Resistance of Fifty Corn Inbred Lines to Foliar Diseases in Two Sowing Dates.

Big losses in grain yield in corn are associated with disease severity. The most effective strategy for controlling diseases is the identification and introduction of resistance genes, aiming to elaborate hybrid resistance to most diseases. The aim of this study was to attempt to identify inbred lines resistant to the following diseases: tropical rust, southern rust, gray leaf spot, northern leaf blight, physoderma brown spot and phaeosphaeria leaf spot. Fifty inbred lines derived from 4 populations (2 brachytic and 2 normal architecture) from the Corn Breeding Program of UNESP – Campus of Ilha Solteira, which had not been previously scored for these diseases, were evaluated in randomized blocks with 3 repetitions, planted on 02/20/2014 and 04/17/2014 in Selviria, MS, Brazil. This was conducted using four evaluations (grades 1-9) at 45, 60, 75 and 90 days after planting, to estimate the Area Under Disease Progress Curve (AUDPC). The joint analysis of variance had significant differences between inbred lines for tropical rust, southern rust, gray leaf spot and phaeosphaeria leaf spot. Even so, there was a significant interaction between inbred lines and seasons for both tropical rust and southern rust. In the individual analyses there were significant differences. In season 1, tropical rust, southern rust and gray leaf spot differed significantly. In season 2, significant differences occurred for southern rust and phaeosphaeria leaf spot. Based on these seasons, when there was discrimination between inbred lines for the incidence of diseases, the inbred lines with improved levels of resistance to tropical rust, southern rust and gray leaf spot were IVF1-3, IVF1-9, IVF1-10, IVF1-11, IVF1-25, IVF1-230, IVD1-2-1, IVD1-12, 2F, 3F, 6F and 4C. For phaeosphaeria leaf spot, 38 inbred lines have satisfactory resistance. For northern leaf blight and physoderma brown spot, trials in other seasons are required for efficient selection.