Influence of Symbiotic Interaction between Fungus, Virus, and Tomato Plant in Combating Drought Stress

Abstract

The influence of the three-way interaction between the fungus (Curvularia protuberata), virus (CThTV), and tomato (Solanum lycopersicum) in combating drought stress was evaluated in this study. The plants in this greenhouse experiment were grown under conditions of 400 ± 150 µmol•m −2 •s −1 photon flux density, 45% to 50% relative humidity (RH), and 30˚C ± 2˚C. Tomato seeds were germinated and inoculated with the combination of the fungus and virus at the seedling stage. The plants were allowed to grow for two weeks and randomly selected individuals were utilized. The selected plants were grown in one gallon pots containing organic potting soil. The treatments included non-symbiotic (NS), virus-free (VF), and symbiotic (An) plants. Each treatment received twelve samples and each sample was allowed to grow for an additional two weeks under drought stress. At that time, plants were exhibiting drought stress symptoms including visible wilting. Six samples from each treatment were utilized in determining selected physiological responses of tomato at pre-anthesis stage. The remaining six samples from each treatment were re-watered once and allowed to grow until they reached the anthesis stage. When they showed visible signs of wilting, the same physiological responses measured during pre-anthesis were conducted. The samples of each treatment were utilized at the end of each stage in determining photosynthetic rate, stomata conductance, photosynthetic pigments, water potential, and soluble sugar content. Plant growth, chlorophyll a, chlorophyll b, photosynthetic rate, stomata conductance, water potential, and soluble sugar content were similarly affected by the various treatments. However, carotenoids were significantly higher at pre-anthesis in the symbiotic plants in comparison to other treatments. Additionally, photosynthesis appeared to be significantly higher at anthesis compared to pre-anthesis for all treatments.