Combined effect of deficit irrigation and strobilurin application on yield, fruit quality and water use efficiency of "cherry" tomato (Solanum lycopersicum L.)

This study focused on the assessment of the interactive effect of deficit irrigation and strobilurin application in improving tomato physiological and yield response under water shortage.A two-year field research (2011 and 2012) was carried out in southern Italy, on tomato grown under three irrigation regimes - full recovering of crop evapotranspiration (I100), 50% of full irrigation supply (I50) and rainfed (I0) - and with three fungicide treatments - control (F0) without any fungicide; application of fungicides without strobilurin (F1); application of a strobilurin based fungicide (Cabrio® Duo) (F2). Plant water status, yield and quality parameters, biomass and yield water use efficiency (B_WUE and Y_WUE), yield and biomass water response factors (Ky and Kby) were assessed. Water shortage significantly affected yield and quality response: as an average of the two years, a marketable yield decrement of 52.7 and 80.5% was observed in I50 and I0 in respect to I100 treatment, respectively, because of the reduction in both fruit weight and number. Fruit dry matter, total soluble solids, titratable acidity, firmness and redness showed an increase to the decline of water availability. Strobilurin based fungicide application increased total and marketable yield by 14.2% and 19.1%, respectively. In addition, strobilurin improved the plant water status under water shortage as a consequence of reduction in stomatal conductance.Deficit irrigation caused a decrease of B_WUE and Y_WUE, while the strobilurin application improved Y_WUE by 17%. Kby and Ky on average were equal to 1.11 and 1.40, respectively, and were unaffected by fungicide treatments. These results indicated the potential benefits of using strobilurin based agrochemicals in tomato disease management, due to their complementary action in improving yield, WUE, and plant water status under water stress conditions.