Kashyap, AnuragSaha, Ankita2024-07-192024-07-192023https://krishikosh.egranth.ac.in/handle/1/5810212237Tomato (Solanum lycopersicum L.) is one of the most important horticultural crops of the world. Its production is severely affected by bacterial wilt disease caused by Ralstonia solanacearum. This pathogenic bacterium causes wilt disease in more than 200 plant species by invading the xylem vasculature and causing death. The pathogen R. solanacearum is a ‘species complex’ consisting of races, biovars, phylotypes, sequevars, and clones (Fegan and Prior, 2005). Asian strains cluster in the Phylotype I, American strains in Phylotype II (A and B), while African and Australian-Indonesian strains group under Phylotype III and Phylotype IV, respectively. In this study, a multiplex PCR for easy and rapid detection of the phylotypes was performed, which help in easy traceability of the geographical origin of the pathogen in case of any accidental entry between countries through trade of agricultural commodities. Multiplex PCR performed using four isolated strains of R. solanacearum from different districts of Assam has revealed all of them to be of Phylotype I. Moreover, one of the most eco-friendly approaches to control bacterial wilt disease is through host resistance. The tomato cultivar Hawaii 7996 (H7996) is well known for its stable resistance against the pathogen R. solanacearum (Grimault et al., 1995). In order to unravel the underlying defence mechanism, liquid chromatography mass spectrometry (LC-MS) combined with multivariate data analysis has been used to identify the metabolites that play a crucial role in the defence mechanism of tomato against bacterial wilt. A number of secondary metabolites with varying fold changes were identified in H7996 that have been found to play pivotal role in the plant defence system. The identified metabolites were under the broad categories of flavonoids, terpenoids, saponins, glycoalkaloids, organic acids, quinone derivatives etc. Moreover, this study aimed at exploring grafting in tomato using the resistant rootstock H7996 and susceptible cultivar Marmande to check for the efficacy of grafted plants against bacterial wilt. Wilting assay following challenge inoculation of R. solanacearum showed a significantly lower progress of the disease in resistant rootstock H7996 and Marmande scion grafted plants in comparison to non-grafted Marmande plants. The colonization of R. solanacearum was also recorded in both grafted and non-grafted tomato plants which showed significant reduction of pathogen load in the scion of grafted plants in comparison with non-grafted stem, indicating grafting as a potential and sustainable tool against this dreadful disease.EnglishThesis