Salinity effects on fusarium wilt severity and tomato growth.

Abstract

The aim of the present study was to elucidate the effects of water salinity and Fusarium oxysporum f. sp. lycopersici (FOL) on tomato (cv. ‘Ventura’) growth, wilt severity and subsequent yield loss. The six salt treatments tested showed no significant effect on pathogen mycelial growth in vitro but increased sporulation was recorded with the highest NaCl doses (8 and 10 g/l). Increasing salinity stress (2 to 10 g of NaCl/l) to the inoculated tomato plants enhanced the severity of Fusarium wilt disease and resulted in a significant increase in the leaf damage index (LDI) recorded from 35 to 62 days post-planting (DPP). Moreover, the LDI noted on plants under highest salt stress (8 and 10 g of NaCl/l) was increased by 55 and 60%, respectively compared with the LDI recorded on unstressed plants. Salinity treatment in watering tomato plants (inoculated or not with FOL), from 15 DPP until the end of the assay (i.e., 62 DPP), decreased plant height by 9.7 and 35% when the salinity level varied from 2 to 10 g/l. A similar effect was noted after inoculation with FOL. The fresh and dry weights of the aerial part were generally lower with the increase in NaCl dose; these parameters were reduced by 45-50% and by 34-41% with higher salt treatments tested (8 and 10 g of NaCl/l), respectively, compared to the non-saline water. The range of decrease in root fresh and dry weights was 12-74 and 13-70%, respectively, when salinity levels were 2 and 10 g of NaCl/l, compared to the unstressed plants. Fruit fresh weight was also adversely affected by the highest NaCl doses tested (8 and 10 g/l) and was reduced by 40 and 78%, respectively compared to non-saline water. _____________________________________________________________________________________________________________