Effect of irrigation intervals on charcoal rot of sunflower

The experiment was conducted to observe the effect of irrigation intervals on diseases severity of charcoal rot and its consequence on growth and yield parameters of sunflower during spring season, 2015. The seeds of HO-1 sunflower variety were sown in a filed with no prior history of Macrophomina phaseolina (Tassi) presence. A 5mm diameter plug of virulent MPS16 isolate was inoculated on a stem of sunflower plant at 10 cm from soil surface when plant age was 40days. Four irrigations intervals set as treatments and equally applied in inoculated and un-inoculated plots. Maximum length of necrotic lesions (16.30±0.36cm) on stem and highest mortality percentage (13.07± 0.35) was recorded in inoculated plants of HO-1 variety received single irrigation whereas; minimum necrotic lesions (8.93 ± 0.35 cm) and lowest mortality (6.63 ± 0.19%) recorded from plots received four irrigations. Data also show significant differences in plant height and head diameter under water stress conditions. Small plants (118.10 ± 1.10 cm) and reduced head diameter (10.10 ± 0.76 cm) were produced in inoculated plants with single irrigation while, significantly tall plants (185.00 ± 1.53 cm) and increased head diameter (19.50 ± 0.76 cm) were obtained from uninoculated plants received four irrigations. 1000-seed weight and seed weight per plant also varied significantly due to different irrigation intervals. Minimum 1000-seed weight (23.90 ± 0.61 g) and seed weight per plant (25.60 ± 0.31 g) was obtained from inoculated plants of HO-1 sunflower variety given single irrigation whereas, maximum 1000-seed weight (56.00 ± 1.73 g) and seed weight per plant (63.10 ± 1.16 g) were recorded from un-inoculated plants given four irrigations. Similar pattern of yield loss was recorded in plots those were inoculated with the fungus and single irrigation while, increased yield per hectare was recorded from uninoculated plants received with four irrigations.