Analysis of yield reduction factors in processing tomatoes under waterlogging conditions

Abstract

Waterlogging conditions cause severe abiotic stress and reduce average yields in vegetable crops. Processing tomatoes are cultivated extensively worldwide, and are used in many food products. Recently, processing tomatoes have been cultivated in paddy fields in Hokkaido, northern Japan. Studies are needed to assess the responses of processing tomatoes to wet conditions. The goal of this study was to clarify the mechanisms of waterlogging injury, and to identify ways to mitigate wet injury in processing tomatoes. We used three cultivars in a two year pot experiment and a one year field experiment. Longer waterlogging treatments increased the severity of yield losses in both experiments. The waterlogging treatments initially caused reductions in fruit number and then in average fruit weight. The reductions in fruit number resulted from reduced fruiting ratios. The reductions in average fruit weight may have been triggered by multiple factors, including reductions in soil nutrients, reduced nutrient uptake due to hypoxia, and reductions in the photosynthetic rate. These results suggested that top-dressing with fertilizer after excess rain may help to mitigate yield losses. The waterlogging treatments also induced changes in fruit composition, with reduced water content and increased sugar/acid ratios. The responses to waterlogging treatment varied among cultivars, and we concluded that ‘Natsunoshun’ is a superior cultivar for cultivation in converted paddy fields that may become waterlogged after heavy rains.