Etiology of stem gummosis and leaf blight of bottle gourd (Lagenaria siceraria) in Punjab
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Date
2018
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Punjab Agricultural University, Ludhiana
Abstract
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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