Abstract
Sunflower (Helianthus annuus L.) is considered as one of the most important oilseed crops in Egypt and worldwide. It is being infected with many pathogens, among these pathogens Macrophomina phaseolina (Tassi) Goid, the causal agent of charcoal rot is the most prevalent one, and responsible for severe economic losses on sunflower production. Fourteen isolates of M. phaseolina were collected from naturally infected sunflower plants. Pathogenicity tests revealed that tested isolates varied significantly in their pathogenic capabilities. But all of the tested isolates were pathogenic and incited the symptoms of pre- and post-emergence damping-off as well as symptoms of charcoal rot. In this study, antagonistic capabilities of 26 isolates of Trichoderma spp. were investigated under both laboratory and greenhouse conditions. In vitro, T. harzianum (T8) and T. hamatum (T12) proved to have high antagonistic capability against M. phaseolina fungus with inhibition percentage of 62.13% and 61.33%, respectively. Furthermore, these two isolates proved to have a high ability to control charcoal rot disease. Data of greenhouse experiments showed that application of T. harzianum (T8) and T. hamatum (T12) decreased charcoal rot disease severity by 30.33 and 24.16% respectively. Time of application played a critical role to increase the efficiency of Trichoderma spp. to control charcoal rot. In this experiment Trichoderma was implemented into soil at different application dates to study the effect of application date on the efficiency of bioagents to control charcoal rot. Results of this experiment showed that the highest reduction in disease severity occurred when T. harzianum (T8) was applied seven days before soil infestations with M. phaseolina (38.40%). Data also demonstrated that application of either T. harzianum or T. hamatum led to significant increases in the percentage of survival plants with 72.5% and 68.33%, respectively. This study suggests using Trichoderma spp could be an efficient method to control sunflower charcoal rot.