Integrated field application of T. viride, botanicals, and fungicides for managing early blight (Alternaria solani) and enhancement of plant growth, tuber nutritional quality, and potato yield

Early blight disease, incited by Alternaria solani, is the most deleterious foliar disease of potato and other solanaceous crops. Herein, to counter the early blight disease, T. viride (Tv), botanicals neem (N) and garlic (G), and fungicides flusilazole (F) and kasugamycin (K) in different combinations applied through tuber treatment (ST) and foliar spray (FS) were evaluated for disease suppression, germination percent, plant growth promotion, photosynthetic pigments, and yield components as well as the nutritional quality of tubers under field conditions during the 2018-2019 and 2019-2020 seasons. The results of two-year field experiments revealed that the combination of Tv+ F+ N (ST) + G+K (FS) efficiently suppressed the development of the early blight disease symptoms and recorded 21.63 and 18.37% disease severity (DS) as compared to untreated control, respectively at 30 days post-treatment (dpt). During the 2018-2019 seasons, potato tubers treated with Tv +F significantly increased tuber germination (97.78%), while Tv+ F+ N treated potato tubers exhibited 98.89% tuber germination during the 2019-2020 season. Additionally, the potato plants treated with the combination of Tv+ F+ N (ST) + G+K (FS) and challenge inoculated with A. solani positively increased plant growth promotion activities like shoot and root length, fresh and dry weight of shoot and root, number of branches/plant, and induced accumulation of photosynthetic pigments like chlorophyll-a, b, and total carotenoids content during both seasons. Furthermore, under A. solani inoculated conditions, treatment with Tv+ F+ N (ST) + G+K (FS) significantly increased all yield attributing traits and other parameters associated with tuber nutritional quality such as starch (1.79-and 1.68-fold, respectively), vitamin-C (1.51-and 1.58-fold, respectively), total nitrogen (1.31-and 1.33-fold, respectively), total phosphorus (1.53-and 1.60-fold, respectively), and total potassium content (1.42-and 1.45-fold, respectively) as compared to untreated control in both seasons. So, it can be concluded that among all the treatments, integrated treatment comprising of tuber treatment with T. viride, flusilazole, and neem extract + one foliar spray of garlic extract and kasugamycin was found very effective in reducing early blight disease, promoting the plant's growth, and increasing the yield as well as nutritional quality of tubers in the field conditions. The inclusive results indicated that integrated application might be a sustainable and eco-friendly control strategy for potato growers to manage potato early blight and achieve higher yields and nutritional tubers.