Loading...
Thesis
Browse
3 results
Search Results
ThesisItem Open Access Studies on Management of White Mold [Sclerotinia sclerotiorum (Lib.) de Bary] of French Bean (Phaseolus vulgaris L.)(SKUAST-K, 2003) Ahanger, Farooq Ahmad; Dar, G. H.White mold disease is one of the major diseases adversely influencing the growth and yield of French bean in Kashmir. Studies on management of white mold [Sclerotinia sclerotiorum (Lib.) de Bary] of French bean (Phaseolus vulgaris L.) were undertaken during 2002-2003 at Shalimar Campus, Srinagar, Kashmir. The diseased plants showed characteristic water-soaked lesions, white fluffy mycelial growth, formation of black sclerotia, wilt and die-back symptoms. The pathogen associated with the disease was isolated, morphologically characterized and identified as Sclerotinia sclerotiorum (Lib.) de Bary. The sclerotia formed in culture and on naturally infected plants showed some variation with respect to size shape and colour. Cold treated sclerotia (incubated at 41 0C for seven weeks) and those buried in soil at 3 cm depth showed the emergence of stipes but failed to develop apothecial discs. The bioassay revealed that all the biocontrol agents tested, except Pseudomonas fluorescen, were highly antagonastic. All biocontrol agents inhibited the radial mycelial growth and sclerotial production and myceliogenic germination of S. sclerotiorum when compared to check. T. harzianum isolates L, and P were most effective and mycoparasitized the pathogen. Gliocladium roseum and T. viride except local isolate L showed zone of inhibition in dual culture. In vitro evaluation of the fungitoxicants revealed that penconazole 10 EC had maximum inhibitory effect on mycelial growth, sclerotial production and myceliogenic germination of the test pathogen followed in order by carbendazim 50 WP> thiophanate-methyl 70 WP >mancozeb 75 WP> captan 50 WP > chlorothalonil 75 WP. Amongst the botanical extracts tested 50 per cent ehtanol-based garlic (Allium sativum) and datura (Datura. stramonium) extracts were highly effective in inhibiting mycelial growth, sclerotial production and myceliogenic germination followed by their 25 per cent ethanol-based extracts. 25 per cent aqueous extracts of mentha proved least effective. Ethanol-based botanical extracts performed better than aqueous extracts in suppressing pathogenic growth and development. Seed treatments with penconazole 10 EC (@ 0.1%) and carbendazim 50 WP (@ 0.1%) were most effective in improving seed germination followed by 50 per cent ethanol-based garlic extract and T. harzianum isolate L. The above treatments also exhibited least seedling mortality/damping-off and wilt which ranged from 6.66 to 10.00 and 5.00 to 8.66 per cent, respectively. In field trial, irrespective of foliar spray fungitoxicants, seed treatment with penconazole 10 EC was highly effective followed by carbendazim 50 WP, 50 per cent ethanol-based garlic extract and T. harzianum isolate L in improving seed germination and reducing the seedling mortality and disease incidence and severity. It was obser-ved that, irrespective of foliar sprays, seed treatment with penconazole 10 EC was highly effective followed by carbendazim 50 WP and 50 per cent ethanol-based garlic extract and T. harzianum isolate L in inhibition of white mold disease incidence on plants, leaves and pods and severity on plants in comparison to their respective checks. Seed treatment with 50 per cent ethanol- based garlic extract and T. harzianum isolate L were statistically at par with each other in controlling disease incidence and severity. However, garlic treatment was statistically identical to carbendazim 50 WP in reducing disease incidence on pods. Similarly, irrespective of seed treatments, foliar sprays with penconazole 10 EC proved significantly superior over carbendazim 50 WP in checking the disease incidence and severity on plant. Interaction between seed treatments and foliar sprays for disease incidence and severity was non-significant. It was observed that seed treatment followed by foliar sprays of penconazole 10 EC and carbendazim 50 WP were highly effective in checking white mold disease incidence and severity in comparison to seed or foliar treatments alone.ThesisItem Open Access Studies on needle blight disease of Blue pine (Pinus wallichiana Jack.) in Kashmir(SKUAST Kashmir, 2011) Ahanger, Farooq Ahmad; Dar, G HStudies were conducted on the etiology, epidemiology and management of needle blight of Blue pine (Pinus wallichiana) seedlings during 2008-2009 at Shalimar campus, Srinagar, Kashmir. The disease was prevalent in all the three surveyed districts of Kashmir viz. Anantnag, Baramulla and Srinagar with disease incidence of 31.11 and 28.83 per cent in nurseries and 42.85 and 35.84 per cent in plantations during 2008 and 2009, respectively. The average disease intensity in respective years in nurseries and plantations was 19.93 and 14.51 and 27.44 and 23.92 per cent, respectively. Lophodermium needle blight disease was characterized by the appearance of chlorotic patches which turned reddish brown with straw coloured centre surrounded by yellow halo. Infection at needle tip resulted in dieback. Severe infections caused the death of entire needle and premature defoliation. Characteristic black stromatic zone lines across the needle surface appeared in June-July. Fungal fructifications (pycnidia and hysterothecia) appeared on the infected intact and fallen needles during July to October. The hysterothecia with prominent longitudinal slits were usually formed on abaxial surface of needles. The Leptrostroma state (anamorph of Lophodermium pinastri) 8 isolated in culture was unable to cause pathogenecity on both attached and detached Blue pine needles. The fungus proved pathogenic only when ascospore suspension was inoculated on Blue pine seedlings and detached needles. The pathogen associated with the disease on morphological characters was identified as Lophodermium pinastri Chiv. The pathogen exhibited maximum radial mycelial growth and pycnidial formation on PDA, Richards and Malt extract media. The host range of Lophodermium pinastri in various conifer plants revealed that all the conifer species (Pinus wallichiana, P.halepensis, Abies pindrow, Cedrus deodara, Cuprussus torulosa, Picea smithiana and including one Cryptomeria species) reacted positively except Thuga orientalis. The ascospore release and germination of Lophodermium pinastri under in vitro conditions varied significantly at different test temperatures with highest ascospore release and germination at 25°C. The ascospore release occurred in relative humidity regimes of 60 to 100 per cent only with highest ascospore release and germination at 100 per cent RH. The disease appeared in February and reached maximum by the end of October. During the study period maximum logrithemic infection rate of 0.0618 and 0.0285 unit/day was recorded during the first fortnight of April in 2008 and 2009, respectively. Weather factors viz. temperature and relative humidity were positively correlated with disease intensity (62.1 per cent contribution). However, except temperature all other weather factors were positively correlated with the disease development in terms of infection rate (units/day) (25.7 per cent contribution). The pathogen perpetuated in the form of pycnidia and hysterothecia on fallen diseased needles. The fungal fructifications (pycnidia and hysterothecia) and their viability decreased with increase in the depth of placement in forest litter. Maximum fructifications on pine needles were observed at ground surface (0 cm depth). The diseased needles kept at 0 cm litter depth exhibited maximum hysterothecial formation and ascospore production and greater viability. Conidiomatal formation and conidial production of L. pinastri occurred in the 2nd fortnight of August and in 1st fortnight of September in the year 2008-2009 and 2009-2010, respectively. However, hysterothecial formation, ascospores production and their viability decreased significantly with increase in burial depth in forest litter. Non-systemic fungitoxicants, tested at various concentrations significantly inhibited the mycelial growth and ascospore germination of the pathogen by 52.31 to 76.34 and 60.50 to 82.21 per cent, respectively. Hexaconazole 5 EC proved superior over all other systemic fungitoxicants tested followed by flusilazole 40 EC and carbendazim 50 WP. The studies on in vivo evaluation of most effective fungitoxicants under mist- and poly-chamber conditions at three relative humidity regimes revealed that disease incidence and intensity were comparatively higher in mist- than in poly-chamber. In both, mist- and poly-chambers the Blue pine seedlings treated with hexaconazole 5EC (@ 0.03%) or carbendazim 50WP (@ 0.1%) treated seedlings had significantly less disease incidence and intensity. Increase in humidity regime from 60 to 100 per cent significantly enhanced needle blight disease incidence and intensity. All the fungitoxicants used as either single spray or protectant followed 9 by systemic fungitoxicant spray significantly reduced the disease incidence and intensity as compared to check. The mean disease intensity in fungitoxicant treated Blue pine plants varied from 3.68 to 11.70 per cent as compared to 26.66 per cent in check. Among the fungitoxicants tested mancozeb 75 WP (@0.3%) followed by 2nd spray with carbendazim 50 WP (@0.1%) or hexaconazole 5EC (@0.03%) proved superior in reducing the disease incidence and intensity on Blue pine plantations or spraying with chlorothalonil 75WP (@0.3%) followed by 2nd spray with carbendazim 50 WP (@0.1%) or hexaconazole 5EC (@0.03%) was effective in minimizing disease incidence and intensity. Two-spray treatments exhibited lesser disease intensity (3.68-5.71%) and no defoliation as compared to mono-sprayed treatments which exhibited disease intensity of 8.64 to 11.70 per cent and defoliation of 1 to 10 per cent. Electrolytic leakage in infected blue pine needles was monitored by measuring the conductivity change in pine needles affected by Lophodermium needle blight disease. Highest electrolytic leakage of 345.33 μmoh/cm was noticed in pine needles having > 81 per cent of disease severity in comparison to unaffected check (181.33 μmoh/cm).ThesisItem Open Access Studies on needle blight disease of Blue pine (Pinus wallichiana Jack.) in Kashmir(SKUAST Kashmir, 2012) Ahanger, Farooq Ahmad; Dar, G.H.Studies were conducted on the etiology, epidemiology and management of needle blight of Blue pine (Pinus wallichiana) seedlings during 2008-2009 at Shalimar campus, Srinagar, Kashmir. The disease was prevalent in all the three surveyed districts of Kashmir viz. Anantnag, Baramulla and Srinagar with disease incidence of 31.11 and 28.83 per cent in nurseries and 42.85 and 35.84 per cent in plantations during 2008 and 2009, respectively. The average disease intensity in respective years in nurseries and plantations was 19.93 and 14.51 and 27.44 and 23.92 per cent, respectively. Lophodermium needle blight disease was characterized by the appearance of chlorotic patches which turned reddish brown with straw coloured centre surrounded by yellow halo. Infection at needle tip resulted in dieback. Severe infections caused the death of entire needle and premature defoliation. Characteristic black stromatic zone lines across the needle surface appeared in June-July. Fungal fructifications (pycnidia and hysterothecia) appeared on the infected intact and fallen needles during July to October. The hysterothecia with prominent longitudinal slits were usually formed on abaxial surface of needles. The Leptrostroma state (anamorph of Lophodermium pinastri) isolated in culture was unable to cause pathogenecity on both attached and detached Blue pine needles. The fungus proved pathogenic only when ascospore suspension was inoculated on Blue pine seedlings and detached needles. The pathogen associated with the disease on morphological characters was identified as Lophodermium pinastri Chiv. The pathogen exhibited maximum radial mycelial growth and pycnidial formation on PDA, Richards and Malt extract media. The host range of Lophodermium pinastri in various conifer plants revealed that all the conifer species (Pinus wallichiana, P.halepensis, Abies pindrow, Cedrus deodara, Cuprussus torulosa, Picea smithiana and including one Cryptomeria species) reacted positively except Thuga orientalis. The ascospore release and germination of Lophodermium pinastri under in vitro conditions varied significantly at different test temperatures with highest ascospore release and germination at 25°C. The ascospore release occurred in relative humidity regimes of 60 to 100 per cent only with highest ascospore release and germination at 100 per cent RH. The disease appeared in February and reached maximum by the end of October. During the study period maximum logrithemic infection rate of 0.0618 and 0.0285 unit/day was recorded during the first fortnight of April in 2008 and 2009, respectively. Weather factors viz. temperature and relative humidity were positively correlated with disease intensity (62.1 per cent contribution). However, except temperature all other weather factors were positively correlated with the disease development in terms of infection rate (units/day) (25.7 per cent contribution). The pathogen perpetuated in the form of pycnidia and hysterothecia on fallen diseased needles. The fungal fructifications (pycnidia and hysterothecia) and their viability decreased with increase in the depth of placement in forest litter. Maximum fructifications on pine needles were observed at ground surface (0 cm depth). The diseased needles kept at 0 cm litter depth exhibited maximum hysterothecial formation and ascospore production and greater viability. Conidiomatal formation and conidial production of L. pinastri occurred in the 2nd fortnight of August and in 1st fortnight of September in the year 2008-2009 and 2009-2010, respectively. However, hysterothecial formation, ascospores production and their viability decreased significantly with increase in burial depth in forest litter. Non-systemic fungitoxicants, tested at various concentrations significantly inhibited the mycelial growth and ascospore germination of the pathogen by 52.31 to 76.34 and 60.50 to 82.21 per cent, respectively. Hexaconazole 5 EC proved superior over all other systemic fungitoxicants tested followed by flusilazole 40 EC and carbendazim 50 WP. The studies on in vivo evaluation of most effective fungitoxicants under mist- and poly-chamber conditions at three relative humidity regimes revealed that disease incidence and intensity were comparatively higher in mist- than in poly-chamber. In both, mist- and poly-chambers the Blue pine seedlings treated with hexaconazole 5EC (@ 0.03%) or carbendazim 50WP (@ 0.1%) treated seedlings had significantly less disease incidence and intensity. Increase in humidity regime from 60 to 100 per cent significantly enhanced needle blight disease incidence and intensity. All the fungitoxicants used as either single spray or protectant followed by systemic fungitoxicant spray significantly reduced the disease incidence and intensity as compared to check. The mean disease intensity in fungitoxicant treated Blue pine plants varied from 3.68 to 11.70 per cent as compared to 26.66 per cent in check. Among the fungitoxicants tested mancozeb 75 WP (@0.3%) followed by 2nd spray with carbendazim 50 WP (@0.1%) or hexaconazole 5EC (@0.03%) proved superior in reducing the disease incidence and intensity on Blue pine plantations or spraying with chlorothalonil 75WP (@0.3%) followed by 2nd spray with carbendazim 50 WP (@0.1%) or hexaconazole 5EC (@0.03%) was effective in minimizing disease incidence and intensity. Two-spray treatments exhibited lesser disease intensity (3.68-5.71%) and no defoliation as compared to mono-sprayed treatments which exhibited disease intensity of 8.64 to 11.70 per cent and defoliation of 1 to 10 per cent. Electrolytic leakage in infected blue pine needles was monitored by measuring the conductivity change in pine needles affected by Lophodermium needle blight disease. Highest electrolytic leakage of 345.33 µmoh/cm was noticed in pine needles having > 81 per cent of disease severity in comparison to unaffected check (181.33 µmoh/cm).