Phenotypic and physiological characterization of maize inbred lines resistant and susceptible to maydis leaf blight

Maydis leaf blight (MLB) caused by Cochliobolus heterostrophus is one of the most important fungal diseases of maize. A study was conducted for phenotypical characterization of ten Indian maize inbred lines, which were grouped based on phenotyping and their morpho-physiological attributes against MLB disease. On the basis of phenotyping, they were categorized into five resistant inbreds viz., SC-7-2-1-2-6-1, SC24 (92)-2-3-2-1-1, DMSC-16-2, V-351-1-4 and HKI MBR-139-2, and five susceptible inbreds viz., CM-119, DMSC-28, HKI PC-8, HKI 1040-C2 and V341. The leaf hair density was high in resistant genotypes (249.79/microscopic field, at 100×) and significantly less in susceptible genotypes (99.33/microscopic field at 100×). Stomata count was found less (6.12/microscopic field, at 400×) in resistant genotypes as compared to susceptible genotypes (10.56/microscopic field at 400×). The rate of photosynthesis was high in uninoculated control plant than in the inoculated plants. Under inoculated conditions photosynthetic rate was significantly high in resistant lines than the susceptible inbred lines which were gradually reduced with the advancement of time. The transpiration rate of inoculated plants was also higher than the control plants at 5 days after inoculation (DAI), whereas it was decreased in both inoculated and control plants at 40 DAI. Elevated level of transpiration was detected in susceptible genotypes under inoculated condition. Upon inoculation stomatal conductance was decreased with the passage of time. However, there was a differential behavior in the stomatal conductance recorded in the tested maize inbred lines under control conditions.