ETIOLOGY AND EPIDEMIOLOGICAL VARIABLES ASSOCIATED WITH MAIZE RESISTANCE TO WHITE SPOT DISEASE
F.E. Lanza, L. Zambolim, C.R. Casela, R.V. Costa, L.V. Cota, D.D. Silva, J.E.F. Figueiredo
Maize white spot disease (MWSD) has become most important in Brazil. With this study the susceptible maize hybrid DAS657 was artificially inoculated under greenhouse conditions with the bacterium Pantoea ananatis and the fungus Phaeosphaeria maydis, the two most likely candidate etiological agents of MWSD. Plants inoculated with P. ananatis reproduced the symptoms typical of MWSD, while several attempts to fulfill Koch's postulates with P. maydis failed. The epidemiological variables associated with maize resistance to MWSD was assessed with eight simple hybrids, one double hybrid, one triple hybrid and five inbred lines evaluated in two trials in a randomized block design with three replicates in two planting times. The area under disease progress curve (AUDPC) and disease severity at the end of the epidemic (Ymax) were the epidemiological variables that better differentiated maize genotypes resistant to MWSD. One inbred line and three simple hybrids were highly resistant. Two inbred lines were identified as new sources of resistance and may be used in maize breeding programs.