PLANT CELL BIOTECHNOLOGY AND MOLECULAR BIOLOGY

The potato (Solanum tuberosum L.) is a member of the Solanum genus within the Solanaceae family and has a chromosome number of 2n = 48. The experiment was conducted during the Rabi season (2024–25) in the Plant Pathology Laboratory at Rama University, following a Randomized Block Design (RBD). The study involved five treatments as follows: T₁ – Inoculation with Phytophthora infestans T₂ – Inoculation with Trichoderma spp. Only T₃ – Trichoderma spp. + P. infestans (protective treatment), T₄ – Trichoderma spp. and P. infestans applied simultaneously, T₅ – Uninoculated control. Late blight of potato, caused by Phytophthora infestans, is a devastating disease that leads to major yield losses. In this study, the antagonistic activity of various Trichoderma species was evaluated both in vitro and in vivo. Dual culture assays revealed that T. harzianum (Th2) inhibited P. infestans by 95%, followed by T. asperellum (80%) and T. viride (75%). Moderate inhibition was shown by T. koningii and T. longibrachiatum. Defense enzyme activities in potato leaves were significantly enhanced by T. harzianum (T₁), with PAL activity increasing 3.6-fold at 48 hours, PO activity increasing 8.2-fold at 72 hours, and PPO activity increasing 5.4-fold at 72 hours. T. viride (T₂) and T. asperellum (T₃) also induced enzyme activity, though to a lesser extent. Plant growth under late blight stress was markedly improved by Trichoderma treatments, especially T₁, which recorded a root length of 17.8 cm, shoot length of 142.25 cm, 18.4 leaves per plant, and a dry weight of 21.80 g at 90 days after transplanting (DAT). T₂ and T₃ followed in efficacy, whereas the control (T₅) exhibited the lowest values. These results highlight T. harzianum as the most effective biocontrol agent against late blight in potato under the experimental conditions.