Pyraclostrobin can mitigate salinity stress in tomato crop

Processing tomato is a widespread crop in the Mediterranean area where often there are problems of high salinity of irrigation water with considerable harmful effects on yield. Pyraclostrobin is a strobilurin based fungicide (PBF) having a broad range of applications. Strobilurins are reported to have biostimulant effect on plant mitigating abiotic stress. Therefore, the objective of this work was to investigate the ability of PBF to improve gas exchange parameters, chlorophyll, activity of antioxidative enzymes as superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX), yield characteristics, and water use efficiency (WUE) of tomato under salinity. A two-year research was carried out in Southern Italy, on tomato cv Coronel grown in pots under plastic greenhouse, to compare two soil salinity levels (electrical conductivity, ECe = 1.1 and 5.4 dS m−1) in combination with or without PBF. As expected, salinity had harmful effects on physiological and biochemical parameters of tomato that in turn affected yield and WUE, but improved fruit quality. In fact, salinity reduced fruit mean weight (19.0%) and yield (21.4%), and increased fruit blossom-end rot (55.7%), total soluble solids (18.2%) and dry matter (18.5%) content. Overall, PBF increased leaf chlorophyll content (6.1%) and the activity of SOD, POD, CAT and APX, mainly under salinity. Moreover, it reduced stomatal conductance (12.5%) and transpiration (11.7%), but improved assimilation rate (7.8%) and intrinsic WUE (23.3%), that in turn increased yield (8.1%) and yield WUE (6.5%). The improvement in yield produced by PBF was highest in salt stressed plants. In view of the positive effects of PBF, its use should be promoted in defence programs of tomato crop, above all in areas with salinity problems.