Dalbergia sissoo is a native tree species of the Indo-Pak subcontinent. It is one of the most common timber-producing species used in the agroforestry, fuelwood, and furniture industries. Abiotic stress, such as salinity, is known to affect the establishment of Dalbergia sissoo plantations in Pakistan. This research aimed to determine the pathogenicity of Fusarium solani on D. sissoo under three levels of salinity (EC2, EC4, and EC6 dS m-1). The seedlings were inoculated either simultaneously or predisposed to salt stress for two weeks before being subjected to fungal inoculation. High disease incidence was observed in seedlings predisposed to salinity following fungal inoculations. Controlled seedlings did not show dieback symptoms thus establishing the role of salinity predisposition in causing shisham dieback. Reduced plant growth rate and increased lesion growth were attributed to low leaf osmotic and water potential as a result of combined stresses. Photosynthetic pigments such as chlorophyll a, chlorophyll b, and carotenoids, were negatively affected. A marked increase in CAT and POD was observed which effectively lower H2O2 levels in stressed seedlings. It was concluded that abiotic stress may predispose shisham to the fungal pathogen that causes tree dieback. Therefore, it is suggested that abiotic stress remediation or the selection of the genotypes tolerant to abiotic factors would help manage shisham dieback effectively.
Keywords: Climate change; Salinity; Fungal pathogens; Host response; Shisham dieback; Salinity x pathogen interaction