakuan. Maximum, minimum temperature and evening relative humidity collectively explained disease progression from 73 to 84 per cent at both the locations. Physiological and biochemical analysis in healthy and infected leaves of resistant (DDK 1029) and susceptible (PBW 343) varieties revealed non-significant effect on total chlorophyll content in infected leaves as compared to healthy leaves of resistant variety. In suscep tible variety, stomatal conductance in diseased leaves decreased at initial stage of infection and then reduced at higher rate at all stages of disease. There was a gradual reduction in photosynthetic and transpiration rate at all the stages of infection i n both the varieties, but reduction was more in the leaves of susceptible. In susceptible variety, the reduction in photosynthetic rate was found to be less at initial stage of disease but reduced sharpl y at later stages. Total phenol contents were higher in healthy leaves of resistant variety and after infection, the total phenol content increased in resistant variety at initial stages of disease, while the decrease was less at later stage. In susceptib le variety the total phenol content continued to increase at all stages of infection. Total sugar and non reducing sugar content in both the varieties increased after infection but the increase was more in susceptible variety. Activity of PPO and POX was found to be increased in resistant variety at all the stages. In resistant variety, there was significant increase in PPO and POX activity at disease initiation thereafter slightly decreased at later stages. Among various fungicides tested, propiconazole 25% EC and tridemorph 40% SC were found most effective even at lower dose (0.05%) and controlled the disease up to 96.55 and 93.64 per cent, respectively, as compared to untreated control.