Maize cultivars reaction to Phaeosphaeria leaf spot in São Paulo State, Brazil

Abstract

Thirty maize cultivars were evaluated for Phaeospharia leaf spot severity, in three locations in the State of São Paulo, under natural infection. The experiment included three replications of a randomized block design. Ten plants per plot were evaluated from 90 to 100 days after sowing through a scale of notes varying from 1 to 9, being 1 for 0% and 9 for more than 75% foliar area affected. In Campinas and Capão Bonito there was low disease severity (notes from 1 to 3), while in Vargem Grande do Sul high severity of Phaeosphaeria was observed, with notes from 2.0 to 6.0. From the results of Vargem Grande do Sul, SP, CO 42, IAC Taiúba, P 3041, AGM 2007, C 805, P 3051, C 425, Dina 70, C 701, Dina 170 and XL 380 were considered resistant (notes ≤ 3.0), and G 85 and AG 612 more susceptible (note 6.0). The linear correlation coefficient among notes and grain weight presented high values, negative and significant, showing that generally the Phaeosphaeria leaf spot negatively affected the yield of the evaluated cultivars. The values of temperatures and precipitation during the culture cicle indicated that the uniformity of precipitation was the most important factor in the disease development.