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2013 - 20182
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Subject: Plant Pathology × Author: Gurpreet Singh × Start date: 1990 × Type: Thesis ×
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    ThesisItemOpen Access
    Etiology of stem gummosis and leaf blight of bottle gourd (Lagenaria siceraria) in Punjab
    (Punjab Agricultural University, Ludhiana, 2018) Gurpreet Singh; Jain, Sandeep
    Three simultaneously occurring syndromes viz. stem gummosis and slow vine decline; quick wilting and leaf blight were deciphered in the bottle gourd fields and their primary pathogenic causes were established. All the three types of syndromes were more prevalent in south-western districts of Punjab. The incidence of stem gummosis and slow vine decline varied from 0 to 68.30 per cent and 20.57 to 67.89 per cent, whereas the severity varied from 0 to 51.22 per cent and 11.77 to 39.33 per cent in the years 2015 and 2016 respectively. The incidence of quick wilt varied from 2.33 to 57.00 per cent and 5.15 to 27.78 per cent in the years 2015 and 2016 respectively. The incidence of leaf blight varied from 35.57 to 85.15 per cent and 28.88 to 80.15 per cent whereas the severity from 11.55 to 53.33 per cent and 20.44 to 59.67 per cent in the year 2015 and 2016, respectively. Pathogenicity tests were conducted to prove Koch’s postulates and identification of organisms was done through morphological as well as molecular studies. The causal organism of stem gummosis and slow vine decline was identified as Fusarium verticillioides (Sacc.) Nirenberg. The pathogen associated with quick wilting was identified as Fusarium oxysporum Schltdl. and the pathogen associated with leaf blight was identified as Lasiodiplodia theobromae (Pat.) Griffon & Maubl. Best medium for vegetative growth of F. verticillioides was observed to be potato dextrose agar followed by czapek’s dox agar and richard’s agar while for F. oxysporium it was czapek’s dox agar followed by potato dextrose agar and richard’s agar and for L. theobromae it was observed to be potato dextrose agar followed by V8 juice agar and rye agar. None of the test genotypes showed the resistant or moderately resistant reaction against stem gummosis and slow vine decline or quick wilting whereas two bottle gourd genotypes were adjudged as the moderately resistant against leaf blight. Under in vitro evaluation of fungitoxicants, carbendazim 50 WP was found to be the most effective fungicide against Fusarium verticillioides and Fusarium oxysporum. Trifloxystrobin + tebuconazole 75% WG was found to be the most effective fungicide against Lasiodiplodia theobromae. Soil drench with carbendazim 50 WP @ 0.2 per cent along with foliar application of tebuconazole 25 EC @ 0.1 per cent three times at fortnightly interval starting from end of July proved to be the most effective against stem gummosis and slow vine decline. Against leaf blight, three foliar sprays of propiconazole 25 EC @ 0.1 % were found to be most effective against leaf blight of bottle gourd under field conditions. This is the first systematic study on stem gummosis in Punjab.
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    ThesisItemOpen Access
    EPIDEMIOLOGY AND MANAGEMENT OF ALTERNARIA BLIGHT ON SEED CROP OF CARROT (Daucus carota)
    (Punjab Agricultural University, Ludhiana, 2013) Gurpreet Singh
    Surveys conducted during 2011 and 2012 revealed that Alternaria blight of carrot was observed at all the locations on all the cultivars. The disease incidence and severity was the highest on Local varieties as compared to PAU recommended varieties. The highest disease severity was observed on local variety grown at village Bohan in district Hoshiarpur, while the lowest disease severity on Selection-21 grown at PAU Ludhiana. Alternaria radicina and Alternaria dauci were found to be associated with the disease. Alternaria radicina has highest frequency than Alternaria dauci on carrot plants. Maximum colony growth and sporulation of Alternaria radicina was observed on carrot leaf agar followed by unmbel extract agar medium. Lowest colony growth and sporulation was observed on Czapek‟s Dox agar medium. Maximum colony growth and sporulation was observed at 25°C temperature followed by 30°C, whereas no colony growth was observed at 35°C. Most suitable range of temperature was found to be 25 to 30°C. Maximum colony growth of Alternaria radicina was observed at pH 6, whereas maximum sporulation was observed at pH 7. The disease severity increase with the increase in the age of plants and a positive correlation between plant age and disease severity was observed. Similarly disease severity increased with the increase in the leaf wetness period. A positive correlation was found between leaf wetness period and disease severity. A minimum 8 hr of leaf wetness was required to cause infection on carrot plants. All three non systemic fungicides proved less effective than systemic fungicides. Among systemic fungicides ED50 values for difenconazole and propiconazole was less than 1μg/ml, while for hexaconazole and azoxystrobin was 1.0 and 5.9 μg/ml respectively. Among non systemic fungicides ED50 value was 17 for chlorothalonil, whereas it was 44 μg/ml for mancozeb. Under field conditions all systemic fungicides proved highly effective in controlling the disease as compared to non systemic fungicides. Azoxystrobin + Difenconazole @ 0.1 per cent proved most effective in checking the disease than other tested fungicides.