Biological control of Sclerotinia sclerotiorum causing stem rot disease of sunflower using bacterial endophytes
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Date
2023
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Punjab Agricultural University, Ludhiana
Abstract
The aim of present study was to screen antagonistic bacterial endophytes against Sclerotinia sclerotiorum causing stem rot disease in sunflower. A total of 42 bacterial endophytes were acquired from the Department of Microbiology and Sclerotinia sclerotiorum from the Department of Plant Breeding and Genetics, Punjab Agricultural University, Ludhiana. Out of 42 bacterial isolates, four isolates exhibited antagonistic activity varying from 20.0 to 36.6% in dual plate assay and 35.4 to 92.0% in liquid media against S. sclerotiorum. The effect of bacterial endophytes on the ultrastructure of S. sclerotiorum was observed by scanning electron microscopy (SEM) which showed thinning, rupturing, breakage and shrinkage of the fungal hyphae in micrographs. In addition to antagonistic activity, bacterial endophytes also exhibited phosphate solubilization, and production of siderophores, HCN, auxins, ammonia, lipase, cellulose and amylase, while tested negative for protease, pectinase and xylanase production. Based on morphological features, biochemical test and MALDI-TOF-MS analysis, the isolates were identified as Sphingobacterium spiritivorum EB1, Bacillus sp. EB6, Pseudomonas aeruginosa EB21 and Serratia liquefaciens EB23. All the four bacterial strains exhibited ability to produce different volatile organic compounds with the highest number of VOCs produced by Bacillus sp. EB6 and the least by Pseudomonas aeruginosa EB21. The SEM analysis showed the colonization of the plant tissues by all the four bacterial strainsvalidating their endophytic nature. The bacterial treatments singly or in combinations also significantly enhanced the vigour index of sunflower ranging from 250 to 630.5. A significant increase in growth parameters, chlorophyll content, and nutrient content of shoot and soil was also observed with the bacterial treatments singly or in combinations over the uninoculated control in sunflower grown in pots in glasshouse conditions. The disease control by the bacterial treatments varied from 66.7 to 88.9%. The results indicated that the consortium of four strains was statistically not different from the consortium of SsEB1+ BaEB6 +SlEB23, indicating thereby the potential of these strains as potential biocontrol agent against Sclerotinia sclerotiorum. As the future line of recommendation, the formulation containing the consortium of these strains may be developed and tested in sunflower to control stem rot disease caused by Sclerotinia sclerotiorum in field conditions.
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Rajwinder Kaur (2023). Biological control of Sclerotinia sclerotiorum causing stem rot disease of sunflower using bacterial endophytes (Unpublished M.Sc. thesis). Punjab Agricultural University, Ludhiana, Punjab, India.