Maize hybrids performance in relation to Phaeosphaeria maydis in different sowing times

Abstract

Thirteen maize hybrids (Zea mays L.) were evaluated in relation to their response to natural infestation of Phaeosphaeria maydis, aiming to relate the disease severity with grain yield in different sowing times. Four experiments were carried out at Goianésia, GO, in randomized complete blocks design, with three replications. The hybrids were sown on four different times spaced 20 days during the maize cultivation season, begining on Dec. 5, 1994. Most hybrids used were of commercial type, including some double cross, some three-way and one single cross hybrids. It was used a visual evaluation scale for disease severity. The evaluation was performed 30 days after the flowering period. Results showed differences for yield and disease severity among the materials on different sowing period. The interaction of hybrids with sowing period was significant for the evaluated characters. The covariance analysis of yield and disease intensity allowed to affirm that on the highest infestations of Phaeosphaeria maydis the yield was affected in a negative way by the disease. In the sowing period of highest infestation the hybrids AG-1043, AGX-7391, AGX-7393 e C-901 showed to be resistant and the hybrids BR-205, AG-405, AG-510, AG-612 e G-85 showed to be susceptible.