Prevalence of Bacterial Leaf Spot of Bottle Gourd and Pumpkin in Subtropical Zone of Himachal Pradesh

Abstract

To assess the prevalence and severity of bacterial leaf spot on bottle gourd and pumpkin, a survey was conducted in Hamirpur, Una and Bilaspur districts of sub tropical zone of Himachal Pradesh, India during the years 2018 and 2019. Data were recorded in terms of disease severity and fruit rot incidence. The associated pathogen from bottle gourd and pumpkin was isolated on nutrient sodium chloride agar medium and identified on the basis of morphological, biochemical and pathogenicity tests on bottle gourd and pumpkin seedlings. Disease was found to be prevalent at all the locations surveyed exhibiting a mean disease severity from 24.70 to 87.55 and 5.30 to 52.92 per cent in bottle gourd and pumpkin, respectively. Fruits of bottle gourd were recorded to be affected badly exhibiting a mean fruit rot incidence of 10.23 to 95.32 to per cent, while, no fruit rot incidence was recorded in pumpkin fruits. The colonies of the isolated bacterium were mucoid, circular, smooth textured and yellow in colour having a diameter of 2-4 mm. The pathogen was found to be Gram–ve and tested positive for esculin hydrolysis as well as protein digestion test. During pathogenicity tests, incubation period of 2 and 4 days was recorded on bottle gourd and pumpkin, respectively. Based on these studies, the identity of the pathogen was confirmed to be Xanthomonas cucurbitae(ex Bryan) Vauterin et al.

Effect of Inoculum Density and Methods of Inoculation on the Development of Bacterial Leaf Spot of Bottle Gourd and Pumpkin caused by Xanthomonas cucurbitae

“…The results were in accordance with findings of many workers who have reported that a bacterial concentration of 10 5 to 10 8 cfu/ml is able to incite pathogenic reaction in different cucurbit hosts. (Pruvost et al, 2009;Lamichhane et al, 2010;Jarial et al, 2011;Babadoost and Ravanlou, 2012;Dutta et al, 2013;Trueman et al, 2014). During present studies, syringe inoculation method proved best for the initiation and development of the disease, followed by pin prick and leaf margin methods of inoculation in both bottle gourd and pumpkin isolates of the pathogen.…”

“…Significant losses have been reported in different cucurbits due to this disease. In bottle gourd, significant (20-70 %) losses have been reported by Larazev ( 2009), Jarial et al, (2011) and Basit et al, (2014) while in pumpkin, Salamanca (2014) reported up to 90 per cent losses.…”

“…Many workers have conducted pathogenicity experiments on artificial inoculation of this bacterium by using different methods of inoculations and various inoculum densities (Robbs et al, 1972Taketani et al, 1976El-Hendawy, 1999Pruvost et al, 2008Zitter, 2009 andJarial et al, 2011), but proper studies on appropriate method of inoculation as well as optimum inoculum density have never been conducted.…”

Cultural Parameters of Xanthomonas cucurbitae Causing Bacterial Leaf Spot of Bottle Gourd and Pumpkin

“…X. campestris pv. cucurbitae) causing bacterial spot is emerging as an important pathogen leading to huge crop losses especially to bottle gourd, pumpkin and squashes (Jarial et al, 2011;Babadoost, 2012;Babadoost, 2017). This disease was first reported as bacterial leaf spot on Hubbard squash in New York in 1925 by Bryan (Bryan, 1930).…”

“…and on bottle gourd (Jarial et al, 2011;Jarial et al, 2015;Sharma, 2016) from different countries of world.The disease has been reported to cause significant losses in different cucurbits. According to Larazev (2009), yield losses reach more than 20% in susceptible cultivars however, the disease severity reaches up to 50-60% at fruit storage in various cucurbits.…”