Biochemical response of sunflower inbred lines inoculated with Macrophomina phaseolina

Abstract

Macrophomina phaseolina, the causative agent of charcoal rot, affects a wide array of plant hosts, including sunflower. This disease thrives in warm, arid conditions, leading to symptoms such as the wilting, drying, and premature ripening of sunflower plants. This study aims to explore the biochemical responses of 15 inbred lines, each exhibiting varying levels of resistance, to uncover potential correlations between resistance levels and biochemical reactions in sunflower inbred lines. The investigation focused on: total protein content (TPC), lipid peroxidation intensity as a marker of membrane integrity (LP), reduced glutathione (GSH), superoxide-dismutase activity (SOD), and total phenolic content as antioxidant compounds (TP). These parameters were assessed 10 days following the laboratory inoculation of inbred lines with the pathogen and compared with disease severity. Correlations between resistance levels and the results of these five assays were analyzed in conjunction with disease severity observed in the inbred lines. Remarkably, after the 10-day assessment period, only the total phenolic content showed a significant positive correlation with the resistance of inbred lines (r=0.712; p<0.05). This finding identified inbred lines PB 21 and L 1 as the most resilient among the tested varieties. It was observed that different inbred lines exhibit distinct responses to M. phaseolina. However, in the majority of cases, an increase in total phenolic content was noted in sunflower plants following inoculation. This suggests a potential defensive mechanism triggered by the pathogen. Further studies can analyze more precisely into the molecular intricacies of sunflower resistance to charcoal rot and validate these findings across broader genetic backgrounds.