Effect of bixafen on senescence and yield formation of wheat

Abstract

Bixafen, a pyrazole carboxamide inhibiting succinate dehydrogenase of the fungal respiratory chain, is a new broad-spectrum fungicide developed for the control of pathogens in cereals. The effects of bixafen on senescence and yield formation of wheat plants were studied and compared to those caused by azoles, strobilurins and spiroketalamins under disease-free conditions in the greenhouse. Fungicide applications delayed the appearance and senescence of wheat ears. Application of bixafen, fluoxastrobin and prothioconazole delayed also the senescence of leaves and significantly extended the green leaf area duration compared to untreated and spiroxamine treated plants. Differences in the senescence of leaves and ears between treatments were confirmed by measurements of the temperature of wheat tissue as an indicator of transpiration activity. Digital infrared images revealed significant differences between untreated and fungicide-treated plants at different growth stages (GS). At GS 75, photosynthetic activity of untreated plants was lower compared to fungicide-treated plants; however, only bixafen gave a significant effect. All fungicide treatments increased grain yield. Application of bixafen significantly increased the yield compared to all other treatments. The temperature of ears and leaves was negatively correlated to grain yield. Lower tissue temperature of fungicide-treated plants was a suitable indicator of tissue vitality and higher photosynthetic activity due to the retardation of ear and leaf senescence. The combination of positive effects on physiology of wheat resulted in a yield advantage of bixafen-treated plants.